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Clarify array generate_subscripts() documentation example.

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Tim Landscheidt
This commit is contained in:
Bruce Momjian 2010-06-03 02:06:10 +00:00
parent 9b5c3611d7
commit 356e4dbf9a
1 changed files with 18 additions and 17 deletions
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35
doc/src/sgml/func.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.514 2010/06/03 01:34:02 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.515 2010/06/03 02:06:10 momjian Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -11419,7 +11419,7 @@ SELECT * FROM generate_series('2008-03-01 00:00'::timestamp,
elements). Some examples follow:
<programlisting>
-- basic usage
select generate_subscripts('{NULL,1,NULL,2}'::int[], 1) as s;
SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s;
s
---
1
@ -11430,32 +11430,33 @@ select generate_subscripts('{NULL,1,NULL,2}'::int[], 1) as s;
-- presenting an array, the subscript and the subscripted
-- value requires a subquery
select * from arrays;
SELECT * FROM arrays;
a
--------------------
{-1,-2}
{100,200}
{100,200,300}
(2 rows)
select a as array, s as subscript, a[s] as value
from (select generate_subscripts(a, 1) as s, a from arrays) foo;
array | subscript | value
-----------+-----------+-------
{-1,-2} | 1 | -1
{-1,-2} | 2 | -2
{100,200} | 1 | 100
{100,200} | 2 | 200
(4 rows)
SELECT a AS array, s AS subscript, a[s] AS value
FROM (SELECT generate_subscripts(a, 1) AS s, a FROM arrays) foo;
array | subscript | value
---------------+-----------+-------
{-1,-2} | 1 | -1
{-1,-2} | 2 | -2
{100,200,300} | 1 | 100
{100,200,300} | 2 | 200
{100,200,300} | 3 | 300
(5 rows)
-- unnest a 2D array
create or replace function unnest2(anyarray)
returns setof anyelement as $$
CREATE OR REPLACE FUNCTION unnest2(anyarray)
RETURNS SETOF anyelement AS $$
select $1[i][j]
from generate_subscripts($1,1) g1(i),
generate_subscripts($1,2) g2(j);
$$ language sql immutable;
$$ LANGUAGE sql IMMUTABLE;
CREATE FUNCTION
postgres=# select * from unnest2(array[[1,2],[3,4]]);
postgres=# SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
unnest2
---------
1