Tom Lane wrote:
> A bad estimate for physical-position correlation has only limited
> impact,
Ah! This seems very true with 8.3 but much less true with 8.0.
On a legacy 8.0 system I have a hard time avoiding cases where
a query like "select * from addresses where add_state_or_province = 'CA';"
does a 2-second full-table scan instead of a 300ms index scan
thanks to a poor physical order guess.
I just sucked the table into 8.3 and am pleased to say that
it picks a 200ms bitmap scan even with the misleading correlation.
Thanks for bitmap scans guys!
I'll shut up about this physical ordering stuff now
and try to do better upgrading before posting.
