Re: Possible to prevent transaction abort?

Adam B wrote:
> Hello all,
>
> Is it possible to prevent Postgre from aborting the transaction upon a
> constraint violation?
From the help files maybe the following could get you on the right track:

This example uses exception handling to perform either UPDATE or INSERT,
as appropriate:
CREATE TABLE db (a INT PRIMARY KEY, b TEXT);
CREATE FUNCTION merge_db(key INT, data TEXT) RETURNS VOID AS
$$
BEGIN
LOOP
-- first try to update the key
UPDATE db SET b = data WHERE a = key;
IF found THEN
RETURN;
END IF;
-- not there, so try to insert the key
-- if someone else inserts the same key concurrently,
-- we could get a unique-key failure
BEGIN
INSERT INTO db(a,b) VALUES (key, data);
RETURN;
EXCEPTION WHEN unique_violation THEN
-- do nothing, and loop to try the UPDATE again
END;
END LOOP;
END;
$$
LANGUAGE plpgsql;

HTH,

Johan Nel
Pretoria, South Africa.