PostgreSQL unnest() with element number

Question

When I have a column with separated values, I can use the unnest() function:

myTable
id | elements
---+------------
1  |ab,cd,efg,hi
2  |jk,lm,n         


        

Answer 1

unnest2() as exercise

Older versions before pg v8.4 need a user-defined unnest(). We can adapt this old function to return elements with an index:

CREATE FUNCTION unnest2(anyarray)
  RETURNS setof record  AS
$BODY$
  SELECT $1[i], i
  FROM   generate_series(array_lower($1,1),
                         array_upper($1,1)) i;
$BODY$ LANGUAGE sql IMMUTABLE;