Oleg Bartunov wrote:
You could increase statistics or try contrib/tsearch2
Oleg
On Fri, 7 Oct 2005, han.holl@xxxxxxxxxxxxxxxxxxxx wrote:
Hello,
We have a table of people with a date-of-birth and a surname, both
indexed.
We have queries like this:
select report from table where dateofbirth = '1966-12-12' and surname
like
'boer%'
The planner estimates that in a 1.5M record table 'boer%' will have
one record
and 1966-12-12 about 40.
Unfortunately, names are not evenly distributed, and in some
combinations it
will have to process many thousands of records. On some older and slower
systems, this hurts.
Is there a way to tell the planner to always prefer the dateofbirth
index ?
Alternatively, to inform it about the wildly uneven distribution of
surnames
(this must be even worse in China).
A third possibility would be to rewrite such a query as a nested
query: is
there a rewrite query - hook (like apaches mod_rewrite) available ? Or is
there a somewhere a proxy-server that could do this ?
Cheers,
Han Holl
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TIP 6: explain analyze is your friend
Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@xxxxxxxxxx, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
You can also "force" it to use the index using ORDER BY dateofbirth.
Cheers,
Ben-Nes Yonatan
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TIP 2: Don't 'kill -9' the postmaster
