Re: Struggling with EXCLUDE USING gist

On Sat, Jun 5, 2021 at 12:48 AM Laura Smith
 wrote:
>
> All the examples I've seen around the internet make this sound so easy.
>
> But I seem to be missing some important step because all I'm getting are messages such as "DETAIL:  Key (t_val, t_version)=(def, [-infinity,infinity)) conflicts with existing key (t_val, t_version)=(def, [-infinity,"2021-06-04 16:56:08.008122+01"))."
>
> [...]
>
> CREATE FUNCTION create_or_update_test(p_val text) RETURNS bool AS $$
> DECLARE
> v_version text;
> v_range tstzrange;
> BEGIN
> -- N.B. Have coded it this way round (not insert first) because "ON CONFLICT does not support deferrable unique constraints/exclusion constraints as arbiters"
> SELECT t_version,t_range into v_version,v_range  from test_v where t_val='abc';
> IF NOT FOUND THEN
>         INSERT INTO test(t_val) values(p_val)
> END IF;
> -- If range conflict, adjust old and set new
> UPDATE test set t_range=tstzrange(lower(v_range),now(),'[)') where t_version=v_version;
> INSERT INTO test(t_val) values(p_val);
> RETURN FOUND;
> END;
> $$ language plpgsql;

You need to provide more information.  I suspect that what's happening
is a concurrency issue where the create_or_update_test() is called
multiple time and both initially see and empty table so try to insert
an -infinity/infinity range before updating it, so the 2nd call will
fail once the 1st one commits.