Re: NOT LIKE much faster than LIKE?

Hi,

> I did just think of something we could improve though. The pattern
> selectivity code doesn't make any use of the statistics about "most
> common values". For a constant pattern, we could actually apply the
> pattern test with each common value and derive answers that are exact
> for the portion of the population represented by the most-common-values
> list. If the MCV list covers a large fraction of the population then
> this would be a big leg up in accuracy. Dunno if that applies to your
> particular case or not, but it seems worth doing ...

This reminds me what I did in a patch which is currently on hold for the
next release:

http://momjian.postgresql.org/cgi-bin/pgpatches_hold
http://candle.pha.pa.us/mhonarc/patches_hold/msg00026.html

The patch was addressing a similar issue when using ltree <@ and @>
operator on an unbalanced tree.

Best regards
--
Matteo Beccati
http://phpadsnew.com
http://phppgads.com