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diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 030ea8affdf..8ecc02f2b90 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -15488,6 +15488,11 @@ table2-mapping the SQL/JSON path language </para> </listitem> + <listitem> + <para> + the SQL/JSON query functions + </para> + </listitem> </itemizedlist> </para> @@ -18616,6 +18621,211 @@ $.* ? (@ like_regex "^\\d+$") </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> (the query) to a + <replaceable>context_item</replaceable> (the document); see + <xref linkend="functions-sqljson-path"/> for more details on what + <replaceable>path_expression</replaceable> can contain. + </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> + <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>) + </para> + <para> + Returns true if the SQL/JSON <replaceable>path_expression</replaceable> + applied to the <replaceable>context_item</replaceable> using the + <literal>PASSING</literal> <replaceable>value</replaceable>s yields any + items. + </para> + <para> + The <literal>ON ERROR</literal> clause specifies the behavior if + an error occurs; the default is to return the <type>boolean</type> + <literal>FALSE</literal> value. Note that if the + <replaceable>path_expression</replaceable> is <literal>strict</literal> + and <literal>ON ERROR</literal> behavior is <literal>ERROR</literal>, + an error is generated if it yields no items. + </para> + <para> + Examples: + </para> + <para> + <literal>select json_exists(jsonb '{"key1": [1,2,3]}', 'strict $.key1[*] ? (@ > 2)')</literal> + <returnvalue>t</returnvalue> + </para> + <para> + <literal>select json_exists(jsonb '{"a": [1,2,3]}', 'lax $.a[5]' ERROR ON ERROR)</literal> + <returnvalue>f</returnvalue> + </para> + <para> + <literal>select 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> + <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>) + </para> + <para> + Returns the result of applying the SQL/JSON + <replaceable>path_expression</replaceable> to the + <replaceable>context_item</replaceable> using the + <literal>PASSING</literal> <replaceable>value</replaceable>s. + </para> + <para> + If the path expression returns multiple SQL/JSON items, it might be + necessary to wrap the result using the <literal>WITH WRAPPER</literal> + clause to make it a valid JSON string. If the wrapper is + <literal>UNCONDITIONAL</literal>, an array wrapper will always be + applied, even if the returned value is already a single JSON object + or an array. If it is <literal>CONDITIONAL</literal>, it will not be + applied to a single JSON object or an array. + <literal>UNCONDITIONAL</literal> is the default. + </para> + <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>. + Note that <literal>OMIT QUOTES</literal> cannot be specified when + <literal>WITH WRAPPER</literal> is also specified. + </para> + <para> + The <literal>RETURNING</literal> clause can be used to specify the + <replaceable>data_type</replaceable> of the result value. By default, + the returned value will be of type <type>jsonb</type>. + </para> + <para> + The <literal>ON EMPTY</literal> clause specifies the behavior if + evaluating <replaceable>path_expression</replaceable> yields no value + at all. The default when <literal>ON EMPTY</literal> is not specified + is to return a null value. + </para> + <para> + The <literal>ON ERROR</literal> clause specifies the + behavior if an error occurs when evaluating + <replaceable>path_expression</replaceable>, including the operation to + coerce the result value to the output type, or during the execution of + <literal>ON EMPTY</literal> behavior (that is caused by empty result + of <replaceable>path_expression</replaceable> evaluation). The default + when <literal>ON ERROR</literal> is not specified is to return a null + value. + </para> + <para> + Examples: + </para> + <para> + <literal>select json_query(jsonb '[1,[2,3],null]', 'lax $[*][1]' WITH CONDITIONAL WRAPPER)</literal> + <returnvalue>[3]</returnvalue> + </para> + <para> + <literal>select json_query(jsonb '{"a": "[1, 2]"}', 'lax $.a' OMIT QUOTES);</literal> + <returnvalue>[1, 2]</returnvalue> + </para> + <para> + <literal>select 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> + <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>) + </para> + <para> + Returns the result of applying the SQL/JSON + <replaceable>path_expression</replaceable> to the + <replaceable>context_item</replaceable> using the + <literal>PASSING</literal> <replaceable>value</replaceable>s. + </para> + <para> + The extracted value must be a single <acronym>SQL/JSON</acronym> + scalar item; an error is thrown if that's not the case. If you expect + that extracted value might be an object or an array, use the + <function>json_query</function> function instead. + </para> + <para> + The <literal>RETURNING</literal> clause can be used to specify the + <replaceable>data_type</replaceable> of the result value. By default, + the returned value will be of type <type>text</type>. + </para> + <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>. + </para> + <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> + <para> + Examples: + </para> + <para> + <literal>select json_value(jsonb '"123.45"', '$' RETURNING float)</literal> + <returnvalue>123.45</returnvalue> + </para> + <para> + <literal>select json_value(jsonb '"03:04 2015-02-01"', '$.datetime("HH24:MI YYYY-MM-DD")' RETURNING date)</literal> + <returnvalue>2015-02-01</returnvalue> + </para> + <para> + <literal>select json_value(jsonb '[1,2]', 'strict $[*]' DEFAULT 9 ON ERROR)</literal> + <returnvalue>9</returnvalue> + </para></entry> + </row> + </tbody> + </tgroup> + </table> + </sect2> </sect1> <sect1 id="functions-sequence"> |