| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Greg Stark <gsstark(at)mit(dot)edu>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: the big picture for index-only scans |
| Date: | 2011-05-11 10:57:39 |
| Message-ID: | BANLkTinmqjbdQo4C0TAUbyLvmVbZ-Gn86A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, May 10, 2011 at 10:29 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> That will be true only if you intentionally ignore the points Greg
> raised. If the table isn't entirely ALL_VISIBLE, then the choice of
> index will determine the ordering of the actual table probes that occur.
> There could be more or fewer page reads, in a more or less optimal
> order, depending on the index used.
However, note that this wasn't one of the cases I said I was going to
try to optimize in the first go-around anyway.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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