Обсуждение: planner switch from index scan to seq scan?

Is there are simple rule for when the planner switches over from doing an
index scan to a seq scan?

Cheers,

Bob

Bob Parkinson
rwp@biome.ac.uk
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Bob Parkinson <rwp@biome.ac.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