</note>
<note>
- <para>
- While the examples for the functions
- <function>json_populate_record</function>,
- <function>json_populate_recordset</function>,
- <function>json_to_record</function> and
- <function>json_to_recordset</function> use constants, the typical use
- would be to reference a table in the <literal>FROM</literal> clause
- and use one of its <type>json</type> or <type>jsonb</type> columns
- as an argument to the function. Extracted key values can then be
- referenced in other parts of the query, like <literal>WHERE</literal>
- clauses and target lists. Extracting multiple values in this
- way can improve performance over extracting them separately with
- per-key operators.
- </para>
+ <para>
+ The functions
+ <function>json[b]_populate_record</function>,
+ <function>json[b]_populate_recordset</function>,
+ <function>json[b]_to_record</function> and
+ <function>json[b]_to_recordset</function>
+ operate on a JSON object, or array of objects, and extract the values
+ associated with keys whose names match column names of the output row
+ type.
+ Object fields that do not correspond to any output column name are
+ ignored, and output columns that do not match any object field will be
+ filled with nulls.
+ 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 a 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 literal, 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>
- JSON keys are matched to identical column names in the target
- row type. JSON type coercion for these functions is <quote>best
- effort</quote> and may not result in desired values for some types.
- JSON fields that do not appear in the target row type will be
- omitted from the output, and target columns that do not match any
- JSON field will simply be NULL.
- </para>
+ <para>
+ While the examples for these functions use constants, the typical use
+ would be to reference a table in the <literal>FROM</literal> clause
+ and use one of its <type>json</type> or <type>jsonb</type> columns
+ as an argument to the function. Extracted key values can then be
+ referenced in other parts of the query, like <literal>WHERE</literal>
+ clauses and target lists. Extracting multiple values in this
+ way can improve performance over extracting them separately with
+ per-key operators.
+ </para>
</note>
<note>
json = jsv->val.json.str;
Assert(json);
-
- /* already done the hard work in the json case */
- if ((typid == JSONOID || typid == JSONBOID) &&
- jsv->val.json.type == JSON_TOKEN_STRING)
- {
- /*
- * Add quotes around string value (should be already escaped) if
- * converting to json/jsonb.
- */
-
- if (len < 0)
- len = strlen(json);
-
- str = palloc(len + sizeof(char) * 3);
- str[0] = '"';
- memcpy(&str[1], json, len);
- str[len + 1] = '"';
- str[len + 2] = '\0';
- }
- else if (len >= 0)
+ if (len >= 0)
{
/* Need to copy non-null-terminated string */
str = palloc(len + 1 * sizeof(char));
str[len] = '\0';
}
else
- str = json; /* null-terminated string */
+ str = json; /* string is already null-terminated */
+
+ /* If converting to json/jsonb, make string into valid JSON literal */
+ if ((typid == JSONOID || typid == JSONBOID) &&
+ jsv->val.json.type == JSON_TOKEN_STRING)
+ {
+ StringInfoData buf;
+
+ initStringInfo(&buf);
+ escape_json(&buf, str);
+ /* free temporary buffer */
+ if (str != json)
+ pfree(str);
+ str = buf.data;
+ }
}
else
{
select * from json_to_record('{"ia2": [[1, 2], [3, 4]]}') as x(ia2 int4[][]);
select * from json_to_record('{"ia2": [[[1], [2], [3]]]}') as x(ia2 int4[][]);
+select * from json_to_record('{"out": {"key": 1}}') as x(out json);
+select * from json_to_record('{"out": [{"key": 1}]}') as x(out json);
+select * from json_to_record('{"out": "{\"key\": 1}"}') as x(out json);
+select * from json_to_record('{"out": {"key": 1}}') as x(out jsonb);
+select * from json_to_record('{"out": [{"key": 1}]}') as x(out jsonb);
+select * from json_to_record('{"out": "{\"key\": 1}"}') as x(out jsonb);
+
-- json_strip_nulls
select json_strip_nulls(null);
select * from jsonb_to_record('{"ia2": [[1, 2], [3, 4]]}') as x(ia2 int4[][]);
select * from jsonb_to_record('{"ia2": [[[1], [2], [3]]]}') as x(ia2 int4[][]);
+select * from jsonb_to_record('{"out": {"key": 1}}') as x(out json);
+select * from jsonb_to_record('{"out": [{"key": 1}]}') as x(out json);
+select * from jsonb_to_record('{"out": "{\"key\": 1}"}') as x(out json);
+select * from jsonb_to_record('{"out": {"key": 1}}') as x(out jsonb);
+select * from jsonb_to_record('{"out": [{"key": 1}]}') as x(out jsonb);
+select * from jsonb_to_record('{"out": "{\"key\": 1}"}') as x(out jsonb);
+
-- test type info caching in jsonb_populate_record()
CREATE TEMP TABLE jsbpoptest (js jsonb);
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