ClickHouse

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#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionsVisitParam.h>
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#include <Functions/FunctionsStringSearch.h>
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namespace DB
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{
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struct ExtractBool
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{
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    using ResultType = UInt8;
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    static UInt8 extract(const UInt8 * begin, const UInt8 * end)
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    {
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        return begin + 4 <= end && 0 == strncmp(reinterpret_cast<const char *>(begin), "true", 4);
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    }
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};
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struct NameSimpleJSONExtractBool { static constexpr auto name = "simpleJSONExtractBool"; };
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using FunctionSimpleJSONExtractBool = FunctionsStringSearch<ExtractParamImpl<NameSimpleJSONExtractBool, ExtractBool>>;
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REGISTER_FUNCTION(VisitParamExtractBool)
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{
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    factory.registerFunction<FunctionSimpleJSONExtractBool>(FunctionDocumentation{
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        .description = "Parses a true/false value from the value of the field named field_name. The result is UInt8.",
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        .syntax = "simpleJSONExtractBool(json, field_name)",
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        .arguments
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        = {{"json", "The JSON in which the field is searched for. String."},
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           {"field_name", "The name of the field to search for. String literal."}},
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        .returned_value
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        = R"(It returns 1 if the value of the field is true, 0 otherwise. This means this function will return 0 including (and not only) in the following cases:
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 - If the field doesn't exists.
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 - If the field contains true as a string, e.g.: {"field":"true"}.
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 - If the field contains 1 as a numerical value.)",
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        .examples
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        = {{.name = "simple",
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            .query = R"(CREATE TABLE jsons
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(
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    json String
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)
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ENGINE = Memory;
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INSERT INTO jsons VALUES ('{"foo":false,"bar":true}');
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INSERT INTO jsons VALUES ('{"foo":"true","qux":1}');
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SELECT simpleJSONExtractBool(json, 'bar') FROM jsons ORDER BY json;
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SELECT simpleJSONExtractBool(json, 'foo') FROM jsons ORDER BY json;)",
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            .result = R"(0
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1
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0
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0)"}},
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        .categories{"JSON"}});
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    factory.registerAlias("visitParamExtractBool", "simpleJSONExtractBool");
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}
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}
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