Subscript Generating Functions¶
generate_subscripts(array anyarray, dim int)¶
Description: Generates a series comprising the given array's subscripts.
Return type: setof int
Example:
SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s;
s
---
1
2
3
4
(4 rows)
generate_subscripts(array anyarray, dim int, reverse boolean)¶
Description: Generates a series comprising the given array's subscripts. When reverse is true, the series is returned in reverse order.
Return type: setof int
Example:
SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1,TRUE) AS s;
s
---
4
3
2
1
(4 rows)
generate_subscripts is a function that generates the set of valid subscripts for the specified dimension of a given array. Zero rows are returned for arrays that do not have the requested dimension, or for NULL arrays (but valid subscripts are returned for NULL array elements). Example:
-- unnest a 2D array
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;
SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
unnest2
---------
1
2
3
4
(4 rows)