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JSON generation improvements.

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This adds the following:

    json_agg(anyrecord) -> json
    to_json(any) -> json
    hstore_to_json(hstore) -> json (also used as a cast)
    hstore_to_json_loose(hstore) -> json

The last provides heuristic treatment of numbers and booleans.

Also, in json generation, if any non-builtin type has a cast to json,
that function is used instead of the type's output function.

Andrew Dunstan, reviewed by Steve Singer.

Catalog version bumped.
This commit is contained in:
Andrew Dunstan
2013-03-10 17:35:36 -04:00
parent dd28c410f7
commit 38fb4d978c
13 changed files with 699 additions and 21 deletions
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48
doc/src/sgml/func.sgml
View File

@@ -9685,10 +9685,41 @@ table2-mapping
<entry><literal>row_to_json(row(1,'foo'))</literal></entry>
<entry><literal>{"f1":1,"f2":"foo"}</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>to_json</primary>
</indexterm>
<literal>to_json(anyelement)</literal>
</entry>
<entry>
Returns the value as JSON. If the data type is not builtin, and there
is a cast from the type to json, the cast function will be used to
perform the conversion. Otherwise, for any value other than a number,
a boolean or NULL, the text representation will be used, escaped and
quoted so that it is legal JSON.
</entry>
<entry><literal>to_json('Fred said "Hi."'</literal></entry>
<entry><literal>"Fred said \"Hi.\""</literal></entry>
</row>
</tbody>
</tgroup>
</table>
<note>
<para>
The <xref linkend="hstore"> extension has a cast from hstore to
json, so that converted hstore values are represented as json objects,
not as string values.
</para>
</note>
<para>
See also <xref linkend="functions-aggregate"> about the aggregate
function <function>json_agg</function> which aggregates record
values as json efficiently.
</para>
</sect1>
<sect1 id="functions-sequence">
@@ -11059,6 +11090,22 @@ SELECT NULLIF(value, '(none)') ...
<entry>equivalent to <function>bool_and</function></entry>
</row>
<row>
<entry>
<indexterm>
<primary>json_agg</primary>
</indexterm>
<function>json_agg(<replaceable class="parameter">record</replaceable>)</function>
</entry>
<entry>
<type>record</type>
</entry>
<entry>
<type>json</type>
</entry>
<entry>aggregates records as a json array of objects</entry>
</row>
<row>
<entry>
<indexterm>
@@ -11204,6 +11251,7 @@ SELECT count(*) FROM sometable;
<para>
The aggregate functions <function>array_agg</function>,
<function>json_agg</function>,
<function>string_agg</function>,
and <function>xmlagg</function>, as well as similar user-defined
aggregate functions, produce meaningfully different result values

23
doc/src/sgml/hstore.sgml
View File

@@ -322,6 +322,22 @@ b
<entry><literal>{{a,1},{b,2}}</literal></entry>
</row>
<row>
<entry><function>hstore_to_json(hstore)</function></entry>
<entry><type>json</type></entry>
<entry>get <type>hstore</type> as a json value</entry>
<entry><literal>hstore_to_json('"a key"=&gt;1, b=&gt;t, c=&gt;null, d=&gt;12345, e=&gt;012345, f=&gt;1.234, g=&gt;2.345e+4')</literal></entry>
<entry><literal>{"a key": "1", "b": "t", "c": null, "d": "12345", "e": "012345", "f": "1.234", "g": "2.345e+4"}</literal></entry>
</row>
<row>
<entry><function>hstore_to_json_loose(hstore)</function></entry>
<entry><type>json</type></entry>
<entry>get <type>hstore</type> as a json value, but attempting to distinguish numerical and boolean values so they are unquoted in the json</entry>
<entry><literal>hstore_to_json('"a key"=&gt;1, b=&gt;t, c=&gt;null, d=&gt;12345, e=&gt;012345, f=&gt;1.234, g=&gt;2.345e+4')</literal></entry>
<entry><literal>{"a key": 1, "b": true, "c": null, "d": 12345, "e": "012345", "f": 1.234, "g": 2.345e+4}</literal></entry>
</row>
<row>
<entry><function>slice(hstore, text[])</function></entry>
<entry><type>hstore</type></entry>
@@ -396,6 +412,13 @@ b
</tgroup>
</table>
<note>
<para>
The function <function>hstore_to_json</function> is used when an <type>hstore</type>
value is cast to <type>json</type>.
</para>
</note>
<note>
<para>
The function <function>populate_record</function> is actually declared