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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>41.8. Transaction Management</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="plpgsql-cursors.html" title="41.7. Cursors" /><link rel="next" href="plpgsql-errors-and-messages.html" title="41.9. Errors and Messages" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">41.8. Transaction Management</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql-cursors.html" title="41.7. Cursors">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 41. PL/pgSQL — SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 41. <span class="application">PL/pgSQL</span> — <acronym class="acronym">SQL</acronym> Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 18.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="plpgsql-errors-and-messages.html" title="41.9. Errors and Messages">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLPGSQL-TRANSACTIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">41.8. Transaction Management <a href="#PLPGSQL-TRANSACTIONS" class="id_link">#</a></h2></div></div></div><p>
    In procedures invoked by the <code class="command">CALL</code> command
    as well as in anonymous code blocks (<code class="command">DO</code> command),
    it is possible to end transactions using the
    commands <code class="command">COMMIT</code> and <code class="command">ROLLBACK</code>.  A new
    transaction is started automatically after a transaction is ended using
    these commands, so there is no separate <code class="command">START
    TRANSACTION</code> command.  (Note that <code class="command">BEGIN</code> and
    <code class="command">END</code> have different meanings in PL/pgSQL.)
   </p><p>
    Here is a simple example:
</p><pre class="programlisting">
CREATE PROCEDURE transaction_test1()
LANGUAGE plpgsql
AS $$
BEGIN
    FOR i IN 0..9 LOOP
        INSERT INTO test1 (a) VALUES (i);
        IF i % 2 = 0 THEN
            COMMIT;
        ELSE
            ROLLBACK;
        END IF;
    END LOOP;
END;
$$;

CALL transaction_test1();
</pre><p>
   </p><a id="id-1.8.8.10.4" class="indexterm"></a><p id="PLPGSQL-TRANSACTION-CHAIN">
    A new transaction starts out with default transaction characteristics such
    as transaction isolation level.  In cases where transactions are committed
    in a loop, it might be desirable to start new transactions automatically
    with the same characteristics as the previous one.  The commands
    <code class="command">COMMIT AND CHAIN</code> and <code class="command">ROLLBACK AND
    CHAIN</code> accomplish this.
   </p><p>
    Transaction control is only possible in <code class="command">CALL</code> or
    <code class="command">DO</code> invocations from the top level or nested
    <code class="command">CALL</code> or <code class="command">DO</code> invocations without any
    other intervening command.  For example, if the call stack is
    <code class="command">CALL proc1()</code> → <code class="command">CALL proc2()</code>
    → <code class="command">CALL proc3()</code>, then the second and third
    procedures can perform transaction control actions.  But if the call stack
    is <code class="command">CALL proc1()</code> → <code class="command">SELECT
    func2()</code> → <code class="command">CALL proc3()</code>, then the last
    procedure cannot do transaction control, because of the
    <code class="command">SELECT</code> in between.
   </p><p>
    <span class="application">PL/pgSQL</span> does not support savepoints
    (<code class="command">SAVEPOINT</code>/<code class="command">ROLLBACK TO
    SAVEPOINT</code>/<code class="command">RELEASE SAVEPOINT</code> commands).
    Typical usage patterns for savepoints can be replaced by blocks with
    exception handlers (see <a class="xref" href="plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING" title="41.6.8. Trapping Errors">Section 41.6.8</a>).
    Under the hood, a block with exception handlers forms a
    subtransaction, which means that transactions cannot be ended inside
    such a block.
   </p><p>
    Special considerations apply to cursor loops.  Consider this example:
</p><pre class="programlisting">
CREATE PROCEDURE transaction_test2()
LANGUAGE plpgsql
AS $$
DECLARE
    r RECORD;
BEGIN
    FOR r IN SELECT * FROM test2 ORDER BY x LOOP
        INSERT INTO test1 (a) VALUES (r.x);
        COMMIT;
    END LOOP;
END;
$$;

CALL transaction_test2();
</pre><p>
    Normally, cursors are automatically closed at transaction commit.
    However, a cursor created as part of a loop like this is automatically
    converted to a holdable cursor by the first <code class="command">COMMIT</code> or
    <code class="command">ROLLBACK</code>.  That means that the cursor is fully
    evaluated at the first <code class="command">COMMIT</code> or
    <code class="command">ROLLBACK</code> rather than row by row.  The cursor is still
    removed automatically after the loop, so this is mostly invisible to the
    user.  But one must keep in mind that any table or row locks taken by
    the cursor's query will no longer be held after the
    first <code class="command">COMMIT</code> or
    <code class="command">ROLLBACK</code>.
   </p><p>
    Transaction commands are not allowed in cursor loops driven by commands
    that are not read-only (for example <code class="command">UPDATE
    ... RETURNING</code>).
   </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plpgsql-cursors.html" title="41.7. Cursors">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html" title="Chapter 41. PL/pgSQL — SQL Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpgsql-errors-and-messages.html" title="41.9. Errors and Messages">Next</a></td></tr><tr><td width="40%" align="left" valign="top">41.7. Cursors </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 41.9. Errors and Messages</td></tr></table></div></body></html>