PostgreSQL function - postgresql

Question

I've created this function to re-sequence the sequence number on a BOM table (bomitem).
CREATE OR REPLACE FUNCTION seqincr(integer)
RETURNS SETOF bomitem AS
$BODY$
DECLARE
pItemid ALIAS FOR $1;
_row bomitem%ROWTYPE;
seqint int;
_id int;
BEGIN
seqint=8;
FOR _row IN SELECT *
FROM bomitem
WHERE ((bomitem_parent_item_id=pItemid))
LOOP
RETURN NEXT _row;
_id = _row.bomitem_id;
seqint = seqint+2;
update bomitem set bomitem_seqnumber = seqint where bomitem_id=_id;
END LOOP;
RETURN;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;
ALTER FUNCTION seqincr(integer)
OWNER TO admin;
The example works on an individual bomitem_parent_item_id like below:
SELECT * from seqincr(14917);
I would like to rewrite this function to loop through
SELECT distinct bomitem_parent_item_id FROM bomitem;
so that it resequences the entire BOM table.

Answer 1

What you are trying to do is much simpler with a CTE:
WITH x AS (
SELECT bomitem_parent_item_id
, row_number() OVER (ORDER BY bomitem_parent_item_id) AS rn
FROM bomitem
GROUP BY bomitem_parent_item_id
ORDER BY bomitem_parent_item_id
)
UPDATE bomitem b
SET bomitem_seqnumber = 8 + 2 * rn
FROM x
WHERE x.bomitem_parent_item_id = b.bomitem_id;
You need at least PostgreSQL 9.1 for data-modifying CTE.
Or use a subquery, works in earlier versions, too:
UPDATE bomitem b
SET bomitem_seqnumber = 8 + 2 * rn
FROM (
SELECT bomitem_parent_item_id
, row_number() OVER (ORDER BY bomitem_parent_item_id) AS rn
FROM bomitem
GROUP BY bomitem_parent_item_id
ORDER BY bomitem_parent_item_id
) x
WHERE x.bomitem_parent_item_id = b.bomitem_id;
But you need at least PostgreSQL 8.4 for the window function row_number().