| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> |
| Cc: | "Gurgel, Flavio" <flavio(at)4linux(dot)com(dot)br>, Lefteris <lsidir(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org, Ivan Voras <ivoras(at)freebsd(dot)org> |
| Subject: | Re: Air-traffic benchmark |
| Date: | 2010-01-08 03:43:21 |
| Message-ID: | 25623.1262922201@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> writes:
> Can Pg even read partial records ? I thought it all operated on a page
> level, where if an index indicates that a particular value is present on
> a page the whole page gets read in and all records on the page are
> checked for the value of interest. No?
The whole page gets read, but we do know which record on the page
the index entry is pointing at.
(This statement is an oversimplification, because of lossy indexes
and lossy bitmap scans, but most of the time it's not a matter of
"checking all records on the page".)
regards, tom lane
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