Suppose I have vacuum_values() function, which removes all "no longer referenced" by parent column. Kind of function to be run from time to time to clean table from crud. It looks like this:
I suppose you have a good reason to not use a foreign key with "ON DELETE CASCADE" ?
FOR r IN SELECT value_id FROM values NATURAL LEFT JOIN
other_tab WHERE other_tab.value_id IS NULL FOR UPDATE OF values LOOP
DELETE FROM values WHERE value_id = r.value_id;
END LOOP;
RETURN;
I don't remember the exact syntax (look in the DELETE docs) but you can certainly put a left join inside a delete and do it all at once with only one query, and it'll be faster to boot.
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
