Re: Trigger/Function - one solution - was constraint question (I think)

I would develop like this (No so many changes, it is basically a small
trigger)
create or replace function compound_rows_range_check() returns trigger as
$body$
DECLARE
BAYNO int4;
BEGIN
-- First Verification = if changing compound or row fail
IF (old.co_id <> new.co_id or
old.cr_id <> new.cr_id) THEN
RAISE EXCEPTION 'Cannot change co_id () | cr_id ()', old.co_id, old.cr_id;
END IF;

-- Last Verification
SELECT cb_id into BAYNO from compound_bays
where
co_id = NEW.co_id and
cr_id = NEW.cr_id and
cb_id > NEW.cr_length
order by cb_id desc
limit 1;

IF (FOUND) THEN
RAISE EXCEPTION 'Cannot remove occupied bays: % > %', BAYNO, NEW.cr_length;
END IF;

RETURN NEW;
END;
$body$
LANGUAGE 'plpgsql';

2008/12/4 Gary Stainburn <gary(dot)stainburn(at)ringways(dot)co(dot)uk>

> I have managed to develop one solution using functions and triggers. Has
> anyone got a better solution?
>
> Gary
>
> create unique index "compound_bays_unique_index" on compound_bays using
> btree
> (co_id,cr_id,cb_id);
>
> create or replace function compound_rows_range_check() returns trigger as
> $proc$
> DECLARE
> BAYNO int4;
> BEGIN
> -- if changing compound or row fail
> IF NEW.co_id <> OLD.co_id THEN
> RAISE EXCEPTION 'cannot change compound id';
> END IF;
> IF NEW.cr_id <> OLD.cr_id THEN
> RAISE EXCEPTION 'cannot change row id';
> END IF;
> SELECT cb_id into BAYNO from compound_bays where
> co_id = NEW.co_id and
> cr_id = NEW.cr_id and
> cb_id > NEW.cr_length
> order by cb_id desc
> limit 1;
> IF found THEN
> RAISE EXCEPTION 'Cannot remove occupied bays: % > %',
> BAYNO, NEW.cr_length;
> END IF;
> RETURN NEW;
> END;
> $proc$ LANGUAGE plpgsql;
>
> CREATE TRIGGER compound_rows_range_check BEFORE UPDATE on compound_rows
> FOR EACH ROW EXECUTE PROCEDURE compound_rows_range_check();
>
> create or replace function compound_bays_range_check() returns trigger as
> $proc$
> DECLARE
> ROWLENGTH int4;
> BEGIN
> SELECT cr_length into ROWLENGTH from compound_rows where
> co_id = NEW.co_id and
> cr_id = NEW.cr_id;
> IF not found THEN
> RAISE EXCEPTION 'Compound / Row not found';
> END IF;
> IF NEW.cb_id > ROWLENGTH THEN
> RAISE EXCEPTION 'row length exceeded: % > %',
> NEW.cb_id,ROWLENGTH;
> END IF;
> RETURN NEW;
> END;
> $proc$ LANGUAGE plpgsql;
>
> CREATE TRIGGER compound_bays_range_check BEFORE INSERT OR UPDATE on
> compound_bays
> FOR EACH ROW EXECUTE PROCEDURE compound_bays_range_check();
>
>
>
> --
> Gary Stainburn
>
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