index 875a4d84de026286b32e456d0d6851afce721905..77fb1991aebd003409406e6726bbb681f81a3ff5 100644 (file)
In some cases it is useful to define table functions that can
return different column sets depending on how they are invoked.
To support this, the table function can be declared as returning
- the pseudo-type <type>record</type>. When such a function is used in
+ the pseudo-type <type>record</type> with no <literal>OUT</literal>
+ parameters. When such a function is used in
a query, the expected row structure must be specified in the
query itself, so that the system can know how to parse and plan
the query. This syntax looks like:
that the parser knows, for example, what <literal>*</literal> should
expand to.
</para>
+
+ <para>
+ This example uses <literal>ROWS FROM</literal>:
+<programlisting>
+SELECT *
+FROM ROWS FROM
+ (
+ json_to_recordset('[{"a":40,"b":"foo"},{"a":"100","b":"bar"}]')
+ AS (a INTEGER, b TEXT),
+ generate_series(1, 3)
+ ) AS x (p, q, s)
+ORDER BY p;
+
+ p | q | s
+-----+-----+---
+ 40 | foo | 1
+ 100 | bar | 2
+ | | 3
+</programlisting>
+ It joins two functions into a single <literal>FROM</literal>
+ target. <function>json_to_recordset()</function> is instructed
+ to return two columns, the first <type>integer</type>
+ and the second <type>text</type>. The result of
+ <function>generate_series()</function> is used directly.
+ The <literal>ORDER BY</literal> clause sorts the column values
+ as integers.
+ </para>
</sect3>
<sect3 id="queries-lateral">