Creates a grid of `xsize*ysize` cells in a given extent

st_createfishnet.sql

CREATE OR REPLACE FUNCTION ST_CreateFishNet(
    IN xsize double precision,
    IN ysize double precision,
    IN north double precision DEFAULT 0,
    IN east double precision DEFAULT 0,
    IN south double precision DEFAULT 1,
    IN west double precision DEFAULT 1)
  RETURNS SETOF geometry AS
$BODY$
SELECT ST_Translate(cell, $6 + (i * $1), $5 + (j * $2)) AS geom
FROM generate_series(0, (($4 - $6) / $1)::integer) AS i,
     generate_series(0, (($3 - $5) / $2)::integer) AS j,
(
SELECT ('POLYGON((0 0, 0 '||$2||', '||$1||' '||$2||', '||$1||' 0,0 0))')::geometry AS cell
) AS foo;
$BODY$
  LANGUAGE sql IMMUTABLE STRICT;