From:
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To:
"Simon Riggs" <simon(at)2ndQuadrant(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc:
"Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "decibel" <decibel(at)decibel(dot)org>, "Itagaki Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, "pgsql-hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject:
Re: FSM search modes
Date:
2009-10-01 18:36:34
Message-ID:
4AC4B062020000250002B550@gw.wicourts.gov (view raw or flat )
Thread:
2009-09-17 15:26:19 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2009-09-18 01:47:39 from Itagaki Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
2009-09-18 06:09:15 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2009-09-18 06:57:50 from decibel <decibel(at)decibel(dot)org>
2009-09-30 22:13:04 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 15:24:37 from decibel <decibel(at)decibel(dot)org>
2009-10-01 15:56:09 from Alvaro Herrera <alvherre(at)commandprompt(dot)com>
2009-10-01 16:05:40 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-01 16:28:08 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2009-10-01 16:31:43 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-01 16:32:08 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 16:42:15 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2009-10-01 16:45:03 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2009-10-01 16:55:03 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-01 18:36:34 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 18:55:18 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-01 19:23:15 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2009-10-01 19:43:14 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 20:07:51 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 20:47:59 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-01 21:09:33 from Robert Haas <robertmhaas(at)gmail(dot)com>
2009-10-01 22:07:41 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 22:17:20 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-01 22:49:45 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-02 14:03:01 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-10-03 03:33:49 from Bruce Momjian <bruce(at)momjian(dot)us>
2009-10-01 20:46:26 from Robert Haas <robertmhaas(at)gmail(dot)com>
2009-10-01 21:08:12 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2009-10-01 21:18:54 from Robert Haas <robertmhaas(at)gmail(dot)com>
2009-10-02 19:59:19 from decibel <decibel(at)decibel(dot)org>
2009-10-01 22:02:28 from Dimitri Fontaine <dfontaine(at)hi-media(dot)com>
2009-10-02 06:53:51 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2009-10-01 21:23:52 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2009-09-18 12:43:20 from Hannu Krosing <hannu(at)2ndQuadrant(dot)com>
2009-09-18 19:44:34 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
Lists:
pgsql-hackers
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
>> Yes, as Tom points out, this must be done with bias away from the
>> very end of the table.
>
>> I meant that we should start from the beginning of large spaces and
>> that we shouldn't assume that all space worth filling is at start
>> of relation.
OK, so I did misunderstand you; we agree after all. :-)
> So for example we might try resetting the search to the start of the
> relation with probability 0.01.
If I understand the heuristic you propose, and my math skill haven't
eroded too badly from lack of use, every 229 spots considered would
cause a 90% chance of reset. That means that the odds of getting past
50,000 spots (the number of pages with available free space at which I
generally start to get worried) without resetting is about 1 in 10^218
-- which is a risk I'm willing to accept. ;-)
-Kevin
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