Index Generating Functions

generate_subscripts(array anyarray, dim int)

Description: Generates a series comprising the given array's indexes.

Return type: setof int

generate_subscripts(array anyarray, dim int, reverse boolean)

Description: Generates a series comprising the given array's indexes. When reverse is true, the series is returned in reverse order.

Return type: setof int

generate_subscripts is a function that generates the set of valid indexes for the specified dimension of the given array. Zero rows are returned for arrays that do not have the requested dimension, or for NULL arrays (but valid indexes are returned for NULL array elements). Example:

   
        -- Basic usage
gaussdb=# SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s;
 s 
---
 1
 2
 3
 4
(4 rows)

   
        -- Unnest a 2D array.
gaussdb=# 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;

gaussdb=# SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]);
 unnest2 
---------
       1
       2
       3
       4
(4 rows)

-- Delete the function.
gaussdb=# DROP FUNCTION unnest2;