Heikki Linnakangas <[email protected]> writes:
> On 21.12.2010 21:25, Jesper Krogh wrote:
>> Or is a Bitmap Heap Scan simply 3 times faster than a Seq-scan for
>> visibillity-testing?
> It certainly shouldn't be.
>> What have I missed in the logic?
> Perhaps you have a lot of empty space or dead tuples that don't match
> the query in the table, which the sequential scan has to grovel through,
> but the bitmap scan skips? What does EXPLAIN ANALYZE of both queries say?
Another possibility is that the seqscan is slowed by trying to operate
in a limited number of buffers (the buffer strategy stuff).
regards, tom lane
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