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New json functions.

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json_build_array() and json_build_object allow for the construction of
arbitrarily complex json trees. json_object() turns a one or two
dimensional array, or two separate arrays, into a json_object of
name/value pairs, similarly to the hstore() function.
json_object_agg() aggregates its two arguments into a single json object
as name value pairs.

Catalog version bumped.

Andrew Dunstan, reviewed by Marko Tiikkaja.
This commit is contained in:
Andrew Dunstan
2014-01-28 17:48:21 -05:00
parent 9132b189bf
commit 105639900b
10 changed files with 1221 additions and 71 deletions
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158
doc/src/sgml/func.sgml
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@ -10300,6 +10300,137 @@ table2-mapping
<entry><literal>json_typeof('-123.4')</literal></entry>
<entry><literal>number</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_build_array</primary>
</indexterm>
<literal>json_build_array(VARIADIC "any")</literal>
</entry>
<entry><type>json</type></entry>
<entry>
Builds a heterogeneously typed json array out of a variadic argument list.
</entry>
<entry><literal>SELECT json_build_array(1,2,'3',4,5);</literal></entry>
<entry>
<programlisting>
json_build_array
-------------------
[1, 2, "3", 4, 5]
</programlisting>
</entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_build_object</primary>
</indexterm>
<literal>json_build_object(VARIADIC "any")</literal>
</entry>
<entry><type>json</type></entry>
<entry>
Builds a JSON array out of a variadic agument list. By convention, the object is
constructed out of alternating name/value arguments.
</entry>
<entry><literal>SELECT json_build_object('foo',1,'bar',2);</literal></entry>
<entry>
<programlisting>
json_build_object
------------------------
{"foo" : 1, "bar" : 2}
</programlisting>
</entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_object</primary>
</indexterm>
<literal>json_object(text[])</literal>
</entry>
<entry><type>json</type></entry>
<entry>
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 name/value pairs, or two dimensions
such that each inner array has exactly two elements, which
are taken as a name/value pair.
</entry>
<entry><literal>select * from json_object('{a, 1, b, "def", c, 3.5}') or <literal>select * from json_object('{{a, 1},{b, "def"},{c, 3.5}}')</literal></literal></entry>
<entry>
<programlisting>
json_object
---------------------------------------
{"a" : "1", "b" : "def", "c" : "3.5"}
</programlisting>
</entry>
</row>
<row>
<entry>
<literal>json_object(keys text[], values text[])</literal>
</entry>
<entry><type>json</type></entry>
<entry>
The two argument form of JSON object takes keys and values pairwise from two separate
arrays. In all other respects it is identical to the one argument form.
</entry>
<entry><literal>select * from json_object('{a, b}', '{1,2}');</literal></entry>
<entry>
<programlisting>
json_object
------------------------
{"a" : "1", "b" : "2"}
</programlisting>
</entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_to_record</primary>
</indexterm>
<literal>json_to_record(json, nested_as_text bool)</literal>
</entry>
<entry><type>record</type></entry>
<entry>
json_to_record returns an arbitrary record from a JSON object. As with all functions
returning 'record', the caller must explicitly define the structure of the record
when making the call. The input JSON must be an object, not a scalar or an array.
If nested_as_text is true, the function coerces nested complex elements to text.
Also, see notes below on columns and types.
</entry>
<entry><literal>select * from json_to_record('{"a":1,"b":[1,2,3],"c":"bar"}',true) as x(a int, b text, d text) </literal></entry>
<entry>
<programlisting>
a | b | d
---+---------+---
1 | [1,2,3] |
</programlisting>
</entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_to_recordset</primary>
</indexterm>
<literal>json_to_recordset(json, nested_as_text bool)</literal>
</entry>
<entry><type>setof record</type></entry>
<entry>
json_to_recordset returns an arbitrary set of records from a JSON object. As with
json_to_record, the structure of the record must be explicitly defined when making the
call. However, with json_to_recordset the input JSON must be an array containing
objects. nested_as_text works as with json_to_record.
</entry>
<entry><literal>select * from json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","c":"bar"}]',true) as x(a int, b text);</literal></entry>
<entry>
<programlisting>
a | b
---+-----
1 | foo
2 |
</programlisting>
</entry>
</row>
</tbody>
</tgroup>
</table>
@ -10324,6 +10455,17 @@ table2-mapping
</para>
</note>
<note>
<para>
In json_to_record and json_to_recordset, type coercion from the JSON is
"best effort" and may not result in desired values for some types. JSON
elements are matched to identical field names in the record definition,
and elements which do not exist in the JSON will simply be NULL. JSON
elements which are not defined in the record template will
be omitted from the output.
</para>
</note>
<note>
<para>
The <xref linkend="hstore"> extension has a cast from <type>hstore</type> to
@ -11772,6 +11914,22 @@ NULL baz</literallayout>(3 rows)</entry>
<entry>aggregates records as a JSON array of objects</entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_object_agg</primary>
</indexterm>
<function>json_object_agg(<replaceable class="parameter">expression</replaceable>)</function>
</entry>
<entry>
<type>("any", "any")</type>
</entry>
<entry>
<type>json</type>
</entry>
<entry>aggregates name/value pairs as a JSON object</entry>
</row>
<row>
<entry>
<indexterm>