On 24 June 2014 11:32, David Rowley <dgrowle...@gmail.com> wrote: > So if anyone can point me in the right direction then that would be > really useful.
Many things can be added simply, but most things can't. It seems we just don't have that information. If we did, Tom would have done this already. > On a more positive or even slightly exciting note I think I've managed to > devise a way that ANTI JOINS can be used for NOT IN much more often. It > seems that find_nonnullable_vars will analyse a quals list to find > expressions that mean that the var cannot be NULL. This means we can perform > ANTI JOINS for NOT IN with queries like: > > SELECT * FROM a WHERE id NOT IN(SELECT nullable_col FROM b WHERE > nullable_col = 1); > or > SELECT * FROM a WHERE id NOT IN(SELECT nullable_col FROM b WHERE > nullable_col IS NOT NULL); > > (The attached patch implements this) > > the nullable_col =1 will mean that nullable_col cannot be NULL, so the ANTI > JOIN can be performed safely. I think this combined with the NOT NULL check > will cover probably just about all valid uses of NOT IN with a subquery... > unless of course I've assumed something wrongly about find_nonnullable_vars. > I just need the correct RangeTblEntry in order to determine if the > TargetEntry is from an out join. This is the better way to go. It's much better to have explicit proof its not null than a possibly long chain of metadata that might be buggy. > The attached patch is a broken implemention that still needs the lookup code > fixed to reference the correct RTE. The failing regression tests show where > the problems lie. > > Any help on this would be really appreciated. I'd suggest we just drop the targetlist approach completely. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
