doc/src/sgml/func/func-json.sgml - master - balmaster/postgres

doc/src/sgml/func/func-json.sgml
4 086 строк160 KB
Richard Guo
Fix JSON_ARRAY(query) empty set handling and view deparsing
01 май 2026, 03:42
01 май 2026, 03:428d829f5
 <sect1 id="functions-json">
  <title>JSON Functions and Operators</title>

  <indexterm zone="functions-json">
   <primary>JSON</primary>
   <secondary>functions and operators</secondary>
  </indexterm>
   <indexterm zone="functions-json">
    <primary>SQL/JSON</primary>
    <secondary>functions and expressions</secondary>
   </indexterm>

  <para>
   This section describes:

   <itemizedlist>
    <listitem>
     <para>
      functions and operators for processing and creating JSON data
     </para>
    </listitem>
    <listitem>
     <para>
      the SQL/JSON path language
     </para>
    </listitem>
    <listitem>
     <para>
      the SQL/JSON query functions
     </para>
    </listitem>
   </itemizedlist>
  </para>

  <para>
   To provide native support for JSON data types within the SQL environment,
   <productname>PostgreSQL</productname> implements the
   <firstterm>SQL/JSON data model</firstterm>.
   This model comprises sequences of items. Each item can hold SQL scalar
   values, with an additional SQL/JSON null value, and composite data structures
   that use JSON arrays and objects. The model is a formalization of the implied
   data model in the JSON specification
   <ulink url="https://datatracker.ietf.org/doc/html/rfc7159">RFC 7159</ulink>.
  </para>

  <para>
   SQL/JSON allows you to handle JSON data alongside regular SQL data,
   with transaction support, including:

  <itemizedlist>
   <listitem>
    <para>
     Uploading JSON data into the database and storing it in
     regular SQL columns as character or binary strings.
    </para>
   </listitem>
   <listitem>
    <para>
     Generating JSON objects and arrays from relational data.
    </para>
   </listitem>
   <listitem>
    <para>
     Querying JSON data using SQL/JSON query functions and
     SQL/JSON path language expressions.
    </para>
   </listitem>
  </itemizedlist>
  </para>

  <para>
   To learn more about the SQL/JSON standard, see
   <xref linkend="sqltr-19075-6"/>. For details on JSON types
   supported in <productname>PostgreSQL</productname>,
   see <xref linkend="datatype-json"/>.
  </para>

  <sect2 id="functions-json-processing">
   <title>Processing and Creating JSON Data</title>

  <para>
   <xref linkend="functions-json-op-table"/> shows the operators that
   are available for use with JSON data types (see <xref
   linkend="datatype-json"/>).
   In addition, the usual comparison operators shown in <xref
   linkend="functions-comparison-op-table"/> are available for
   <type>jsonb</type>, though not for <type>json</type>.  The comparison
   operators follow the ordering rules for B-tree operations outlined in
   <xref linkend="json-indexing"/>.
   See also <xref linkend="functions-aggregate"/> for the aggregate
   function <function>json_agg</function> which aggregates record
   values as JSON, the aggregate function
   <function>json_object_agg</function> which aggregates pairs of values
   into a JSON object, and their <type>jsonb</type> equivalents,
   <function>jsonb_agg</function> and <function>jsonb_object_agg</function>.
  </para>

  <table id="functions-json-op-table">
    <title><type>json</type> and <type>jsonb</type> Operators</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Operator
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>json</type> <literal>-&gt;</literal> <type>integer</type>
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <type>jsonb</type> <literal>-&gt;</literal> <type>integer</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Extracts <parameter>n</parameter>'th element of JSON array
        (array elements are indexed from zero, but negative integers count
        from the end).
       </para>
       <para>
        <literal>'[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -&gt; 2</literal>
        <returnvalue>{"c":"baz"}</returnvalue>
       </para>
       <para>
        <literal>'[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -&gt; -3</literal>
        <returnvalue>{"a":"foo"}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>json</type> <literal>-&gt;</literal> <type>text</type>
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <type>jsonb</type> <literal>-&gt;</literal> <type>text</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Extracts JSON object field with the given key.
       </para>
       <para>
        <literal>'{"a": {"b":"foo"}}'::json -&gt; 'a'</literal>
        <returnvalue>{"b":"foo"}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>json</type> <literal>-&gt;&gt;</literal> <type>integer</type>
        <returnvalue>text</returnvalue>
       </para>
       <para role="func_signature">
        <type>jsonb</type> <literal>-&gt;&gt;</literal> <type>integer</type>
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Extracts <parameter>n</parameter>'th element of JSON array,
        as <type>text</type>.
       </para>
       <para>
        <literal>'[1,2,3]'::json -&gt;&gt; 2</literal>
        <returnvalue>3</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>json</type> <literal>-&gt;&gt;</literal> <type>text</type>
        <returnvalue>text</returnvalue>
       </para>
       <para role="func_signature">
        <type>jsonb</type> <literal>-&gt;&gt;</literal> <type>text</type>
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Extracts JSON object field with the given key, as <type>text</type>.
       </para>
       <para>
        <literal>'{"a":1,"b":2}'::json -&gt;&gt; 'b'</literal>
        <returnvalue>2</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>json</type> <literal>#&gt;</literal> <type>text[]</type>
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <type>jsonb</type> <literal>#&gt;</literal> <type>text[]</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Extracts JSON sub-object at the specified path, where path elements
        can be either field keys or array indexes.
       </para>
       <para>
        <literal>'{"a": {"b": ["foo","bar"]}}'::json #&gt; '{a,b,1}'</literal>
        <returnvalue>"bar"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>json</type> <literal>#&gt;&gt;</literal> <type>text[]</type>
        <returnvalue>text</returnvalue>
       </para>
       <para role="func_signature">
        <type>jsonb</type> <literal>#&gt;&gt;</literal> <type>text[]</type>
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Extracts JSON sub-object at the specified path as <type>text</type>.
       </para>
       <para>
        <literal>'{"a": {"b": ["foo","bar"]}}'::json #&gt;&gt; '{a,b,1}'</literal>
        <returnvalue>bar</returnvalue>
       </para></entry>
      </row>
     </tbody>
    </tgroup>
   </table>

  <note>
   <para>
    The field/element/path extraction operators return NULL, rather than
    failing, if the JSON input does not have the right structure to match
    the request; for example if no such key or array element exists.
   </para>
  </note>

  <para>
   Some further operators exist only for <type>jsonb</type>, as shown
   in <xref linkend="functions-jsonb-op-table"/>.
   <xref linkend="json-indexing"/>
   describes how these operators can be used to effectively search indexed
   <type>jsonb</type> data.
  </para>

  <table id="functions-jsonb-op-table">
    <title>Additional <type>jsonb</type> Operators</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Operator
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>@&gt;</literal> <type>jsonb</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Does the first JSON value contain the second?
        (See <xref linkend="json-containment"/> for details about containment.)
       </para>
       <para>
        <literal>'{"a":1, "b":2}'::jsonb &#64;&gt; '{"b":2}'::jsonb</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>&lt;@</literal> <type>jsonb</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Is the first JSON value contained in the second?
       </para>
       <para>
        <literal>'{"b":2}'::jsonb &lt;@ '{"a":1, "b":2}'::jsonb</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>?</literal> <type>text</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Does the text string exist as a top-level key or array element within
        the JSON value?
       </para>
       <para>
        <literal>'{"a":1, "b":2}'::jsonb ? 'b'</literal>
        <returnvalue>t</returnvalue>
       </para>
       <para>
        <literal>'["a", "b", "c"]'::jsonb ? 'b'</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>?|</literal> <type>text[]</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Do any of the strings in the text array exist as top-level keys or
        array elements?
       </para>
       <para>
        <literal>'{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'd']</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>?&amp;</literal> <type>text[]</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Do all of the strings in the text array exist as top-level keys or
        array elements?
       </para>
       <para>
        <literal>'["a", "b", "c"]'::jsonb ?&amp; array['a', 'b']</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>||</literal> <type>jsonb</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Concatenates two <type>jsonb</type> values.
        Concatenating two arrays generates an array containing all the
        elements of each input.  Concatenating two objects generates an
        object containing the union of their
        keys, taking the second object's value when there are duplicate keys.
        All other cases are treated by converting a non-array input into a
        single-element array, and then proceeding as for two arrays.
        Does not operate recursively: only the top-level array or object
        structure is merged.
       </para>
       <para>
        <literal>'["a", "b"]'::jsonb || '["a", "d"]'::jsonb</literal>
        <returnvalue>["a", "b", "a", "d"]</returnvalue>
       </para>
       <para>
        <literal>'{"a": "b"}'::jsonb || '{"c": "d"}'::jsonb</literal>
        <returnvalue>{"a": "b", "c": "d"}</returnvalue>
       </para>
       <para>
        <literal>'[1, 2]'::jsonb || '3'::jsonb</literal>
        <returnvalue>[1, 2, 3]</returnvalue>
       </para>
       <para>
        <literal>'{"a": "b"}'::jsonb || '42'::jsonb</literal>
        <returnvalue>[{"a": "b"}, 42]</returnvalue>
       </para>
       <para>
        To append an array to another array as a single entry, wrap it
        in an additional layer of array, for example:
       </para>
       <para>
        <literal>'[1, 2]'::jsonb || jsonb_build_array('[3, 4]'::jsonb)</literal>
        <returnvalue>[1, 2, [3, 4]]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>-</literal> <type>text</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Deletes a key (and its value) from a JSON object, or matching string
        value(s) from a JSON array.
       </para>
       <para>
        <literal>'{"a": "b", "c": "d"}'::jsonb - 'a'</literal>
        <returnvalue>{"c": "d"}</returnvalue>
       </para>
       <para>
        <literal>'["a", "b", "c", "b"]'::jsonb - 'b'</literal>
        <returnvalue>["a", "c"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>-</literal> <type>text[]</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Deletes all matching keys or array elements from the left operand.
       </para>
       <para>
        <literal>'{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[]</literal>
        <returnvalue>{}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>-</literal> <type>integer</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Deletes the array element with specified index (negative
        integers count from the end).  Throws an error if JSON value
        is not an array.
       </para>
       <para>
        <literal>'["a", "b"]'::jsonb - 1 </literal>
        <returnvalue>["a"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>#-</literal> <type>text[]</type>
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Deletes the field or array element at the specified path, where path
        elements can be either field keys or array indexes.
       </para>
       <para>
        <literal>'["a", {"b":1}]'::jsonb #- '{1,b}'</literal>
        <returnvalue>["a", {}]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>@?</literal> <type>jsonpath</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Does JSON path return any item for the specified JSON value?
        (This is useful only with SQL-standard JSON path expressions, not
        <link linkend="functions-sqljson-check-expressions">predicate check
        expressions</link>, since those always return a value.)
       </para>
       <para>
        <literal>'{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)'</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <type>jsonb</type> <literal>@@</literal> <type>jsonpath</type>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Returns the result of a JSON path predicate check for the
        specified JSON value.
        (This is useful only
        with <link linkend="functions-sqljson-check-expressions">predicate
        check expressions</link>, not SQL-standard JSON path expressions,
        since it will return <literal>NULL</literal> if the path result is
        not a single boolean value.)
       </para>
       <para>
        <literal>'{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2'</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>
     </tbody>
    </tgroup>
   </table>

  <note>
   <para>
    The <type>jsonpath</type> operators <literal>@?</literal>
    and <literal>@@</literal> suppress the following errors: missing object
    field or array element, unexpected JSON item type, datetime and numeric
    errors.  The <type>jsonpath</type>-related functions described below can
    also be told to suppress these types of errors.  This behavior might be
    helpful when searching JSON document collections of varying structure.
   </para>
  </note>

  <para>
   <xref linkend="functions-json-creation-table"/> shows the functions that are
   available for constructing <type>json</type> and <type>jsonb</type> values.
   Some functions in this table have a <literal>RETURNING</literal> clause,
   which specifies the data type returned.  It must be one of <type>json</type>,
   <type>jsonb</type>, <type>bytea</type>, a character string type (<type>text</type>,
   <type>char</type>, or <type>varchar</type>), or a type
   that can be cast to <type>json</type>.
   By default, the <type>json</type> type is returned.
  </para>

  <table id="functions-json-creation-table">
    <title>JSON Creation Functions</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Function
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>to_json</primary>
        </indexterm>
        <function>to_json</function> ( <type>anyelement</type> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>to_jsonb</primary>
        </indexterm>
        <function>to_jsonb</function> ( <type>anyelement</type> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Converts any SQL value to <type>json</type> or <type>jsonb</type>.
        Arrays and composites are converted recursively to arrays and
        objects (multidimensional arrays become arrays of arrays in JSON).
        Otherwise, if there is a cast from the SQL data type
        to <type>json</type>, the cast function will be used to perform the
        conversion;<footnote>
         <para>
          For example, the <xref linkend="hstore"/> extension has a cast
          from <type>hstore</type> to <type>json</type>, so that
          <type>hstore</type> values converted via the JSON creation functions
          will be represented as JSON objects, not as primitive string values.
         </para>
        </footnote>
        otherwise, a scalar JSON value is produced.  For any scalar other than
        a number, a Boolean, or a null value, the text representation will be
        used, with escaping as necessary to make it a valid JSON string value.
       </para>
       <para>
        <literal>to_json('Fred said "Hi."'::text)</literal>
        <returnvalue>"Fred said \"Hi.\""</returnvalue>
       </para>
       <para>
        <literal>to_jsonb(row(42, 'Fred said "Hi."'::text))</literal>
        <returnvalue>{"f1": 42, "f2": "Fred said \"Hi.\""}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>array_to_json</primary>
        </indexterm>
        <function>array_to_json</function> ( <type>anyarray</type> <optional>, <type>boolean</type> </optional> )
        <returnvalue>json</returnvalue>
       </para>
       <para>
        Converts an SQL array to a JSON array.  The behavior is the same
        as <function>to_json</function> except that line feeds will be added
        between top-level array elements if the optional boolean parameter is
        true.
       </para>
       <para>
        <literal>array_to_json('{{1,5},{99,100}}'::int[])</literal>
        <returnvalue>[[1,5],[99,100]]</returnvalue>
       </para></entry>
      </row>

      <row>
       <!--
           Note that this is barely legible in the output; it looks like a
           salad of braces and brackets.  It would be better to split it out
           in multiple lines, but that's surprisingly hard to do in a way that
           matches in HTML and PDF output.  Other standard SQL/JSON functions
           have the same problem.
         -->
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm><primary>json_array</primary></indexterm>
         <function>json_array</function> (
         <optional> { <replaceable>value_expression</replaceable> <optional> <literal>FORMAT JSON</literal> </optional> } <optional>, ...</optional> </optional>
         <optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
         <optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
        </para>
        <para role="func_signature">
         <function>json_array</function> (
         <optional> <replaceable>query_expression</replaceable> </optional>
         <optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
        </para>
        <para>
         Constructs a JSON array from either a series of
         <replaceable>value_expression</replaceable> parameters or from the results
         of <replaceable>query_expression</replaceable>,
         which must be a SELECT query returning a single column. If
         <literal>ABSENT ON NULL</literal> is specified, NULL values are ignored.
         This is always the case if a
         <replaceable>query_expression</replaceable> is used. If the query returns
         no rows, an empty JSON array is returned.
        </para>
        <para>
         <literal>json_array(1,true,json '{"a":null}')</literal>
         <returnvalue>[1, true, {"a":null}]</returnvalue>
        </para>
        <para>
         <literal>json_array(SELECT * FROM (VALUES(1),(2)) t)</literal>
         <returnvalue>[1, 2]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>row_to_json</primary>
        </indexterm>
        <function>row_to_json</function> ( <type>record</type> <optional>, <type>boolean</type> </optional> )
        <returnvalue>json</returnvalue>
       </para>
       <para>
        Converts an SQL composite value to a JSON object.  The behavior is the
        same as <function>to_json</function> except that line feeds will be
        added between top-level elements if the optional boolean parameter is
        true.
       </para>
       <para>
        <literal>row_to_json(row(1,'foo'))</literal>
        <returnvalue>{"f1":1,"f2":"foo"}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_build_array</primary>
        </indexterm>
        <function>json_build_array</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_build_array</primary>
        </indexterm>
        <function>jsonb_build_array</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Builds a possibly-heterogeneously-typed JSON array out of a variadic
        argument list.  Each argument is converted as
        per <function>to_json</function> or <function>to_jsonb</function>.
       </para>
       <para>
        <literal>json_build_array(1, 2, 'foo', 4, 5)</literal>
        <returnvalue>[1, 2, "foo", 4, 5]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_build_object</primary>
        </indexterm>
        <function>json_build_object</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_build_object</primary>
        </indexterm>
        <function>jsonb_build_object</function> ( <literal>VARIADIC</literal> <type>"any"</type> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Builds a JSON object out of a variadic argument list.  By convention,
        the argument list consists of alternating keys and values.  Key
        arguments are coerced to text; value arguments are converted as
        per <function>to_json</function> or <function>to_jsonb</function>.
       </para>
       <para>
        <literal>json_build_object('foo', 1, 2, row(3,'bar'))</literal>
        <returnvalue>{"foo" : 1, "2" : {"f1":3,"f2":"bar"}}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
         <indexterm><primary>json_object</primary></indexterm>
         <function>json_object</function> (
         <optional> { <replaceable>key_expression</replaceable> { <literal>VALUE</literal> | ':' }
          <replaceable>value_expression</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> }<optional>, ...</optional> </optional>
         <optional> { <literal>NULL</literal> | <literal>ABSENT</literal> } <literal>ON NULL</literal> </optional>
         <optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
         <optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>)
        </para>
        <para>
         Constructs a JSON object of all the key/value pairs given,
         or an empty object if none are given.
         <replaceable>key_expression</replaceable> is a scalar expression
         defining the <acronym>JSON</acronym> key, which is
         converted to the <type>text</type> type.
         It cannot be <literal>NULL</literal> nor can it
         belong to a type that has a cast to the <type>json</type> type.
         If <literal>WITH UNIQUE KEYS</literal> is specified, there must not
         be any duplicate <replaceable>key_expression</replaceable>.
         Any pair for which the <replaceable>value_expression</replaceable>
         evaluates to <literal>NULL</literal> is omitted from the output
         if <literal>ABSENT ON NULL</literal> is specified;
         if <literal>NULL ON NULL</literal> is specified or the clause
         omitted, the key is included with value <literal>NULL</literal>.
        </para>
        <para>
         <literal>json_object('code' VALUE 'P123', 'title': 'Jaws')</literal>
         <returnvalue>{"code" : "P123", "title" : "Jaws"}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_object</primary>
        </indexterm>
        <function>json_object</function> ( <type>text[]</type> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_object</primary>
        </indexterm>
        <function>jsonb_object</function> ( <type>text[]</type> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Builds a JSON object out of a text array.  The array must have either
        exactly one dimension with an even number of members, in which case
        they are taken as alternating key/value pairs, or two dimensions
        such that each inner array has exactly two elements, which
        are taken as a key/value pair.  All values are converted to JSON
        strings.
       </para>
       <para>
        <literal>json_object('{a, 1, b, "def", c, 3.5}')</literal>
        <returnvalue>{"a" : "1", "b" : "def", "c" : "3.5"}</returnvalue>
       </para>
        <para><literal>json_object('{{a, 1}, {b, "def"}, {c, 3.5}}')</literal>
        <returnvalue>{"a" : "1", "b" : "def", "c" : "3.5"}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <function>json_object</function> ( <parameter>keys</parameter> <type>text[]</type>, <parameter>values</parameter> <type>text[]</type> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <function>jsonb_object</function> ( <parameter>keys</parameter> <type>text[]</type>, <parameter>values</parameter> <type>text[]</type> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        This form of <function>json_object</function> takes keys and values
        pairwise from separate text arrays.  Otherwise it is identical to
        the one-argument form.
       </para>
       <para>
        <literal>json_object('{a,b}', '{1,2}')</literal>
        <returnvalue>{"a": "1", "b": "2"}</returnvalue>
       </para></entry>
      </row>
      <row>
       <entry role="func_table_entry">
        <para role="func_signature">
         <indexterm><primary>json constructor</primary></indexterm>
         <function>json</function> (
         <replaceable>expression</replaceable>
         <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional></optional>
         <optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional></optional> )
         <returnvalue>json</returnvalue>
        </para>
        <para>
         Converts a given expression specified as <type>text</type> or
         <type>bytea</type> string (in UTF8 encoding) into a JSON
         value.  If <replaceable>expression</replaceable> is NULL, an
         <acronym>SQL</acronym> null value is returned.
         If <literal>WITH UNIQUE</literal> is specified, the
         <replaceable>expression</replaceable> must not contain any duplicate
         object keys.
        </para>
        <para>
         <literal>json('{"a":123, "b":[true,"foo"], "a":"bar"}')</literal>
         <returnvalue>{"a":123, "b":[true,"foo"], "a":"bar"}</returnvalue>
        </para>
       </entry>
      </row>
      <row>
       <entry role="func_table_entry">
        <para role="func_signature">
        <indexterm><primary>json_scalar</primary></indexterm>
        <function>json_scalar</function> ( <replaceable>expression</replaceable> )
       </para>
       <para>
        Converts a given SQL scalar value into a JSON scalar value.
        If the input is NULL, an <acronym>SQL</acronym> null is returned. If
        the input is number or a boolean value, a corresponding JSON number
        or boolean value is returned. For any other value, a JSON string is
        returned.
       </para>
       <para>
        <literal>json_scalar(123.45)</literal>
        <returnvalue>123.45</returnvalue>
       </para>
       <para>
        <literal>json_scalar(CURRENT_TIMESTAMP)</literal>
        <returnvalue>"2022-05-10T10:51:04.62128-04:00"</returnvalue>
      </para></entry>
     </row>
     <row>
      <entry role="func_table_entry">
       <para role="func_signature">
        <function>json_serialize</function> (
        <replaceable>expression</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional>
        <optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional> )
       </para>
       <para>
        Converts an SQL/JSON expression into a character or binary string. The
        <replaceable>expression</replaceable> can be of any JSON type, any
        character string type, or <type>bytea</type> in UTF8 encoding.
        The returned type used in <literal> RETURNING</literal> can be any
        character string type or <type>bytea</type>. The default is
        <type>text</type>.
       </para>
       <para>
        <literal>json_serialize('{ "a" : 1 } ' RETURNING bytea)</literal>
        <returnvalue>\x7b20226122203a2031207d20</returnvalue>
      </para></entry>
     </row>
     </tbody>
    </tgroup>
   </table>

  <para>
   <xref linkend="functions-sqljson-misc" /> details SQL/JSON
   facilities for testing JSON.
  </para>

  <table id="functions-sqljson-misc">
   <title>SQL/JSON Testing Functions</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="func_table_entry"><para role="func_signature">
        Function signature
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
      </para></entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry role="func_table_entry"><para role="func_signature">
        <indexterm><primary>IS JSON</primary></indexterm>
        <replaceable>expression</replaceable> <literal>IS</literal> <optional> <literal>NOT</literal> </optional> <literal>JSON</literal>
        <optional> { <literal>VALUE</literal> | <literal>SCALAR</literal> | <literal>ARRAY</literal> | <literal>OBJECT</literal> } </optional>
        <optional> { <literal>WITH</literal> | <literal>WITHOUT</literal> } <literal>UNIQUE</literal> <optional> <literal>KEYS</literal> </optional> </optional>
       </para>
       <para>
        This predicate tests whether <replaceable>expression</replaceable> can be
        parsed as JSON, possibly of a specified type.
        If <literal>SCALAR</literal> or <literal>ARRAY</literal> or
        <literal>OBJECT</literal> is specified, the
        test is whether or not the JSON is of that particular type. If
        <literal>WITH UNIQUE KEYS</literal> is specified, then any object in the
        <replaceable>expression</replaceable> is also tested to see if it
        has duplicate keys.
       </para>
       <para>
<programlisting>
SELECT js,
  js IS JSON "json?",
  js IS JSON SCALAR "scalar?",
  js IS JSON OBJECT "object?",
  js IS JSON ARRAY "array?"
FROM (VALUES
      ('123'), ('"abc"'), ('{"a": "b"}'), ('[1,2]'),('abc')) foo(js);
     js     | json? | scalar? | object? | array?
------------+-------+---------+---------+--------
 123        | t     | t       | f       | f
 "abc"      | t     | t       | f       | f
 {"a": "b"} | t     | f       | t       | f
 [1,2]      | t     | f       | f       | t
 abc        | f     | f       | f       | f
</programlisting>
       </para>
       <para>
<programlisting>
SELECT js,
  js IS JSON OBJECT "object?",
  js IS JSON ARRAY "array?",
  js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?",
  js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?"
FROM (VALUES ('[{"a":"1"},
 {"b":"2","b":"3"}]')) foo(js);
-[ RECORD 1 ]-+--------------------
js            | [{"a":"1"},        +
              |  {"b":"2","b":"3"}]
object?       | f
array?        | t
array w. UK?  | f
array w/o UK? | t
</programlisting>
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   <xref linkend="functions-json-processing-table"/> shows the functions that
   are available for processing <type>json</type> and <type>jsonb</type> values.
  </para>

  <table id="functions-json-processing-table">
    <title>JSON Processing Functions</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Function
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_array_elements</primary>
        </indexterm>
        <function>json_array_elements</function> ( <type>json</type> )
        <returnvalue>setof json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_array_elements</primary>
        </indexterm>
        <function>jsonb_array_elements</function> ( <type>jsonb</type> )
        <returnvalue>setof jsonb</returnvalue>
       </para>
       <para>
        Expands the top-level JSON array into a set of JSON values.
       </para>
       <para>
        <literal>SELECT * FROM json_array_elements('[1,true, [2,false]]')</literal>
        <returnvalue></returnvalue>
<programlisting>
   value
-----------
 1
 true
 [2,false]
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_array_elements_text</primary>
        </indexterm>
        <function>json_array_elements_text</function> ( <type>json</type> )
        <returnvalue>setof text</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_array_elements_text</primary>
        </indexterm>
        <function>jsonb_array_elements_text</function> ( <type>jsonb</type> )
        <returnvalue>setof text</returnvalue>
       </para>
       <para>
        Expands the top-level JSON array into a set of <type>text</type> values.
       </para>
       <para>
        <literal>SELECT * FROM json_array_elements_text('["foo", "bar"]')</literal>
        <returnvalue></returnvalue>
<programlisting>
   value
-----------
 foo
 bar
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_array_length</primary>
        </indexterm>
        <function>json_array_length</function> ( <type>json</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_array_length</primary>
        </indexterm>
        <function>jsonb_array_length</function> ( <type>jsonb</type> )
        <returnvalue>integer</returnvalue>
       </para>
       <para>
        Returns the number of elements in the top-level JSON array.
       </para>
       <para>
        <literal>json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]')</literal>
        <returnvalue>5</returnvalue>
       </para>
       <para>
        <literal>jsonb_array_length('[]')</literal>
        <returnvalue>0</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_each</primary>
        </indexterm>
        <function>json_each</function> ( <type>json</type> )
        <returnvalue>setof record</returnvalue>
        ( <parameter>key</parameter> <type>text</type>,
        <parameter>value</parameter> <type>json</type> )
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_each</primary>
        </indexterm>
        <function>jsonb_each</function> ( <type>jsonb</type> )
        <returnvalue>setof record</returnvalue>
        ( <parameter>key</parameter> <type>text</type>,
        <parameter>value</parameter> <type>jsonb</type> )
       </para>
       <para>
        Expands the top-level JSON object into a set of key/value pairs.
       </para>
       <para>
        <literal>SELECT * FROM json_each('{"a":"foo", "b":"bar"}')</literal>
        <returnvalue></returnvalue>
<programlisting>
 key | value
-----+-------
 a   | "foo"
 b   | "bar"
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_each_text</primary>
        </indexterm>
        <function>json_each_text</function> ( <type>json</type> )
        <returnvalue>setof record</returnvalue>
        ( <parameter>key</parameter> <type>text</type>,
        <parameter>value</parameter> <type>text</type> )
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_each_text</primary>
        </indexterm>
        <function>jsonb_each_text</function> ( <type>jsonb</type> )
        <returnvalue>setof record</returnvalue>
        ( <parameter>key</parameter> <type>text</type>,
        <parameter>value</parameter> <type>text</type> )
       </para>
       <para>
        Expands the top-level JSON object into a set of key/value pairs.
        The returned <parameter>value</parameter>s will be of
        type <type>text</type>.
       </para>
       <para>
        <literal>SELECT * FROM json_each_text('{"a":"foo", "b":"bar"}')</literal>
        <returnvalue></returnvalue>
<programlisting>
 key | value
-----+-------
 a   | foo
 b   | bar
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_extract_path</primary>
        </indexterm>
        <function>json_extract_path</function> ( <parameter>from_json</parameter> <type>json</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_extract_path</primary>
        </indexterm>
        <function>jsonb_extract_path</function> ( <parameter>from_json</parameter> <type>jsonb</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Extracts JSON sub-object at the specified path.
        (This is functionally equivalent to the <literal>#&gt;</literal>
        operator, but writing the path out as a variadic list can be more
        convenient in some cases.)
       </para>
       <para>
        <literal>json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6')</literal>
        <returnvalue>"foo"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_extract_path_text</primary>
        </indexterm>
        <function>json_extract_path_text</function> ( <parameter>from_json</parameter> <type>json</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_extract_path_text</primary>
        </indexterm>
        <function>jsonb_extract_path_text</function> ( <parameter>from_json</parameter> <type>jsonb</type>, <literal>VARIADIC</literal> <parameter>path_elems</parameter> <type>text[]</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Extracts JSON sub-object at the specified path as <type>text</type>.
        (This is functionally equivalent to the <literal>#&gt;&gt;</literal>
        operator.)
       </para>
       <para>
        <literal>json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6')</literal>
        <returnvalue>foo</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_object_keys</primary>
        </indexterm>
        <function>json_object_keys</function> ( <type>json</type> )
        <returnvalue>setof text</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_object_keys</primary>
        </indexterm>
        <function>jsonb_object_keys</function> ( <type>jsonb</type> )
        <returnvalue>setof text</returnvalue>
       </para>
       <para>
        Returns the set of keys in the top-level JSON object.
       </para>
       <para>
        <literal>SELECT * FROM json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}')</literal>
        <returnvalue></returnvalue>
<programlisting>
 json_object_keys
------------------
 f1
 f2
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_populate_record</primary>
        </indexterm>
        <function>json_populate_record</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>json</type> )
        <returnvalue>anyelement</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_populate_record</primary>
        </indexterm>
        <function>jsonb_populate_record</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>jsonb</type> )
        <returnvalue>anyelement</returnvalue>
       </para>
       <para>
        Expands the top-level JSON object to a row having the composite type
        of the <parameter>base</parameter> argument.  The JSON object
        is scanned for fields whose names match column names of the output row
        type, and their values are inserted into those columns of the output.
        (Fields that do not correspond to any output column name are ignored.)
        In typical use, the value of <parameter>base</parameter> is just
        <literal>NULL</literal>, which means that any output columns that do
        not match any object field will be filled with nulls.  However,
        if <parameter>base</parameter> isn't <literal>NULL</literal> then
        the values it contains will be used for unmatched columns.
       </para>
       <para>
        To convert a JSON value to the SQL type of an output column, the
        following rules are applied in sequence:
        <itemizedlist spacing="compact">
         <listitem>
          <para>
           A JSON null value is converted to an SQL null in all cases.
          </para>
         </listitem>
         <listitem>
          <para>
           If the output column is of type <type>json</type>
           or <type>jsonb</type>, the JSON value is just reproduced exactly.
          </para>
         </listitem>
         <listitem>
          <para>
           If the output column is a composite (row) type, and the JSON value
           is a JSON object, the fields of the object are converted to columns
           of the output row type by recursive application of these rules.
          </para>
         </listitem>
         <listitem>
          <para>
           Likewise, if the output column is an array type and the JSON value
           is a JSON array, the elements of the JSON array are converted to
           elements of the output array by recursive application of these
           rules.
          </para>
         </listitem>
         <listitem>
          <para>
           Otherwise, if the JSON value is a string, the contents of the
           string are fed to the input conversion function for the column's
           data type.
          </para>
         </listitem>
         <listitem>
          <para>
           Otherwise, the ordinary text representation of the JSON value is
           fed to the input conversion function for the column's data type.
          </para>
         </listitem>
        </itemizedlist>
       </para>
       <para>
        While the example below uses a constant JSON value, typical use would
        be to reference a <type>json</type> or <type>jsonb</type> column
        laterally from another table in the query's <literal>FROM</literal>
        clause.  Writing <function>json_populate_record</function> in
        the <literal>FROM</literal> clause is good practice, since all of the
        extracted columns are available for use without duplicate function
        calls.
       </para>
       <para>
        <literal>CREATE TYPE subrowtype AS (d int, e text);</literal>
        <literal>CREATE TYPE myrowtype AS (a int, b text[], c subrowtype);</literal>
       </para>
       <para>
        <literal>SELECT * FROM json_populate_record(NULL::myrowtype,
         '{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "a  b c"}, "x": "foo"}')</literal>
        <returnvalue></returnvalue>
<programlisting>
 a |   b       |      c
---+-----------+-------------
 1 | {2,"a b"} | (4,"a b c")
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_populate_record_valid</primary>
        </indexterm>
        <function>jsonb_populate_record_valid</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>json</type> )
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Function for testing <function>jsonb_populate_record</function>.  Returns
        <literal>true</literal> if the input <function>jsonb_populate_record</function>
        would finish without an error for the given input JSON object; that is, it's
        valid input, <literal>false</literal> otherwise.
       </para>
       <para>
        <literal>CREATE TYPE jsb_char2 AS (a char(2));</literal>
       </para>
       <para>
        <literal>SELECT jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aaa"}');</literal>
        <returnvalue></returnvalue>
<programlisting>
 jsonb_populate_record_valid
-----------------------------
 f
(1 row)
</programlisting>

        <literal>SELECT * FROM jsonb_populate_record(NULL::jsb_char2, '{"a": "aaa"}') q;</literal>
        <returnvalue></returnvalue>
<programlisting>
ERROR:  value too long for type character(2)
</programlisting>
        <literal>SELECT jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aa"}');</literal>
        <returnvalue></returnvalue>
<programlisting>
 jsonb_populate_record_valid
-----------------------------
 t
(1 row)
</programlisting>

        <literal>SELECT * FROM jsonb_populate_record(NULL::jsb_char2, '{"a": "aa"}') q;</literal>
        <returnvalue></returnvalue>
<programlisting>
 a
----
 aa
(1 row)
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_populate_recordset</primary>
        </indexterm>
        <function>json_populate_recordset</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>json</type> )
        <returnvalue>setof anyelement</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_populate_recordset</primary>
        </indexterm>
        <function>jsonb_populate_recordset</function> ( <parameter>base</parameter> <type>anyelement</type>, <parameter>from_json</parameter> <type>jsonb</type> )
        <returnvalue>setof anyelement</returnvalue>
       </para>
       <para>
        Expands the top-level JSON array of objects to a set of rows having
        the composite type of the <parameter>base</parameter> argument.
        Each element of the JSON array is processed as described above
        for <function>json[b]_populate_record</function>.
       </para>
       <para>
        <literal>CREATE TYPE twoints AS (a int, b int);</literal>
       </para>
       <para>
        <literal>SELECT * FROM json_populate_recordset(NULL::twoints, '[{"a":1,"b":2}, {"a":3,"b":4}]')</literal>
        <returnvalue></returnvalue>
<programlisting>
 a | b
---+---
 1 | 2
 3 | 4
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_to_record</primary>
        </indexterm>
        <function>json_to_record</function> ( <type>json</type> )
        <returnvalue>record</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_to_record</primary>
        </indexterm>
        <function>jsonb_to_record</function> ( <type>jsonb</type> )
        <returnvalue>record</returnvalue>
       </para>
       <para>
        Expands the top-level JSON object to a row having the composite type
        defined by an <literal>AS</literal> clause.  (As with all functions
        returning <type>record</type>, the calling query must explicitly
        define the structure of the record with an <literal>AS</literal>
        clause.)  The output record is filled from fields of the JSON object,
        in the same way as described above
        for <function>json[b]_populate_record</function>.  Since there is no
        input record value, unmatched columns are always filled with nulls.
       </para>
       <para>
        <literal>CREATE TYPE myrowtype AS (a int, b text);</literal>
       </para>
       <para>
        <literal>SELECT * FROM json_to_record('{"a":1,"b":[1,2,3],"c":[1,2,3],"e":"bar","r": {"a": 123, "b": "a b c"}}') AS x(a int, b text, c int[], d text, r myrowtype)</literal>
        <returnvalue></returnvalue>
<programlisting>
 a |    b    |    c    | d |       r
---+---------+---------+---+---------------
 1 | [1,2,3] | {1,2,3} |   | (123,"a b c")
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_to_recordset</primary>
        </indexterm>
        <function>json_to_recordset</function> ( <type>json</type> )
        <returnvalue>setof record</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_to_recordset</primary>
        </indexterm>
        <function>jsonb_to_recordset</function> ( <type>jsonb</type> )
        <returnvalue>setof record</returnvalue>
       </para>
       <para>
        Expands the top-level JSON array of objects to a set of rows having
        the composite type defined by an <literal>AS</literal> clause.  (As
        with all functions returning <type>record</type>, the calling query
        must explicitly define the structure of the record with
        an <literal>AS</literal> clause.)  Each element of the JSON array is
        processed as described above
        for <function>json[b]_populate_record</function>.
       </para>
       <para>
        <literal>SELECT * FROM json_to_recordset('[{"a":1,"b":"foo"}, {"a":"2","c":"bar"}]') AS x(a int, b text)</literal>
        <returnvalue></returnvalue>
<programlisting>
 a |  b
---+-----
 1 | foo
 2 |
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_set</primary>
        </indexterm>
        <function>jsonb_set</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>text[]</type>, <parameter>new_value</parameter> <type>jsonb</type> <optional>, <parameter>create_if_missing</parameter> <type>boolean</type> </optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Returns <parameter>target</parameter>
        with the item designated by <parameter>path</parameter>
        replaced by <parameter>new_value</parameter>, or with
        <parameter>new_value</parameter> added if
        <parameter>create_if_missing</parameter> is true (which is the
        default) and the item designated by <parameter>path</parameter>
        does not exist.
        All earlier steps in the path must exist, or
        the <parameter>target</parameter> is returned unchanged.
        As with the path oriented operators, negative integers that
        appear in the <parameter>path</parameter> count from the end
        of JSON arrays.
        If the last path step is an array index that is out of range,
        and <parameter>create_if_missing</parameter> is true, the new
        value is added at the beginning of the array if the index is negative,
        or at the end of the array if it is positive.
       </para>
       <para>
        <literal>jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', '[2,3,4]', false)</literal>
        <returnvalue>[{"f1": [2, 3, 4], "f2": null}, 2, null, 3]</returnvalue>
       </para>
       <para>
        <literal>jsonb_set('[{"f1":1,"f2":null},2]', '{0,f3}', '[2,3,4]')</literal>
        <returnvalue>[{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_set_lax</primary>
        </indexterm>
        <function>jsonb_set_lax</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>text[]</type>, <parameter>new_value</parameter> <type>jsonb</type> <optional>, <parameter>create_if_missing</parameter> <type>boolean</type> <optional>, <parameter>null_value_treatment</parameter> <type>text</type> </optional></optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        If <parameter>new_value</parameter> is not <literal>NULL</literal>,
        behaves identically to <literal>jsonb_set</literal>. Otherwise behaves
        according to the value
        of <parameter>null_value_treatment</parameter> which must be one
        of <literal>'raise_exception'</literal>,
        <literal>'use_json_null'</literal>, <literal>'delete_key'</literal>, or
        <literal>'return_target'</literal>. The default is
        <literal>'use_json_null'</literal>.
       </para>
       <para>
        <literal>jsonb_set_lax('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', null)</literal>
        <returnvalue>[{"f1": null, "f2": null}, 2, null, 3]</returnvalue>
       </para>
       <para>
        <literal>jsonb_set_lax('[{"f1":99,"f2":null},2]', '{0,f3}', null, true, 'return_target')</literal>
        <returnvalue>[{"f1": 99, "f2": null}, 2]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_insert</primary>
        </indexterm>
        <function>jsonb_insert</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>text[]</type>, <parameter>new_value</parameter> <type>jsonb</type> <optional>, <parameter>insert_after</parameter> <type>boolean</type> </optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Returns <parameter>target</parameter>
        with <parameter>new_value</parameter> inserted.  If the item
        designated by the <parameter>path</parameter> is an array
        element, <parameter>new_value</parameter> will be inserted before
        that item if <parameter>insert_after</parameter> is false (which
        is the default), or after it
        if <parameter>insert_after</parameter> is true.  If the item
        designated by the <parameter>path</parameter> is an object
        field, <parameter>new_value</parameter> will be inserted only if
        the object does not already contain that key.
        All earlier steps in the path must exist, or
        the <parameter>target</parameter> is returned unchanged.
        As with the path oriented operators, negative integers that
        appear in the <parameter>path</parameter> count from the end
        of JSON arrays.
        If the last path step is an array index that is out of range, the new
        value is added at the beginning of the array if the index is negative,
        or at the end of the array if it is positive.
       </para>
       <para>
        <literal>jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"')</literal>
        <returnvalue>{"a": [0, "new_value", 1, 2]}</returnvalue>
       </para>
       <para>
        <literal>jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"', true)</literal>
        <returnvalue>{"a": [0, 1, "new_value", 2]}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_strip_nulls</primary>
        </indexterm>
        <function>json_strip_nulls</function> ( <parameter>target</parameter> <type>json</type> <optional>,<parameter>strip_in_arrays</parameter> <type>boolean</type> </optional> )
        <returnvalue>json</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_strip_nulls</primary>
        </indexterm>
        <function>jsonb_strip_nulls</function> ( <parameter>target</parameter> <type>jsonb</type> <optional>,<parameter>strip_in_arrays</parameter> <type>boolean</type> </optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Deletes all object fields that have null values from the given JSON
        value, recursively.
        If <parameter>strip_in_arrays</parameter> is true (the default is false),
        null array elements are also stripped.
        Otherwise they are not stripped. Bare null values are never stripped.
       </para>
       <para>
        <literal>json_strip_nulls('[{"f1":1, "f2":null}, 2, null, 3]')</literal>
        <returnvalue>[{"f1":1},2,null,3]</returnvalue>
       </para>
       <para>
        <literal>jsonb_strip_nulls('[1,2,null,3,4]', true)</literal>
        <returnvalue>[1,2,3,4]</returnvalue>
       </para>
       </entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_path_exists</primary>
        </indexterm>
        <function>jsonb_path_exists</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Checks whether the JSON path returns any item for the specified JSON
        value.
        (This is useful only with SQL-standard JSON path expressions, not
        <link linkend="functions-sqljson-check-expressions">predicate check
        expressions</link>, since those always return a value.)
        If the <parameter>vars</parameter> argument is specified, it must
        be a JSON object, and its fields provide named values to be
        substituted into the <type>jsonpath</type> expression.
        If the <parameter>silent</parameter> argument is specified and
        is <literal>true</literal>, the function suppresses the same errors
        as the <literal>@?</literal> and <literal>@@</literal> operators do.
       </para>
       <para>
        <literal>jsonb_path_exists('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min &amp;&amp; @ &lt;= $max)', '{"min":2, "max":4}')</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_path_match</primary>
        </indexterm>
        <function>jsonb_path_match</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Returns the SQL boolean result of a JSON path predicate check
        for the specified JSON value.
        (This is useful only
        with <link linkend="functions-sqljson-check-expressions">predicate
        check expressions</link>, not SQL-standard JSON path expressions,
        since it will either fail or return <literal>NULL</literal> if the
        path result is not a single boolean value.)
        The optional <parameter>vars</parameter>
        and <parameter>silent</parameter> arguments act the same as
        for <function>jsonb_path_exists</function>.
       </para>
       <para>
        <literal>jsonb_path_match('{"a":[1,2,3,4,5]}', 'exists($.a[*] ? (@ >= $min &amp;&amp; @ &lt;= $max))', '{"min":2, "max":4}')</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_path_query</primary>
        </indexterm>
        <function>jsonb_path_query</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>setof jsonb</returnvalue>
       </para>
       <para>
        Returns all JSON items returned by the JSON path for the specified
        JSON value.
        For SQL-standard JSON path expressions it returns the JSON
        values selected from <parameter>target</parameter>.
        For <link linkend="functions-sqljson-check-expressions">predicate
        check expressions</link> it returns the result of the predicate
        check: <literal>true</literal>, <literal>false</literal>,
        or <literal>null</literal>.
        The optional <parameter>vars</parameter>
        and <parameter>silent</parameter> arguments act the same as
        for <function>jsonb_path_exists</function>.
       </para>
       <para>
        <literal>SELECT * FROM jsonb_path_query('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min &amp;&amp; @ &lt;= $max)', '{"min":2, "max":4}')</literal>
        <returnvalue></returnvalue>
<programlisting>
 jsonb_path_query
------------------
 2
 3
 4
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_path_query_array</primary>
        </indexterm>
        <function>jsonb_path_query_array</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Returns all JSON items returned by the JSON path for the specified
        JSON value, as a JSON array.
        The parameters are the same as
        for <function>jsonb_path_query</function>.
       </para>
       <para>
        <literal>jsonb_path_query_array('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min &amp;&amp; @ &lt;= $max)', '{"min":2, "max":4}')</literal>
        <returnvalue>[2, 3, 4]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_path_query_first</primary>
        </indexterm>
        <function>jsonb_path_query_first</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        Returns the first JSON item returned by the JSON path for the
        specified JSON value, or <literal>NULL</literal> if there are no
        results.
        The parameters are the same as
        for <function>jsonb_path_query</function>.
       </para>
       <para>
        <literal>jsonb_path_query_first('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min &amp;&amp; @ &lt;= $max)', '{"min":2, "max":4}')</literal>
        <returnvalue>2</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_path_exists_tz</primary>
        </indexterm>
        <function>jsonb_path_exists_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>boolean</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_path_match_tz</primary>
        </indexterm>
        <function>jsonb_path_match_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>boolean</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_path_query_tz</primary>
        </indexterm>
        <function>jsonb_path_query_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>setof jsonb</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_path_query_array_tz</primary>
        </indexterm>
        <function>jsonb_path_query_array_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_path_query_first_tz</primary>
        </indexterm>
        <function>jsonb_path_query_first_tz</function> ( <parameter>target</parameter> <type>jsonb</type>, <parameter>path</parameter> <type>jsonpath</type> <optional>, <parameter>vars</parameter> <type>jsonb</type> <optional>, <parameter>silent</parameter> <type>boolean</type> </optional></optional> )
        <returnvalue>jsonb</returnvalue>
       </para>
       <para>
        These functions act like their counterparts described above without
        the <literal>_tz</literal> suffix, except that these functions support
        comparisons of date/time values that require timezone-aware
        conversions.  The example below requires interpretation of the
        date-only value <literal>2015-08-02</literal> as a timestamp with time
        zone, so the result depends on the current
        <xref linkend="guc-timezone"/> setting.  Due to this dependency, these
        functions are marked as stable, which means these functions cannot be
        used in indexes.  Their counterparts are immutable, and so can be used
        in indexes; but they will throw errors if asked to make such
        comparisons.
       </para>
       <para>
        <literal>jsonb_path_exists_tz('["2015-08-01 12:00:00-05"]', '$[*] ? (@.datetime() &lt; "2015-08-02".datetime())')</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>jsonb_pretty</primary>
        </indexterm>
        <function>jsonb_pretty</function> ( <type>jsonb</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Converts the given JSON value to pretty-printed, indented text.
       </para>
       <para>
        <literal>jsonb_pretty('[{"f1":1,"f2":null}, 2]')</literal>
        <returnvalue></returnvalue>
<programlisting>
[
    {
        "f1": 1,
        "f2": null
    },
    2
]
</programlisting>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <indexterm>
         <primary>json_typeof</primary>
        </indexterm>
        <function>json_typeof</function> ( <type>json</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para role="func_signature">
        <indexterm>
         <primary>jsonb_typeof</primary>
        </indexterm>
        <function>jsonb_typeof</function> ( <type>jsonb</type> )
        <returnvalue>text</returnvalue>
       </para>
       <para>
        Returns the type of the top-level JSON value as a text string.
        Possible types are
        <literal>object</literal>, <literal>array</literal>,
        <literal>string</literal>, <literal>number</literal>,
        <literal>boolean</literal>, and <literal>null</literal>.
        (The <literal>null</literal> result should not be confused
        with an SQL NULL; see the examples.)
       </para>
       <para>
        <literal>json_typeof('-123.4')</literal>
        <returnvalue>number</returnvalue>
       </para>
       <para>
        <literal>json_typeof('null'::json)</literal>
        <returnvalue>null</returnvalue>
       </para>
       <para>
        <literal>json_typeof(NULL::json) IS NULL</literal>
        <returnvalue>t</returnvalue>
       </para></entry>
      </row>
     </tbody>
    </tgroup>
   </table>
 </sect2>

 <sect2 id="functions-sqljson-path">
  <title>The SQL/JSON Path Language</title>

  <indexterm zone="functions-sqljson-path">
   <primary>SQL/JSON path language</primary>
  </indexterm>

  <para>
   SQL/JSON path expressions specify item(s) to be retrieved
   from a JSON value, similarly to XPath expressions used
   for access to XML content. In <productname>PostgreSQL</productname>,
   path expressions are implemented as the <type>jsonpath</type>
   data type and can use any elements described in
   <xref linkend="datatype-jsonpath"/>.
  </para>

  <para>
   JSON query functions and operators
   pass the provided path expression to the <firstterm>path engine</firstterm>
   for evaluation. If the expression matches the queried JSON data,
   the corresponding JSON item, or set of items, is returned.
   If there is no match, the result will be <literal>NULL</literal>,
   <literal>false</literal>, or an error, depending on the function.
   Path expressions are written in the SQL/JSON path language
   and can include arithmetic expressions and functions.
  </para>

  <para>
   A path expression consists of a sequence of elements allowed
   by the <type>jsonpath</type> data type.
   The path expression is normally evaluated from left to right, but
   you can use parentheses to change the order of operations.
   If the evaluation is successful, a sequence of JSON items is produced,
   and the evaluation result is returned to the JSON query function
   that completes the specified computation.
  </para>

  <para>
   To refer to the JSON value being queried (the
   <firstterm>context item</firstterm>), use the <literal>$</literal> variable
   in the path expression. The first element of a path must always
   be <literal>$</literal>. It can be followed by one or more
   <link linkend="type-jsonpath-accessors">accessor operators</link>,
   which go down the JSON structure level by level to retrieve sub-items
   of the context item. Each accessor operator acts on the
   result(s) of the previous evaluation step, producing zero, one, or more
   output items from each input item.
  </para>

  <para>
   For example, suppose you have some JSON data from a GPS tracker that you
   would like to parse, such as:
<programlisting>
SELECT '{
  "track": {
    "segments": [
      {
        "location":   [ 47.763, 13.4034 ],
        "start time": "2018-10-14 10:05:14",
        "HR": 73
      },
      {
        "location":   [ 47.706, 13.2635 ],
        "start time": "2018-10-14 10:39:21",
        "HR": 135
      }
    ]
  }
}' AS json \gset
</programlisting>
   (The above example can be copied-and-pasted
   into <application>psql</application> to set things up for the following
   examples.  Then <application>psql</application> will
   expand <literal>:'json'</literal> into a suitably-quoted string
   constant containing the JSON value.)
  </para>

  <para>
   To retrieve the available track segments, you need to use the
   <literal>.<replaceable>key</replaceable></literal> accessor
   operator to descend through surrounding JSON objects, for example:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments');</userinput>
                                                                         jsonb_path_query
-----------------------------------------------------------&zwsp;-----------------------------------------------------------&zwsp;---------------------------------------------
 [{"HR": 73, "location": [47.763, 13.4034], "start time": "2018-10-14 10:05:14"}, {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}]
</screen>
  </para>

  <para>
   To retrieve the contents of an array, you typically use the
   <literal>[*]</literal> operator.
   The following example will return the location coordinates for all
   the available track segments:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[*].location');</userinput>
 jsonb_path_query
-------------------
 [47.763, 13.4034]
 [47.706, 13.2635]
</screen>
   Here we started with the whole JSON input value (<literal>$</literal>),
   then the <literal>.track</literal> accessor selected the JSON object
   associated with the <literal>"track"</literal> object key, then
   the <literal>.segments</literal> accessor selected the JSON array
   associated with the <literal>"segments"</literal> key within that
   object, then the <literal>[*]</literal> accessor selected each element
   of that array (producing a series of items), then
   the <literal>.location</literal> accessor selected the JSON array
   associated with the <literal>"location"</literal> key within each of
   those objects.  In this example, each of those objects had
   a <literal>"location"</literal> key; but if any of them did not,
   the <literal>.location</literal> accessor would have simply produced no
   output for that input item.
  </para>

  <para>
   To return the coordinates of the first segment only, you can
   specify the corresponding subscript in the <literal>[]</literal>
   accessor operator. Recall that JSON array indexes are 0-relative:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[0].location');</userinput>
 jsonb_path_query
-------------------
 [47.763, 13.4034]
</screen>
  </para>

  <para>
   The result of each path evaluation step can be processed
   by one or more of the <type>jsonpath</type> operators and methods
   listed in <xref linkend="functions-sqljson-path-operators"/>.
   Each method name must be preceded by a dot. For example,
   you can get the size of an array:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments.size()');</userinput>
 jsonb_path_query
------------------
 2
</screen>
   More examples of using <type>jsonpath</type> operators
   and methods within path expressions appear below in
   <xref linkend="functions-sqljson-path-operators"/>.
  </para>

  <para>
   A path can also contain
   <firstterm>filter expressions</firstterm> that work similarly to the
   <literal>WHERE</literal> clause in SQL. A filter expression begins with
   a question mark and provides a condition in parentheses:

<synopsis>
? (<replaceable>condition</replaceable>)
</synopsis>
  </para>

  <para>
   Filter expressions must be written just after the path evaluation step
   to which they should apply. The result of that step is filtered to include
   only those items that satisfy the provided condition. SQL/JSON defines
   three-valued logic, so the condition can
   produce <literal>true</literal>, <literal>false</literal>,
   or <literal>unknown</literal>. The <literal>unknown</literal> value
   plays the same role as SQL <literal>NULL</literal> and can be tested
   for with the <literal>IS UNKNOWN</literal> predicate. Further path
   evaluation steps use only those items for which the filter expression
   returned <literal>true</literal>.
  </para>

  <para>
   The functions and operators that can be used in filter expressions are
   listed in <xref linkend="functions-sqljson-filter-ex-table"/>.  Within a
   filter expression, the <literal>@</literal> variable denotes the value
   being considered (i.e., one result of the preceding path step).  You can
   write accessor operators after <literal>@</literal> to retrieve component
   items.
  </para>

  <para>
   For example, suppose you would like to retrieve all heart rate values higher
   than 130. You can achieve this as follows:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[*].HR ? (@ &gt; 130)');</userinput>
 jsonb_path_query
------------------
 135
</screen>
  </para>

  <para>
   To get the start times of segments with such values, you have to
   filter out irrelevant segments before selecting the start times, so the
   filter expression is applied to the previous step, and the path used
   in the condition is different:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[*] ? (@.HR &gt; 130)."start time"');</userinput>
   jsonb_path_query
-----------------------
 "2018-10-14 10:39:21"
</screen>
  </para>

  <para>
   You can use several filter expressions in sequence, if required.
   The following example selects start times of all segments that
   contain locations with relevant coordinates and high heart rate values:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] &lt; 13.4) ? (@.HR &gt; 130)."start time"');</userinput>
   jsonb_path_query
-----------------------
 "2018-10-14 10:39:21"
</screen>
  </para>

  <para>
   Using filter expressions at different nesting levels is also allowed.
   The following example first filters all segments by location, and then
   returns high heart rate values for these segments, if available:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] &lt; 13.4).HR ? (@ &gt; 130)');</userinput>
 jsonb_path_query
------------------
 135
</screen>
  </para>

  <para>
   You can also nest filter expressions within each other.
   This example returns the size of the track if it contains any
   segments with high heart rate values, or an empty sequence otherwise:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track ? (exists(@.segments[*] ? (@.HR &gt; 130))).segments.size()');</userinput>
 jsonb_path_query
------------------
 2
</screen>
  </para>

  <sect3 id="functions-sqljson-deviations">
  <title>Deviations from the SQL Standard</title>
   <para>
    <productname>PostgreSQL</productname>'s implementation of the SQL/JSON path
    language has the following deviations from the SQL/JSON standard.
   </para>

   <sect4 id="functions-sqljson-check-expressions">
   <title>Boolean Predicate Check Expressions</title>
    <para>
     As an extension to the SQL standard,
     a <productname>PostgreSQL</productname> path expression can be a
     Boolean predicate, whereas the SQL standard allows predicates only within
     filters. While SQL-standard path expressions return the relevant
     element(s) of the queried JSON value, predicate check expressions
     return the single three-valued <type>jsonb</type> result of the
     predicate: <literal>true</literal>,
     <literal>false</literal>, or <literal>null</literal>.
     For example, we could write this SQL-standard filter expression:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments ?(@[*].HR &gt; 130)');</userinput>
                                jsonb_path_query
-----------------------------------------------------------&zwsp;----------------------
 {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}
</screen>
     The similar predicate check expression simply
     returns <literal>true</literal>, indicating that a match exists:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', '$.track.segments[*].HR &gt; 130');</userinput>
 jsonb_path_query
------------------
 true
</screen>
     </para>

     <note>
      <para>
       Predicate check expressions are required in the
       <literal>@@</literal> operator (and the
       <function>jsonb_path_match</function> function), and should not be used
       with the <literal>@?</literal> operator (or the
       <function>jsonb_path_exists</function> function).
      </para>
     </note>
    </sect4>

    <sect4 id="functions-sqljson-regular-expression-deviation">
    <title>Regular Expression Interpretation</title>
     <para>
      There are minor differences in the interpretation of regular
      expression patterns used in <literal>like_regex</literal> filters, as
      described in <xref linkend="jsonpath-regular-expressions"/>.
     </para>
    </sect4>
   </sect3>

   <sect3 id="functions-sqljson-strict-and-lax-modes">
   <title>Strict and Lax Modes</title>
    <para>
     When you query JSON data, the path expression may not match the
     actual JSON data structure. An attempt to access a non-existent
     member of an object or element of an array is defined as a
     structural error. SQL/JSON path expressions have two modes
     of handling structural errors:
    </para>

   <itemizedlist>
    <listitem>
     <para>
      lax (default) &mdash; the path engine implicitly adapts
      the queried data to the specified path.
      Any structural errors that cannot be fixed as described below
      are suppressed, producing no match.
     </para>
    </listitem>
    <listitem>
     <para>
      strict &mdash; if a structural error occurs, an error is raised.
     </para>
    </listitem>
   </itemizedlist>

   <para>
    Lax mode facilitates matching of a JSON document and path
    expression when the JSON data does not conform to the expected schema.
    If an operand does not match the requirements of a particular operation,
    it can be automatically wrapped as an SQL/JSON array, or unwrapped by
    converting its elements into an SQL/JSON sequence before performing
    the operation. Also, comparison operators automatically unwrap their
    operands in lax mode, so you can compare SQL/JSON arrays
    out-of-the-box. An array of size 1 is considered equal to its sole element.
    Automatic unwrapping is not performed when:
    <itemizedlist>
     <listitem>
      <para>
       The path expression contains <literal>type()</literal> or
       <literal>size()</literal> methods that return the type
       and the number of elements in the array, respectively.
      </para>
     </listitem>
     <listitem>
      <para>
       The queried JSON data contain nested arrays. In this case, only
       the outermost array is unwrapped, while all the inner arrays
       remain unchanged. Thus, implicit unwrapping can only go one
       level down within each path evaluation step.
      </para>
     </listitem>
    </itemizedlist>
   </para>

   <para>
    For example, when querying the GPS data listed above, you can
    abstract from the fact that it stores an array of segments
    when using lax mode:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'lax $.track.segments.location');</userinput>
 jsonb_path_query
-------------------
 [47.763, 13.4034]
 [47.706, 13.2635]
</screen>
   </para>

   <para>
    In strict mode, the specified path must exactly match the structure of
    the queried JSON document, so using this path
    expression will cause an error:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'strict $.track.segments.location');</userinput>
ERROR:  jsonpath member accessor can only be applied to an object
</screen>
    To get the same result as in lax mode, you have to explicitly unwrap the
    <literal>segments</literal> array:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'strict $.track.segments[*].location');</userinput>
 jsonb_path_query
-------------------
 [47.763, 13.4034]
 [47.706, 13.2635]
</screen>
   </para>

   <para>
    The unwrapping behavior of lax mode can lead to surprising results. For
    instance, the following query using the <literal>.**</literal> accessor
    selects every <literal>HR</literal> value twice:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'lax $.**.HR');</userinput>
 jsonb_path_query
------------------
 73
 135
 73
 135
</screen>
    This happens because the <literal>.**</literal> accessor selects both
    the <literal>segments</literal> array and each of its elements, while
    the <literal>.HR</literal> accessor automatically unwraps arrays when
    using lax mode. To avoid surprising results, we recommend using
    the <literal>.**</literal> accessor only in strict mode. The
    following query selects each <literal>HR</literal> value just once:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'strict $.**.HR');</userinput>
 jsonb_path_query
------------------
 73
 135
</screen>
   </para>

   <para>
    The unwrapping of arrays can also lead to unexpected results. Consider this
    example, which selects all the <literal>location</literal> arrays:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'lax $.track.segments[*].location');</userinput>
 jsonb_path_query
-------------------
 [47.763, 13.4034]
 [47.706, 13.2635]
(2 rows)
</screen>
    As expected it returns the full arrays. But applying a filter expression
    causes the arrays to be unwrapped to evaluate each item, returning only the
    items that match the expression:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'lax $.track.segments[*].location ?(@[*] &gt; 15)');</userinput>
 jsonb_path_query
------------------
 47.763
 47.706
(2 rows)
</screen>
    This despite the fact that the full arrays are selected by the path
    expression. Use strict mode to restore selecting the arrays:
<screen>
<prompt>=&gt;</prompt> <userinput>SELECT jsonb_path_query(:'json', 'strict $.track.segments[*].location ?(@[*] &gt; 15)');</userinput>
 jsonb_path_query
-------------------
 [47.763, 13.4034]
 [47.706, 13.2635]
(2 rows)
</screen>
   </para>
   </sect3>

   <sect3 id="functions-sqljson-path-operators">
   <title>SQL/JSON Path Operators and Methods</title>

   <para>
    <xref linkend="functions-sqljson-op-table"/> shows the operators and
    methods available in <type>jsonpath</type>.  Note that while the unary
    operators and methods can be applied to multiple values resulting from a
    preceding path step, the binary operators (addition etc.) can only be
    applied to single values.  In lax mode, methods applied to an array will be
    executed for each value in the array.  The exceptions are
    <literal>.type()</literal> and <literal>.size()</literal>, which apply to
    the array itself.
   </para>

   <table id="functions-sqljson-op-table">
    <title><type>jsonpath</type> Operators and Methods</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Operator/Method
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>+</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Addition
       </para>
       <para>
        <literal>jsonb_path_query('[2]', '$[0] + 3')</literal>
        <returnvalue>5</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>+</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Unary plus (no operation); unlike addition, this can iterate over
        multiple values
       </para>
       <para>
        <literal>jsonb_path_query_array('{"x": [2,3,4]}', '+ $.x')</literal>
        <returnvalue>[2, 3, 4]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>-</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Subtraction
       </para>
       <para>
        <literal>jsonb_path_query('[2]', '7 - $[0]')</literal>
        <returnvalue>5</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>-</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Negation; unlike subtraction, this can iterate over
        multiple values
       </para>
       <para>
        <literal>jsonb_path_query_array('{"x": [2,3,4]}', '- $.x')</literal>
        <returnvalue>[-2, -3, -4]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>*</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Multiplication
       </para>
       <para>
        <literal>jsonb_path_query('[4]', '2 * $[0]')</literal>
        <returnvalue>8</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>/</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Division
       </para>
       <para>
        <literal>jsonb_path_query('[8.5]', '$[0] / 2')</literal>
        <returnvalue>4.2500000000000000</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>%</literal> <replaceable>number</replaceable>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Modulo (remainder)
       </para>
       <para>
        <literal>jsonb_path_query('[32]', '$[0] % 10')</literal>
        <returnvalue>2</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>type()</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        Type of the JSON item (see <function>json_typeof</function>)
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, "2", {}]', '$[*].type()')</literal>
        <returnvalue>["number", "string", "object"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>size()</literal>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Size of the JSON item (number of array elements, or 1 if not an
        array)
       </para>
       <para>
        <literal>jsonb_path_query('{"m": [11, 15]}', '$.m.size()')</literal>
        <returnvalue>2</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>boolean()</literal>
        <returnvalue><replaceable>boolean</replaceable></returnvalue>
       </para>
       <para>
        Boolean value converted from a JSON boolean, number, or string
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, "yes", false]', '$[*].boolean()')</literal>
        <returnvalue>[true, true, false]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>string()</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String value converted from a JSON boolean, number, string, or
        datetime
       </para>
       <para>
        <literal>jsonb_path_query_array('[1.23, "xyz", false]', '$[*].string()')</literal>
        <returnvalue>["1.23", "xyz", "false"]</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp().string()')</literal>
        <returnvalue>"2023-08-15T12:34:56"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>double()</literal>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Approximate floating-point number converted from a JSON number or
        string
       </para>
       <para>
        <literal>jsonb_path_query('{"len": "1.9"}', '$.len.double() * 2')</literal>
        <returnvalue>3.8</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>.</literal> <literal>ceiling()</literal>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Nearest integer greater than or equal to the given number
       </para>
       <para>
        <literal>jsonb_path_query('{"h": 1.3}', '$.h.ceiling()')</literal>
        <returnvalue>2</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>.</literal> <literal>floor()</literal>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Nearest integer less than or equal to the given number
       </para>
       <para>
        <literal>jsonb_path_query('{"h": 1.7}', '$.h.floor()')</literal>
        <returnvalue>1</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>number</replaceable> <literal>.</literal> <literal>abs()</literal>
        <returnvalue><replaceable>number</replaceable></returnvalue>
       </para>
       <para>
        Absolute value of the given number
       </para>
       <para>
        <literal>jsonb_path_query('{"z": -0.3}', '$.z.abs()')</literal>
        <returnvalue>0.3</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>bigint()</literal>
        <returnvalue><replaceable>bigint</replaceable></returnvalue>
       </para>
       <para>
        Big integer value converted from a JSON number or string
       </para>
       <para>
        <literal>jsonb_path_query('{"len": "9876543219"}', '$.len.bigint()')</literal>
        <returnvalue>9876543219</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>decimal( [ <replaceable>precision</replaceable> [ , <replaceable>scale</replaceable> ] ] )</literal>
        <returnvalue><replaceable>decimal</replaceable></returnvalue>
       </para>
       <para>
        Rounded decimal value converted from a JSON number or string
        (<literal>precision</literal> and <literal>scale</literal> must be
        integer values)
       </para>
       <para>
        <literal>jsonb_path_query('1234.5678', '$.decimal(6, 2)')</literal>
        <returnvalue>1234.57</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>integer()</literal>
        <returnvalue><replaceable>integer</replaceable></returnvalue>
       </para>
       <para>
        Integer value converted from a JSON number or string
       </para>
       <para>
        <literal>jsonb_path_query('{"len": "12345"}', '$.len.integer()')</literal>
        <returnvalue>12345</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>.</literal> <literal>number()</literal>
        <returnvalue><replaceable>numeric</replaceable></returnvalue>
       </para>
       <para>
        Numeric value converted from a JSON number or string
       </para>
       <para>
        <literal>jsonb_path_query('{"len": "123.45"}', '$.len.number()')</literal>
        <returnvalue>123.45</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>datetime()</literal>
        <returnvalue><replaceable>datetime_type</replaceable></returnvalue>
        (see note)
       </para>
       <para>
        Date/time value converted from a string
       </para>
       <para>
        <literal>jsonb_path_query('["2015-8-1", "2015-08-12"]', '$[*] ? (@.datetime() &lt; "2015-08-2".datetime())')</literal>
        <returnvalue>"2015-8-1"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>datetime(<replaceable>template</replaceable>)</literal>
        <returnvalue><replaceable>datetime_type</replaceable></returnvalue>
        (see note)
       </para>
       <para>
        Date/time value converted from a string using the
        specified <function>to_timestamp</function> template
       </para>
       <para>
        <literal>jsonb_path_query_array('["12:30", "18:40"]', '$[*].datetime("HH24:MI")')</literal>
        <returnvalue>["12:30:00", "18:40:00"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>date()</literal>
        <returnvalue><replaceable>date</replaceable></returnvalue>
       </para>
       <para>
        Date value converted from a string
       </para>
       <para>
        <literal>jsonb_path_query('"2023-08-15"', '$.date()')</literal>
        <returnvalue>"2023-08-15"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>time()</literal>
        <returnvalue><replaceable>time without time zone</replaceable></returnvalue>
       </para>
       <para>
        Time without time zone value converted from a string
       </para>
       <para>
        <literal>jsonb_path_query('"12:34:56"', '$.time()')</literal>
        <returnvalue>"12:34:56"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>time(<replaceable>precision</replaceable>)</literal>
        <returnvalue><replaceable>time without time zone</replaceable></returnvalue>
       </para>
       <para>
        Time without time zone value converted from a string, with fractional
        seconds adjusted to the given precision
       </para>
       <para>
        <literal>jsonb_path_query('"12:34:56.789"', '$.time(2)')</literal>
        <returnvalue>"12:34:56.79"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>time_tz()</literal>
        <returnvalue><replaceable>time with time zone</replaceable></returnvalue>
       </para>
       <para>
        Time with time zone value converted from a string
       </para>
       <para>
        <literal>jsonb_path_query('"12:34:56 +05:30"', '$.time_tz()')</literal>
        <returnvalue>"12:34:56+05:30"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>time_tz(<replaceable>precision</replaceable>)</literal>
        <returnvalue><replaceable>time with time zone</replaceable></returnvalue>
       </para>
       <para>
        Time with time zone value converted from a string, with fractional
        seconds adjusted to the given precision
       </para>
       <para>
        <literal>jsonb_path_query('"12:34:56.789 +05:30"', '$.time_tz(2)')</literal>
        <returnvalue>"12:34:56.79+05:30"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>timestamp()</literal>
        <returnvalue><replaceable>timestamp without time zone</replaceable></returnvalue>
       </para>
       <para>
        Timestamp without time zone value converted from a string
       </para>
       <para>
        <literal>jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp()')</literal>
        <returnvalue>"2023-08-15T12:34:56"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>timestamp(<replaceable>precision</replaceable>)</literal>
        <returnvalue><replaceable>timestamp without time zone</replaceable></returnvalue>
       </para>
       <para>
        Timestamp without time zone value converted from a string, with
        fractional seconds adjusted to the given precision
       </para>
       <para>
        <literal>jsonb_path_query('"2023-08-15 12:34:56.789"', '$.timestamp(2)')</literal>
        <returnvalue>"2023-08-15T12:34:56.79"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>timestamp_tz()</literal>
        <returnvalue><replaceable>timestamp with time zone</replaceable></returnvalue>
       </para>
       <para>
        Timestamp with time zone value converted from a string
       </para>
       <para>
        <literal>jsonb_path_query('"2023-08-15 12:34:56 +05:30"', '$.timestamp_tz()')</literal>
        <returnvalue>"2023-08-15T12:34:56+05:30"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>timestamp_tz(<replaceable>precision</replaceable>)</literal>
        <returnvalue><replaceable>timestamp with time zone</replaceable></returnvalue>
       </para>
       <para>
        Timestamp with time zone value converted from a string, with fractional
        seconds adjusted to the given precision
       </para>
       <para>
        <literal>jsonb_path_query('"2023-08-15 12:34:56.789 +05:30"', '$.timestamp_tz(2)')</literal>
        <returnvalue>"2023-08-15T12:34:56.79+05:30"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>object</replaceable> <literal>.</literal> <literal>keyvalue()</literal>
        <returnvalue><replaceable>array</replaceable></returnvalue>
       </para>
       <para>
        The object's key-value pairs, represented as an array of objects
        containing three fields: <literal>"key"</literal>,
        <literal>"value"</literal>, and <literal>"id"</literal>;
        <literal>"id"</literal> is a unique identifier of the object the
        key-value pair belongs to
       </para>
       <para>
        <literal>jsonb_path_query_array('{"x": "20", "y": 32}', '$.keyvalue()')</literal>
        <returnvalue>[{"id": 0, "key": "x", "value": "20"}, {"id": 0, "key": "y", "value": 32}]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>lower()</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String converted to all lower case according to the rules of the database's locale.
       </para>
       <para>
        <literal>jsonb_path_query('"TOM"', '$.lower()')</literal>
        <returnvalue>"tom"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>upper()</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String converted to all upper case according to the rules of the database's locale.
       </para>
       <para>
        <literal>jsonb_path_query('"tom"', '$.upper()')</literal>
        <returnvalue>"TOM"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>initcap()</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String with the first letter of each word converted to upper case
        according to the rules of the database's locale. Words are sequences
        of alphanumeric characters separated by non-alphanumeric characters.
       </para>
       <para>
        <literal>jsonb_path_query('"hi THOMAS"', '$.initcap()')</literal>
        <returnvalue>"Hi Thomas"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>replace(<replaceable>from</replaceable>, <replaceable>to</replaceable>)</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String with all occurrences of substring from replaced with substring to.
       </para>
       <para>
        <literal>jsonb_path_query('"abcdefabcdef"', '$.replace("cd", "XX")')</literal>
        <returnvalue>"abXXefabXXef"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>split_part(<replaceable>delimiter</replaceable>, <replaceable>n</replaceable>)</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String split at occurrences of <replaceable>delimiter</replaceable>
        and returns the <replaceable>n</replaceable>'th field (counting from
        one) or, when <replaceable>n</replaceable> is negative, returns the
        |<replaceable>n</replaceable>|'th-from-last field.
       </para>
       <para>
        <literal>jsonb_path_query('"abc~@~def~@~ghi"', '$.split_part("~@~", 2)')</literal>
        <returnvalue>"def"</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query('"abc,def,ghi,jkl"', '$.split_part(",", 3)')</literal>
        <returnvalue>"ghi"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>ltrim([ <replaceable>characters</replaceable> ])</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String with the longest string containing only spaces or the
        characters in <replaceable>characters</replaceable> removed from the
        start of <replaceable>string</replaceable>
       </para>
       <para>
        <literal> jsonb_path_query('"  hello"', '$.ltrim()')</literal>
        <returnvalue>"hello"</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query('"zzzytest"', '$.ltrim("xyz")')</literal>
        <returnvalue>"test"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>rtrim([ <replaceable>characters</replaceable> ])</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String with the longest string containing only spaces or the
        characters in <replaceable>characters</replaceable> removed from the
        end of <replaceable>string</replaceable>
       </para>
       <para>
        <literal>jsonb_path_query('"hello  "', '$.rtrim()')</literal>
        <returnvalue>"hello"</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query('"testxxzx"', '$.rtrim("xyz")')</literal>
        <returnvalue>"test"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>.</literal> <literal>btrim([ <replaceable>characters</replaceable> ])</literal>
        <returnvalue><replaceable>string</replaceable></returnvalue>
       </para>
       <para>
        String with the longest string containing only spaces or the
        characters in <replaceable>characters</replaceable> removed from the
        start and end of <replaceable>string</replaceable>
       </para>
       <para>
        <literal>jsonb_path_query('"  hello  "', '$.btrim()')</literal>
        <returnvalue>"hello"</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query('"xyxtrimyyx"', '$.btrim("xyz")')</literal>
        <returnvalue>"trim"</returnvalue>
       </para></entry>
      </row>

     </tbody>
    </tgroup>
   </table>

    <note>
     <para>
      The result type of the <literal>datetime()</literal> and
      <literal>datetime(<replaceable>template</replaceable>)</literal>
      methods can be <type>date</type>, <type>timetz</type>, <type>time</type>,
      <type>timestamptz</type>, or <type>timestamp</type>.
      Both methods determine their result type dynamically.
     </para>
     <para>
      The <literal>datetime()</literal> method sequentially tries to
      match its input string to the ISO formats
      for <type>date</type>, <type>timetz</type>, <type>time</type>,
      <type>timestamptz</type>, and <type>timestamp</type>. It stops on
      the first matching format and emits the corresponding data type.
     </para>
     <para>
      The <literal>datetime(<replaceable>template</replaceable>)</literal>
      method determines the result type according to the fields used in the
      provided template string.
     </para>
     <para>
      The <literal>datetime()</literal> and
      <literal>datetime(<replaceable>template</replaceable>)</literal> methods
      use the same parsing rules as the <literal>to_timestamp</literal> SQL
      function does (see <xref linkend="functions-formatting"/>), with three
      exceptions.  First, these methods don't allow unmatched template
      patterns.  Second, only the following separators are allowed in the
      template string: minus sign, period, solidus (slash), comma, apostrophe,
      semicolon, colon and space.  Third, separators in the template string
      must exactly match the input string.
     </para>
     <para>
      If different date/time types need to be compared, an implicit cast is
      applied. A <type>date</type> value can be cast to <type>timestamp</type>
      or <type>timestamptz</type>, <type>timestamp</type> can be cast to
      <type>timestamptz</type>, and <type>time</type> to <type>timetz</type>.
      However, all but the first of these conversions depend on the current
      <xref linkend="guc-timezone"/> setting, and thus can only be performed
      within timezone-aware <type>jsonpath</type> functions.  Similarly, other
      date/time-related methods that convert strings to date/time types
      also do this casting, which may involve the current
      <xref linkend="guc-timezone"/> setting. Therefore, these conversions can
      also only be performed within timezone-aware <type>jsonpath</type>
      functions.
     </para>
    </note>

   <para>
    <xref linkend="functions-sqljson-filter-ex-table"/> shows the available
    filter expression elements.
   </para>

   <table id="functions-sqljson-filter-ex-table">
    <title><type>jsonpath</type> Filter Expression Elements</title>
    <tgroup cols="1">
     <thead>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        Predicate/Value
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
       </para></entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>==</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Equality comparison (this, and the other comparison operators, work on
        all JSON scalar values)
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == 1)')</literal>
        <returnvalue>[1, 1]</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == "a")')</literal>
        <returnvalue>["a"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>!=</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para role="func_signature">
        <replaceable>value</replaceable> <literal>&lt;&gt;</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Non-equality comparison
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, 2, 1, 3]', '$[*] ? (@ != 1)')</literal>
        <returnvalue>[2, 3]</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ &lt;&gt; "b")')</literal>
        <returnvalue>["a", "c"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>&lt;</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Less-than comparison
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ &lt; 2)')</literal>
        <returnvalue>[1]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>&lt;=</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Less-than-or-equal-to comparison
       </para>
       <para>
        <literal>jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ &lt;= "b")')</literal>
        <returnvalue>["a", "b"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>&gt;</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Greater-than comparison
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ &gt; 2)')</literal>
        <returnvalue>[3]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>value</replaceable> <literal>&gt;=</literal> <replaceable>value</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Greater-than-or-equal-to comparison
       </para>
       <para>
        <literal>jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ &gt;= 2)')</literal>
        <returnvalue>[2, 3]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>true</literal>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        JSON constant <literal>true</literal>
       </para>
       <para>
        <literal>jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == true)')</literal>
        <returnvalue>{"name": "Chris", "parent": true}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>false</literal>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        JSON constant <literal>false</literal>
       </para>
       <para>
        <literal>jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == false)')</literal>
        <returnvalue>{"name": "John", "parent": false}</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>null</literal>
        <returnvalue><replaceable>value</replaceable></returnvalue>
       </para>
       <para>
        JSON constant <literal>null</literal> (note that, unlike in SQL,
        comparison to <literal>null</literal> works normally)
       </para>
       <para>
        <literal>jsonb_path_query('[{"name": "Mary", "job": null}, {"name": "Michael", "job": "driver"}]', '$[*] ? (@.job == null) .name')</literal>
        <returnvalue>"Mary"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>boolean</replaceable> <literal>&amp;&amp;</literal> <replaceable>boolean</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Boolean AND
       </para>
       <para>
        <literal>jsonb_path_query('[1, 3, 7]', '$[*] ? (@ &gt; 1 &amp;&amp; @ &lt; 5)')</literal>
        <returnvalue>3</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>boolean</replaceable> <literal>||</literal> <replaceable>boolean</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Boolean OR
       </para>
       <para>
        <literal>jsonb_path_query('[1, 3, 7]', '$[*] ? (@ &lt; 1 || @ &gt; 5)')</literal>
        <returnvalue>7</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>!</literal> <replaceable>boolean</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Boolean NOT
       </para>
       <para>
        <literal>jsonb_path_query('[1, 3, 7]', '$[*] ? (!(@ &lt; 5))')</literal>
        <returnvalue>7</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>boolean</replaceable> <literal>is unknown</literal>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Tests whether a Boolean condition is <literal>unknown</literal>.
       </para>
       <para>
        <literal>jsonb_path_query('[-1, 2, 7, "foo"]', '$[*] ? ((@ > 0) is unknown)')</literal>
        <returnvalue>"foo"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>like_regex</literal> <replaceable>string</replaceable> <optional> <literal>flag</literal> <replaceable>string</replaceable> </optional>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Tests whether the first operand matches the regular expression
        given by the second operand, optionally with modifications
        described by a string of <literal>flag</literal> characters (see
        <xref linkend="jsonpath-regular-expressions"/>).
       </para>
       <para>
        <literal>jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c")')</literal>
        <returnvalue>["abc", "abdacb"]</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c" flag "i")')</literal>
        <returnvalue>["abc", "aBdC", "abdacb"]</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <replaceable>string</replaceable> <literal>starts with</literal> <replaceable>string</replaceable>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Tests whether the second operand is an initial substring of the first
        operand.
       </para>
       <para>
        <literal>jsonb_path_query('["John Smith", "Mary Stone", "Bob Johnson"]', '$[*] ? (@ starts with "John")')</literal>
        <returnvalue>"John Smith"</returnvalue>
       </para></entry>
      </row>

      <row>
       <entry role="func_table_entry"><para role="func_signature">
        <literal>exists</literal> <literal>(</literal> <replaceable>path_expression</replaceable> <literal>)</literal>
        <returnvalue>boolean</returnvalue>
       </para>
       <para>
        Tests whether a path expression matches at least one SQL/JSON item.
        Returns <literal>unknown</literal> if the path expression would result
        in an error; the second example uses this to avoid a no-such-key error
        in strict mode.
       </para>
       <para>
        <literal>jsonb_path_query('{"x": [1, 2], "y": [2, 4]}', 'strict $.* ? (exists (@ ? (@[*] &gt; 2)))')</literal>
        <returnvalue>[2, 4]</returnvalue>
       </para>
       <para>
        <literal>jsonb_path_query_array('{"value": 41}', 'strict $ ? (exists (@.name)) .name')</literal>
        <returnvalue>[]</returnvalue>
       </para></entry>
      </row>
     </tbody>
    </tgroup>
   </table>

   </sect3>

   <sect3 id="jsonpath-regular-expressions">
    <title>SQL/JSON Regular Expressions</title>

    <indexterm zone="jsonpath-regular-expressions">
     <primary><literal>LIKE_REGEX</literal></primary>
     <secondary>in SQL/JSON</secondary>
    </indexterm>

    <para>
     SQL/JSON path expressions allow matching text to a regular expression
     with the <literal>like_regex</literal> filter.  For example, the
     following SQL/JSON path query would case-insensitively match all
     strings in an array that start with an English vowel:
<programlisting>
$[*] ? (@ like_regex "^[aeiou]" flag "i")
</programlisting>
    </para>

    <para>
     The optional <literal>flag</literal> string may include one or more of
     the characters
     <literal>i</literal> for case-insensitive match,
     <literal>m</literal> to allow <literal>^</literal>
     and <literal>$</literal> to match at newlines,
     <literal>s</literal> to allow <literal>.</literal> to match a newline,
     and <literal>q</literal> to quote the whole pattern (reducing the
     behavior to a simple substring match).
    </para>

    <para>
     The SQL/JSON standard borrows its definition for regular expressions
     from the <literal>LIKE_REGEX</literal> operator, which in turn uses the
     XQuery standard.  PostgreSQL does not currently support the
     <literal>LIKE_REGEX</literal> operator.  Therefore,
     the <literal>like_regex</literal> filter is implemented using the
     POSIX regular expression engine described in
     <xref linkend="posix-syntax-details"/>.  This leads to various minor
     discrepancies from standard SQL/JSON behavior, which are cataloged in
     <xref linkend="posix-vs-xquery"/>.
     Note, however, that the flag-letter incompatibilities described there
     do not apply to SQL/JSON, as it translates the XQuery flag letters to
     match what the POSIX engine expects.
    </para>

    <para>
     Keep in mind that the pattern argument of <literal>like_regex</literal>
     is a JSON path string literal, written according to the rules given in
     <xref linkend="datatype-jsonpath"/>.  This means in particular that any
     backslashes you want to use in the regular expression must be doubled.
     For example, to match string values of the root document that contain
     only digits:
<programlisting>
$.* ? (@ like_regex "^\\d+$")
</programlisting>
    </para>
   </sect3>
  </sect2>

   <sect2 id="sqljson-query-functions">
    <title>SQL/JSON Query Functions</title>
  <para>
   SQL/JSON functions <literal>JSON_EXISTS()</literal>,
   <literal>JSON_QUERY()</literal>, and <literal>JSON_VALUE()</literal>
   described in <xref linkend="functions-sqljson-querying"/> can be used
   to query JSON documents.  Each of these functions apply a
   <replaceable>path_expression</replaceable> (an SQL/JSON path query) to a
   <replaceable>context_item</replaceable> (the document).  See
   <xref linkend="functions-sqljson-path"/> for more details on what
   the <replaceable>path_expression</replaceable> can contain. The
   <replaceable>path_expression</replaceable> can also reference variables,
   whose values are specified with their respective names in the
   <literal>PASSING</literal> clause that is supported by each function.
   <replaceable>context_item</replaceable> can be a <type>jsonb</type> value
   or a character string that can be successfully cast to <type>jsonb</type>.
  </para>

  <table id="functions-sqljson-querying">
   <title>SQL/JSON Query Functions</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="func_table_entry"><para role="func_signature">
        Function signature
       </para>
       <para>
        Description
       </para>
       <para>
        Example(s)
      </para></entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry role="func_table_entry"><para role="func_signature">
        <indexterm><primary>json_exists</primary></indexterm>
<synopsis>
<function>JSON_EXISTS</function> (
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable>
<optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional>
<optional>{ <literal>TRUE</literal> | <literal>FALSE</literal> |<literal> UNKNOWN</literal> | <literal>ERROR</literal> } <literal>ON ERROR</literal> </optional>) <returnvalue>boolean</returnvalue>
</synopsis>
       </para>
     <itemizedlist>
      <listitem>
       <para>
        Returns true if the SQL/JSON <replaceable>path_expression</replaceable>
        applied to the <replaceable>context_item</replaceable> yields any
        items, false otherwise.
       </para>
      </listitem>
      <listitem>
       <para>
        The <literal>ON ERROR</literal> clause specifies the behavior if
        an error occurs during <replaceable>path_expression</replaceable>
        evaluation.  Specifying <literal>ERROR</literal> will cause an error to
        be thrown with the appropriate message.  Other options include
        returning <type>boolean</type> values <literal>FALSE</literal> or
        <literal>TRUE</literal> or the value <literal>UNKNOWN</literal> which
        is actually an SQL NULL. The default when no <literal>ON ERROR</literal>
        clause is specified is to return the <type>boolean</type> value
        <literal>FALSE</literal>.
       </para>
      </listitem>
      </itemizedlist>
       <para>
        Examples:
       </para>
       <para>
        <literal>JSON_EXISTS(jsonb '{"key1": [1,2,3]}', 'strict $.key1[*] ? (@ > $x)' PASSING 2 AS x)</literal>
        <returnvalue>t</returnvalue>
       </para>
       <para>
        <literal>JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'lax $.a[5]' ERROR ON ERROR)</literal>
        <returnvalue>f</returnvalue>
       </para>
       <para>
        <literal>JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'strict $.a[5]' ERROR ON ERROR)</literal>
        <returnvalue></returnvalue>
<programlisting>
ERROR:  jsonpath array subscript is out of bounds
</programlisting>
      </para></entry>
     </row>
     <row>
      <entry role="func_table_entry"><para role="func_signature">
        <indexterm><primary>json_query</primary></indexterm>
<synopsis>
<function>JSON_QUERY</function> (
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable>
<optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional>
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> <optional> <literal>FORMAT JSON</literal> <optional> <literal>ENCODING UTF8</literal> </optional> </optional> </optional>
<optional> { <literal>WITHOUT</literal> | <literal>WITH</literal> { <literal>CONDITIONAL</literal> | <optional><literal>UNCONDITIONAL</literal></optional> } } <optional> <literal>ARRAY</literal> </optional> <literal>WRAPPER</literal> </optional>
<optional> { <literal>KEEP</literal> | <literal>OMIT</literal> } <literal>QUOTES</literal> <optional> <literal>ON SCALAR STRING</literal> </optional> </optional>
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>EMPTY</literal> { <optional> <literal>ARRAY</literal> </optional> | <literal>OBJECT</literal> } | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON EMPTY</literal> </optional>
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>EMPTY</literal> { <optional> <literal>ARRAY</literal> </optional> | <literal>OBJECT</literal> } | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON ERROR</literal> </optional>) <returnvalue>jsonb</returnvalue>
</synopsis>
      </para>
     <itemizedlist>
      <listitem>
       <para>
        Returns the result of applying the SQL/JSON
        <replaceable>path_expression</replaceable> to the
        <replaceable>context_item</replaceable>.
       </para>
      </listitem>
      <listitem>
       <para>
         By default, the result is returned as a value of type <type>jsonb</type>,
         though the <literal>RETURNING</literal> clause can be used to return
         as some other type to which it can be successfully coerced.
       </para>
      </listitem>
      <listitem>
       <para>
        If the path expression may return multiple values, it might be necessary
        to wrap those values using the <literal>WITH WRAPPER</literal> clause to
        make it a valid JSON string, because the default behavior is to not wrap
        them, as if <literal>WITHOUT WRAPPER</literal> were specified. The
        <literal>WITH WRAPPER</literal> clause is by default taken to mean
        <literal>WITH UNCONDITIONAL WRAPPER</literal>, which means that even a
        single result value will be wrapped. To apply the wrapper only when
        multiple values are present, specify <literal>WITH CONDITIONAL WRAPPER</literal>.
        Getting multiple values in result will be treated as an error if
        <literal>WITHOUT WRAPPER</literal> is specified.
       </para>
      </listitem>
      <listitem>
       <para>
        If the result is a scalar string, by default, the returned value will
        be surrounded by quotes, making it a valid JSON value.  It can be made
        explicit by specifying <literal>KEEP QUOTES</literal>.  Conversely,
        quotes can be omitted by specifying <literal>OMIT QUOTES</literal>.
        To ensure that the result is a valid JSON value, <literal>OMIT QUOTES</literal>
        cannot be specified when <literal>WITH WRAPPER</literal> is also
        specified.
       </para>
      </listitem>
      <listitem>
       <para>
        The <literal>ON EMPTY</literal> clause specifies the behavior if
        evaluating <replaceable>path_expression</replaceable> yields an empty
        set. The <literal>ON ERROR</literal> clause specifies the behavior
        if an error occurs when evaluating <replaceable>path_expression</replaceable>,
        when coercing the result value to the <literal>RETURNING</literal> type,
        or when evaluating the <literal>ON EMPTY</literal> expression if the
        <replaceable>path_expression</replaceable> evaluation returns an empty
        set.
       </para>
      </listitem>
      <listitem>
       <para>
        For both <literal>ON EMPTY</literal> and <literal>ON ERROR</literal>,
        specifying <literal>ERROR</literal> will cause an error to be thrown with
        the appropriate message. Other options include returning an SQL NULL, an
        empty array (<literal>EMPTY <optional>ARRAY</optional></literal>),
        an empty object (<literal>EMPTY OBJECT</literal>), or a user-specified
        expression (<literal>DEFAULT</literal> <replaceable>expression</replaceable>)
        that can be coerced to jsonb or the type specified in <literal>RETURNING</literal>.
        The default when <literal>ON EMPTY</literal> or <literal>ON ERROR</literal>
        is not specified is to return an SQL NULL value.
       </para>
      </listitem>
     </itemizedlist>
       <para>
        Examples:
       </para>
       <para>
        <literal>JSON_QUERY(jsonb '[1,[2,3],null]', 'lax $[*][$off]' PASSING 1 AS off WITH CONDITIONAL WRAPPER)</literal>
        <returnvalue>3</returnvalue>
       </para>
       <para>
        <literal>JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' OMIT QUOTES)</literal>
        <returnvalue>[1, 2]</returnvalue>
       </para>
       <para>
        <literal>JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' RETURNING int[] OMIT QUOTES ERROR ON ERROR)</literal>
        <returnvalue></returnvalue>
<programlisting>
ERROR:  malformed array literal: "[1, 2]"
DETAIL:  Missing "]" after array dimensions.
</programlisting>
       </para>
      </entry>
     </row>
     <row>
      <entry role="func_table_entry"><para role="func_signature">
        <indexterm><primary>json_value</primary></indexterm>
<synopsis>
<function>JSON_VALUE</function> (
<replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable>
<optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional>
<optional> <literal>RETURNING</literal> <replaceable>data_type</replaceable> </optional>
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON EMPTY</literal> </optional>
<optional> { <literal>ERROR</literal> | <literal>NULL</literal> | <literal>DEFAULT</literal> <replaceable>expression</replaceable> } <literal>ON ERROR</literal> </optional>) <returnvalue>text</returnvalue>
</synopsis>
       </para>
     <itemizedlist>
      <listitem>
       <para>
        Returns the result of applying the SQL/JSON
        <replaceable>path_expression</replaceable> to the
        <replaceable>context_item</replaceable>.
       </para>
      </listitem>
      <listitem>
       <para>
        Only use <function>JSON_VALUE()</function> if the extracted value is
        expected to be a single <acronym>SQL/JSON</acronym> scalar item;
        getting multiple values will be treated as an error. If you expect that
        extracted value might be an object or an array, use the
        <function>JSON_QUERY</function> function instead.
       </para>
      </listitem>
      <listitem>
       <para>
        By default, the result, which must be a single scalar value, is
        returned as a value of type <type>text</type>, though the
        <literal>RETURNING</literal> clause can be used to return as some
        other type to which it can be successfully coerced.
       </para>
      </listitem>
      <listitem>
       <para>
        The <literal>ON ERROR</literal> and <literal>ON EMPTY</literal>
        clauses have similar semantics as mentioned in the description of
        <function>JSON_QUERY</function>, except the set of values returned in
        lieu of throwing an error is different.
       </para>
      </listitem>
      <listitem>
       <para>
        Note that scalar strings returned by <function>JSON_VALUE</function>
        always have their quotes removed, equivalent to specifying
        <literal>OMIT QUOTES</literal> in <function>JSON_QUERY</function>.
       </para>
      </listitem>
     </itemizedlist>
       <para>
        Examples:
       </para>
       <para>
        <literal>JSON_VALUE(jsonb '"123.45"', '$' RETURNING float)</literal>
        <returnvalue>123.45</returnvalue>
       </para>
       <para>
        <literal>JSON_VALUE(jsonb '"03:04 2015-02-01"', '$.datetime("HH24:MI&nbsp;YYYY-MM-DD")' RETURNING date)</literal>
        <returnvalue>2015-02-01</returnvalue>
       </para>
       <para>
        <literal>JSON_VALUE(jsonb '[1,2]', 'strict $[$off]' PASSING 1 AS off)</literal>
        <returnvalue>2</returnvalue>
       </para>
       <para>
        <literal>JSON_VALUE(jsonb '[1,2]', 'strict $[*]' DEFAULT 9 ON ERROR)</literal>
        <returnvalue>9</returnvalue>
       </para>
      </entry>
     </row>
    </tbody>
   </tgroup>
  </table>
  <note>
   <para>
    The <replaceable>context_item</replaceable> expression is converted to
    <type>jsonb</type> by an implicit cast if the expression is not already of
    type <type>jsonb</type>. Note, however, that any parsing errors that occur
    during that conversion are thrown unconditionally, that is, are not
    handled according to the (specified or implicit) <literal>ON ERROR</literal>
    clause.
   </para>
  </note>
  <note>
   <para>
    <function>JSON_VALUE()</function> returns an SQL NULL if
    <replaceable>path_expression</replaceable> returns a JSON
    <literal>null</literal>, whereas <function>JSON_QUERY()</function> returns
    the JSON <literal>null</literal> as is.
   </para>
  </note>
  </sect2>

 <sect2 id="functions-sqljson-table">
  <title>JSON_TABLE</title>
  <indexterm>
   <primary>json_table</primary>
  </indexterm>

  <para>
   <function>JSON_TABLE</function> is an SQL/JSON function which
   queries <acronym>JSON</acronym> data
   and presents the results as a relational view, which can be accessed as a
   regular SQL table. You can use <function>JSON_TABLE</function> inside
   the <literal>FROM</literal> clause of a <literal>SELECT</literal>,
   <literal>UPDATE</literal>, or <literal>DELETE</literal> and as data source
   in a <literal>MERGE</literal> statement.
  </para>

  <para>
   Taking JSON data as input, <function>JSON_TABLE</function> uses a JSON path
   expression to extract a part of the provided data to use as a
   <firstterm>row pattern</firstterm> for the constructed view.  Each SQL/JSON
   value given by the row pattern serves as source for a separate row in the
   constructed view.
  </para>

  <para>
   To split the row pattern into columns, <function>JSON_TABLE</function>
   provides the <literal>COLUMNS</literal> clause that defines the
   schema of the created view. For each column, a separate JSON path expression
   can be specified to be evaluated against the row pattern to get an SQL/JSON
   value that will become the value for the specified column in a given output
   row.
  </para>

  <para>
   JSON data stored at a nested level of the row pattern can be extracted using
   the <literal>NESTED PATH</literal> clause.  Each
   <literal>NESTED PATH</literal> clause can be used to generate one or more
   columns using the data from a nested level of the row pattern.  Those
   columns can be specified using a <literal>COLUMNS</literal> clause that
   looks similar to the top-level COLUMNS clause.  Rows constructed from
   NESTED COLUMNS are called <firstterm>child rows</firstterm> and are joined
   against the row constructed from the columns specified in the parent
   <literal>COLUMNS</literal> clause to get the row in the final view.  Child
   columns themselves may contain a <literal>NESTED PATH</literal>
   specification thus allowing to extract data located at arbitrary nesting
   levels.  Columns produced by multiple <literal>NESTED PATH</literal>s at the
   same level are considered to be <firstterm>siblings</firstterm> of each
   other and their rows after joining with the parent row are combined using
   UNION.
  </para>

  <para>
   The rows produced by <function>JSON_TABLE</function> are laterally
   joined to the row that generated them, so you do not have to explicitly join
   the constructed view with the original table holding <acronym>JSON</acronym>
   data.
  </para>

  <para>
   The syntax is:
  </para>

<synopsis>
JSON_TABLE (
    <replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable> <optional> AS <replaceable>json_path_name</replaceable> </optional> <optional> PASSING { <replaceable>value</replaceable> AS <replaceable>varname</replaceable> } <optional>, ...</optional> </optional>
    COLUMNS ( <replaceable class="parameter">json_table_column</replaceable> <optional>, ...</optional> )
    <optional> { <literal>ERROR</literal> | <literal>EMPTY</literal> <optional>ARRAY</optional>} <literal>ON ERROR</literal> </optional>
)

<phrase>
where <replaceable class="parameter">json_table_column</replaceable> is:
</phrase>
  <replaceable>name</replaceable> FOR ORDINALITY
  | <replaceable>name</replaceable> <replaceable>type</replaceable>
        <optional> FORMAT JSON <optional>ENCODING <literal>UTF8</literal></optional></optional>
        <optional> PATH <replaceable>path_expression</replaceable> </optional>
        <optional> { WITHOUT | WITH { CONDITIONAL | <optional>UNCONDITIONAL</optional> } } <optional> ARRAY </optional> WRAPPER </optional>
        <optional> { KEEP | OMIT } QUOTES <optional> ON SCALAR STRING </optional> </optional>
        <optional> { ERROR | NULL | EMPTY { <optional>ARRAY</optional> | OBJECT } | DEFAULT <replaceable>expression</replaceable> } ON EMPTY </optional>
        <optional> { ERROR | NULL | EMPTY { <optional>ARRAY</optional> | OBJECT } | DEFAULT <replaceable>expression</replaceable> } ON ERROR </optional>
  | <replaceable>name</replaceable> <replaceable>type</replaceable> EXISTS <optional> PATH <replaceable>path_expression</replaceable> </optional>
        <optional> { ERROR | TRUE | FALSE | UNKNOWN } ON ERROR </optional>
  | NESTED <optional> PATH </optional> <replaceable>path_expression</replaceable> <optional> AS <replaceable>json_path_name</replaceable> </optional> COLUMNS ( <replaceable>json_table_column</replaceable> <optional>, ...</optional> )
</synopsis>

  <para>
   Each syntax element is described below in more detail.
  </para>

  <variablelist>
   <varlistentry>
    <term>
     <literal><replaceable>context_item</replaceable>, <replaceable>path_expression</replaceable> <optional> <literal>AS</literal> <replaceable>json_path_name</replaceable> </optional> <optional> <literal>PASSING</literal> { <replaceable>value</replaceable> <literal>AS</literal> <replaceable>varname</replaceable> } <optional>, ...</optional></optional></literal>
    </term>
    <listitem>
    <para>
     The <replaceable>context_item</replaceable> specifies the input document
     to query, the <replaceable>path_expression</replaceable> is an SQL/JSON
     path expression defining the query, and <replaceable>json_path_name</replaceable>
     is an optional name for the <replaceable>path_expression</replaceable>.
     The optional <literal>PASSING</literal> clause provides data values for
     the variables mentioned in the <replaceable>path_expression</replaceable>.
     The result of the input data evaluation using the aforementioned elements
     is called the <firstterm>row pattern</firstterm>, which is used as the
     source for row values in the constructed view.
    </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term>
     <literal>COLUMNS</literal> ( <replaceable>json_table_column</replaceable> <optional>, ...</optional> )
    </term>
    <listitem>

    <para>
     The <literal>COLUMNS</literal> clause defining the schema of the
     constructed view. In this clause, you can specify each column to be
     filled with an SQL/JSON value obtained by applying a JSON path expression
     against the row pattern.  <replaceable>json_table_column</replaceable> has
     the following variants:
    </para>

  <variablelist>
   <varlistentry>
    <term>
     <replaceable>name</replaceable> <literal>FOR ORDINALITY</literal>
    </term>
    <listitem>
    <para>
     Adds an ordinality column that provides sequential row numbering starting
     from 1.  Each <literal>NESTED PATH</literal> (see below) gets its own
     counter for any nested ordinality columns.
    </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term>
     <literal><replaceable>name</replaceable> <replaceable>type</replaceable>
          <optional><literal>FORMAT JSON</literal> <optional>ENCODING <literal>UTF8</literal></optional></optional>
          <optional> <literal>PATH</literal> <replaceable>path_expression</replaceable> </optional></literal>
    </term>
    <listitem>
    <para>
     Inserts an SQL/JSON value obtained by applying
     <replaceable>path_expression</replaceable> against the row pattern into
     the view's output row after coercing it to specified
     <replaceable>type</replaceable>.
    </para>
    <para>
     Specifying <literal>FORMAT JSON</literal> makes it explicit that you
     expect the value to be a valid <type>json</type> object.  It only
     makes sense to specify <literal>FORMAT JSON</literal> if
     <replaceable>type</replaceable> is one of <type>bpchar</type>,
     <type>bytea</type>, <type>character varying</type>, <type>name</type>,
     <type>json</type>, <type>jsonb</type>, <type>text</type>, or a domain over
     these types.
    </para>
    <para>
     Optionally, you can specify <literal>WRAPPER</literal> and
     <literal>QUOTES</literal> clauses to format the output. Note that
     specifying <literal>OMIT QUOTES</literal> overrides
     <literal>FORMAT JSON</literal> if also specified, because unquoted
     literals do not constitute valid <type>json</type> values.
    </para>
    <para>
     Optionally, you can use <literal>ON EMPTY</literal> and
     <literal>ON ERROR</literal> clauses to specify whether to throw the error
     or return the specified value when the result of JSON path evaluation is
     empty and when an error occurs during JSON path evaluation or when
     coercing the SQL/JSON value to the specified type, respectively.  The
     default for both is to return a <literal>NULL</literal> value.
    </para>
    <note>
     <para>
      This clause is internally turned into and has the same semantics as
      <function>JSON_VALUE</function> or <function>JSON_QUERY</function>.
      The latter if the specified type is not a scalar type or if either of
      <literal>FORMAT JSON</literal>, <literal>WRAPPER</literal>, or
      <literal>QUOTES</literal> clause is present.
     </para>
    </note>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term>
       <replaceable>name</replaceable> <replaceable>type</replaceable>
       <literal>EXISTS</literal> <optional> <literal>PATH</literal> <replaceable>path_expression</replaceable> </optional>
    </term>
    <listitem>
    <para>
     Inserts a boolean value obtained by applying
     <replaceable>path_expression</replaceable> against the row pattern
     into the view's output row after coercing it to specified
     <replaceable>type</replaceable>.
    </para>
    <para>
     The value corresponds to whether applying the <literal>PATH</literal>
     expression to the row pattern yields any values.
    </para>
    <para>
     The specified <replaceable>type</replaceable> should have a cast from the
     <type>boolean</type> type.
    </para>
    <para>
     Optionally, you can use <literal>ON ERROR</literal> to specify whether to
     throw the error or return the specified value when an error occurs during
     JSON path evaluation or when coercing SQL/JSON value to the specified
     type.  The default is to return a boolean value
     <literal>FALSE</literal>.
    </para>
    <note>
     <para>
      This clause is internally turned into and has the same semantics as
      <function>JSON_EXISTS</function>.
     </para>
    </note>
      </listitem>
   </varlistentry>

   <varlistentry>
    <term>
      <literal>NESTED <optional> PATH </optional></literal> <replaceable>path_expression</replaceable> <optional> <literal>AS</literal> <replaceable>json_path_name</replaceable> </optional>
          <literal>COLUMNS</literal> ( <replaceable>json_table_column</replaceable> <optional>, ...</optional> )
    </term>
    <listitem>

    <para>
     Extracts SQL/JSON values from nested levels of the row pattern,
     generates one or more columns as defined by the <literal>COLUMNS</literal>
     subclause, and inserts the extracted SQL/JSON values into those
     columns.  The <replaceable>json_table_column</replaceable>
     expression in the <literal>COLUMNS</literal> subclause uses the same
     syntax as in the parent <literal>COLUMNS</literal> clause.
    </para>

    <para>
     The <literal>NESTED PATH</literal> syntax is recursive,
     so you can go down multiple nested levels by specifying several
     <literal>NESTED PATH</literal> subclauses within each other.
     It allows to unnest the hierarchy of JSON objects and arrays
     in a single function invocation rather than chaining several
     <function>JSON_TABLE</function> expressions in an SQL statement.
    </para>
    </listitem>
   </varlistentry>
  </variablelist>

   <note>
     <para>
      In each variant of <replaceable>json_table_column</replaceable> described
      above, if the <literal>PATH</literal> clause is omitted, path expression
      <literal>$.<replaceable>name</replaceable></literal> is used, where
      <replaceable>name</replaceable> is the provided column name.
     </para>
    </note>

    </listitem>
   </varlistentry>

   <varlistentry>
    <term>
     <literal>AS</literal> <replaceable>json_path_name</replaceable>
    </term>
    <listitem>

    <para>
     The optional <replaceable>json_path_name</replaceable> serves as an
     identifier of the provided <replaceable>path_expression</replaceable>.
     The name must be unique and distinct from the column names.
    </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term>
     { <literal>ERROR</literal> | <literal>EMPTY</literal> } <literal>ON ERROR</literal>
    </term>
    <listitem>

    <para>
     The optional <literal>ON ERROR</literal> can be used to specify how to
     handle errors when evaluating the top-level
     <replaceable>path_expression</replaceable>.  Use <literal>ERROR</literal>
     if you want the errors to be thrown and <literal>EMPTY</literal> to
     return an empty table, that is, a table containing 0 rows.  Note that
     this clause does not affect the errors that occur when evaluating
     columns, for which the behavior depends on whether the
     <literal>ON ERROR</literal> clause is specified against a given column.
    </para>
    </listitem>
   </varlistentry>
  </variablelist>

  <para>Examples</para>

     <para>
      In the examples that follow, the following table containing JSON data
      will be used:

<programlisting>
CREATE TABLE my_films ( js jsonb );

INSERT INTO my_films VALUES (
'{ "favorites" : [
   { "kind" : "comedy", "films" : [
     { "title" : "Bananas",
       "director" : "Woody Allen"},
     { "title" : "The Dinner Game",
       "director" : "Francis Veber" } ] },
   { "kind" : "horror", "films" : [
     { "title" : "Psycho",
       "director" : "Alfred Hitchcock" } ] },
   { "kind" : "thriller", "films" : [
     { "title" : "Vertigo",
       "director" : "Alfred Hitchcock" } ] },
   { "kind" : "drama", "films" : [
     { "title" : "Yojimbo",
       "director" : "Akira Kurosawa" } ] }
  ] }');
</programlisting>

     </para>
     <para>
      The following query shows how to use <function>JSON_TABLE</function> to
      turn the JSON objects in the <structname>my_films</structname> table
      to a view containing columns for the keys <literal>kind</literal>,
      <literal>title</literal>, and <literal>director</literal> contained in
      the original JSON along with an ordinality column:

<programlisting>
SELECT jt.* FROM
 my_films,
 JSON_TABLE (js, '$.favorites[*]' COLUMNS (
   id FOR ORDINALITY,
   kind text PATH '$.kind',
   title text PATH '$.films[*].title' WITH WRAPPER,
   director text PATH '$.films[*].director' WITH WRAPPER)) AS jt;
</programlisting>

<screen>
 id |   kind   |             title              |             director
----+----------+--------------------------------+----------------------------------
  1 | comedy   | ["Bananas", "The Dinner Game"] | ["Woody Allen", "Francis Veber"]
  2 | horror   | ["Psycho"]                     | ["Alfred Hitchcock"]
  3 | thriller | ["Vertigo"]                    | ["Alfred Hitchcock"]
  4 | drama    | ["Yojimbo"]                    | ["Akira Kurosawa"]
(4 rows)
</screen>

     </para>
     <para>
      The following is a modified version of the above query to show the
      usage of <literal>PASSING</literal> arguments in the filter specified in
      the top-level JSON path expression and the various options for the
      individual columns:

<programlisting>
SELECT jt.* FROM
 my_films,
 JSON_TABLE (js, '$.favorites[*] ? (@.films[*].director == $filter)'
   PASSING 'Alfred Hitchcock' AS filter
     COLUMNS (
     id FOR ORDINALITY,
     kind text PATH '$.kind',
     title text FORMAT JSON PATH '$.films[*].title' OMIT QUOTES,
     director text PATH '$.films[*].director' KEEP QUOTES)) AS jt;
</programlisting>

<screen>
 id |   kind   |  title  |      director
----+----------+---------+--------------------
  1 | horror   | Psycho  | "Alfred Hitchcock"
  2 | thriller | Vertigo | "Alfred Hitchcock"
(2 rows)
</screen>

     </para>
     <para>
      The following is a modified version of the above query to show the usage
      of <literal>NESTED PATH</literal> for populating title and director
      columns, illustrating how they are joined to the parent columns id and
      kind:

<programlisting>
SELECT jt.* FROM
 my_films,
 JSON_TABLE ( js, '$.favorites[*] ? (@.films[*].director == $filter)'
   PASSING 'Alfred Hitchcock' AS filter
   COLUMNS (
    id FOR ORDINALITY,
    kind text PATH '$.kind',
    NESTED PATH '$.films[*]' COLUMNS (
      title text FORMAT JSON PATH '$.title' OMIT QUOTES,
      director text PATH '$.director' KEEP QUOTES))) AS jt;
</programlisting>

<screen>
 id |   kind   |  title  |      director
----+----------+---------+--------------------
  1 | horror   | Psycho  | "Alfred Hitchcock"
  2 | thriller | Vertigo | "Alfred Hitchcock"
(2 rows)
</screen>

     </para>

     <para>
      The following is the same query but without the filter in the root
      path:

<programlisting>
SELECT jt.* FROM
 my_films,
 JSON_TABLE ( js, '$.favorites[*]'
   COLUMNS (
    id FOR ORDINALITY,
    kind text PATH '$.kind',
    NESTED PATH '$.films[*]' COLUMNS (
      title text FORMAT JSON PATH '$.title' OMIT QUOTES,
      director text PATH '$.director' KEEP QUOTES))) AS jt;
</programlisting>

<screen>
 id |   kind   |      title      |      director
----+----------+-----------------+--------------------
  1 | comedy   | Bananas         | "Woody Allen"
  1 | comedy   | The Dinner Game | "Francis Veber"
  2 | horror   | Psycho          | "Alfred Hitchcock"
  3 | thriller | Vertigo         | "Alfred Hitchcock"
  4 | drama    | Yojimbo         | "Akira Kurosawa"
(5 rows)
</screen>

     </para>

     <para>
      The following shows another query using a different <type>JSON</type>
      object as input.  It shows the UNION "sibling join" between
      <literal>NESTED</literal> paths <literal>$.movies[*]</literal> and
      <literal>$.books[*]</literal> and also the usage of
      <literal>FOR ORDINALITY</literal> column at <literal>NESTED</literal>
      levels (columns <structfield>movie_id</structfield>, <structfield>book_id</structfield>,
      and <structfield>author_id</structfield>):

<programlisting>
SELECT * FROM JSON_TABLE (
'{"favorites":
    [{"movies":
      [{"name": "One", "director": "John Doe"},
       {"name": "Two", "director": "Don Joe"}],
     "books":
      [{"name": "Mystery", "authors": [{"name": "Brown Dan"}]},
       {"name": "Wonder", "authors": [{"name": "Jun Murakami"}, {"name":"Craig Doe"}]}]
}]}'::json, '$.favorites[*]'
COLUMNS (
  user_id FOR ORDINALITY,
  NESTED '$.movies[*]'
    COLUMNS (
    movie_id FOR ORDINALITY,
    mname text PATH '$.name',
    director text),
  NESTED '$.books[*]'
    COLUMNS (
      book_id FOR ORDINALITY,
      bname text PATH '$.name',
      NESTED '$.authors[*]'
        COLUMNS (
          author_id FOR ORDINALITY,
          author_name text PATH '$.name'))));
</programlisting>

<screen>
 user_id | movie_id | mname | director | book_id |  bname  | author_id | author_name
---------+----------+-------+----------+---------+---------+-----------+--------------
       1 |        1 | One   | John Doe |         |         |           |
       1 |        2 | Two   | Don Joe  |         |         |           |
       1 |          |       |          |       1 | Mystery |         1 | Brown Dan
       1 |          |       |          |       2 | Wonder  |         1 | Jun Murakami
       1 |          |       |          |       2 | Wonder  |         2 | Craig Doe
(5 rows)
</screen>

     </para>
  </sect2>
 </sect1>