Help Center/ GaussDB(DWS)/ SQL Syntax Reference (8.1.3.x)/ Functions and Operators/ Set Returning Functions/ Subscript Generating Functions
Updated on 2024-09-30 GMT+08:00
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Subscript Generating Functions

generate_subscripts(array anyarray, dim int)

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

Return type: setof int

Example:

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-- basic usage
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:

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-- basic usage
SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1,TRUE) AS s;
 s
---
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 2
 1
(4 rows)

generate_subscripts is a function that generates the set of valid subscripts 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 subscripts are returned for NULL array elements). Example:

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-- 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 
---------
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       2
       3
       4
(4 rows)

-- Delete the function:
DROP FUNCTION unnest2;
Parent topic: Set Returning Functions