From:
Claudio Freire <klaussfreire(at)gmail(dot)com>
To:
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc:
Simon Riggs <simon(at)2ndquadrant(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject:
Re: [PERFORM] Slow query: bitmap scan troubles
Date:
2013-01-07 18:48:12
Message-ID:
CAGTBQpbNJLx+QjksoA4wmChBDkzkBgfxXLDkgaKKrku+JfvqXg@mail.gmail.com (view raw or flat )
Thread:
2012-12-04 15:06:48 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 15:21:17 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 15:27:57 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2012-12-04 17:22:29 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-04 17:25:56 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2012-12-04 17:35:32 from "Philip Scott" <pscott(at)foo(dot)me(dot)uk>
2012-12-04 17:47:29 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 18:50:41 from Vitalii Tymchyshyn <tivv00(at)gmail(dot)com>
2012-12-04 18:55:17 from "Philip Scott" <pscott(at)foo(dot)me(dot)uk>
2012-12-04 18:56:04 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 20:11:53 from Sergey Konoplev <gray(dot)ru(at)gmail(dot)com>
2012-12-06 12:56:26 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 22:34:42 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-04 18:03:29 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 18:31:50 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2012-12-04 23:42:21 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-05 17:39:35 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-05 17:43:49 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2012-12-06 17:27:48 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-06 20:05:09 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2012-12-06 21:09:54 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-05 18:05:10 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2012-12-06 12:52:07 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-18 06:00:16 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2013-01-05 22:18:16 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-06 16:29:17 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2013-01-06 18:18:03 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-06 18:22:33 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2013-01-06 18:19:10 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2013-01-06 18:58:40 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-06 19:47:48 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2013-01-06 23:03:05 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-06 23:17:23 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-07 00:03:04 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2013-01-07 17:35:51 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-07 18:03:37 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2013-01-07 18:27:38 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-07 18:48:12 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2013-01-11 01:07:34 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-14 16:45:01 from Robert Haas <robertmhaas(at)gmail(dot)com>
2013-01-14 17:23:17 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-14 17:50:24 from Robert Haas <robertmhaas(at)gmail(dot)com>
2013-01-14 17:56:37 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2013-01-15 19:46:39 from Bruce Momjian <bruce(at)momjian(dot)us>
2013-01-15 20:11:02 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2012-12-19 01:05:05 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-19 14:40:54 from Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
2012-12-06 14:10:29 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-08 15:15:42 from Guillaume Lelarge <guillaume(at)lelarge(dot)info>
2012-12-10 09:52:42 from <postgresql(at)foo(dot)me(dot)uk>
2012-12-04 18:31:05 from "Philip Scott" <pscott(at)foo(dot)me(dot)uk>
2012-12-04 18:32:57 from Claudio Freire <klaussfreire(at)gmail(dot)com>
2012-12-04 18:54:29 from <postgresql(at)foo(dot)me(dot)uk>
Lists:
pgsql-hackers pgsql-performance
On Mon, Jan 7, 2013 at 3:27 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> One issue that needs some thought is that the argument for this formula
> is based entirely on thinking about b-trees. I think it's probably
> reasonable to apply it to gist, gin, and sp-gist as well, assuming we
> can get some estimate of tree height for those, but it's obviously
> hogwash for hash indexes. We could possibly just take H=0 for hash,
> and still apply the log2(N) part ... not so much because that is right
> as because it's likely too small to matter.
Height would be more precisely "lookup cost" (in comparisons). Most
indexing structures have a well-studied lookup cost. For b-trees, it's
log_b(size), for hash it's 1 + size/buckets.
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