Re: planner switch from index scan to seq scan?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bob Parkinson <rwp(at)biome(dot)ac(dot)uk>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: planner switch from index scan to seq scan?
Date: 2000-07-26 14:38:50
Message-ID: 10792.964622330@sss.pgh.pa.us
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Bob Parkinson <rwp(at)biome(dot)ac(dot)uk> writes:
> Is there are simple rule for when the planner switches over from doing an
> index scan to a seq scan?

Sure: when it thinks the seqscan is cheaper ;-)

The cost models on which this is based are not so simple, but you
can study them if you like, see src/backend/optimizer/path/costsize.c

regards, tom lane

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