Re: Possible to prevent transaction abort? - Mailing list pgsql-general

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.