Re: Experiences of PostgreSQL on-disk bitmap index patch - Mailing list pgsql-general

From Chris Browne
Subject Re: Experiences of PostgreSQL on-disk bitmap index patch
Date
Msg-id 60zm2o2lhv.fsf@dba2.int.libertyrms.com
Whole thread Raw
In response to Experiences of PostgreSQL on-disk bitmap index patch  ("Christan Josefsson" <cjosefsson@gmail.com>)
Responses Re: Experiences of PostgreSQL on-disk bitmap index patch  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
cjosefsson@gmail.com ("Christan Josefsson") writes:
>     So you indicate that the so called bitmap index scan, a.k.a
>     in-memory bitmap indexes (right?), already adds such an
>     improvement when it comes to optimized response time on large
>     query sets (having the characteristics as normally used to
>     identify cases where bitmap indexes improves performance like:
>     low cardinality keys, large data volumes etc), so that the
>     on-disk indexes are not really needed or atleast not worth wile
>     implementing?

It looks very much like that may be the case...

Bitmap index scans have a somewhat different set of functionality, but
there is enough overlap that the cases where on-disk bitmap indexes
are useful (and in-memory bitmap scans aren't) look like rare edge
cases.

There may be users that see those "rare edge cases" all the time;
they'll find on-disk bitmap indexes worth having, and, possibly, worth
implementing.

But to be sure, there used to be a lot of "burning interest" in
on-disk bitmap indexes, and in-memory bitmap index scans have quenched
many of the flames...
--
"cbbrowne","@","cbbrowne.com"
http://linuxfinances.info/info/advocacy.html
">WindowsNT will not accept fecal matter in its diet... it's that simple.

I suppose that is a good ward against cannibalism." -- Nick Manka

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