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Re: mosbench revisited

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Martijn van Oosterhout <kleptog(at)svana(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: mosbench revisited
Date: 2011-08-03 19:38:50
Message-ID: 22145.1312400330@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On a straight pgbench -S test, you get four system calls per query:
> recvfrom(), lseek(), lseek(), sendto().  Adding -M prepared eliminates
> the two lseeks.

[ scratches head... ]  Two?  Is that one for the table and one for its
lone index, or are we being redundant there?

(If the query ended up being a seqscan, I'd expect a second
lseek(SEEK_END) when the executor starts up, but I gather from the other
complaints that the mosbench people were only testing simple indexscan
queries.)

			regards, tom lane

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