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
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