| From: | Sailesh Krishnamurthy <sailesh(at)cs(dot)berkeley(dot)edu> |
|---|---|
| To: | Gavin Sherry <swm(at)linuxworld(dot)com(dot)au> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Mark Kirkwood <markir(at)coretech(dot)co(dot)nz>, josh(at)agliodbs(dot)com, pgsql-hackers(at)postgresql(dot)org, Chris Browne <cbbrowne(at)acm(dot)org> |
| Subject: | Re: plans for bitmap indexes? |
| Date: | 2004-10-20 15:39:02 |
| Message-ID: | mjqsm89jt61.fsf@drones.CS.Berkeley.EDU |
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| Lists: | pgsql-hackers |
>>>>> "Gavin" == Gavin Sherry <swm(at)linuxworld(dot)com(dot)au> writes:
Gavin> I'm uncertain about the potential benefit of
Gavin> this. Isn't/shouldn't the effects of caching be assisting
Gavin> us here?
It all depends on how large your table is, and how busy the system is
(other pressures on the cache). While it's difficult to plan for the
latter you can plan for the former. For the latter you could assume
that the effective cache size is some fraction of the real size to
account for the effects of other queries. Unless you are real sure
that you will never kick out a page from the buffer cache ..
I believe that for large enough tables this can certainly help .. it
sure is something that many other systems have implemented.
--
Pip-pip
Sailesh
http://www.cs.berkeley.edu/~sailesh
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