Simon Riggs wrote:
Hmmm. I think it fits rather neatly with BitmapIndexScans. It would be
easy to apply the index condition and/or filters to see which segments
are excluded and then turn off bits in the bitmap appropriately.
Yeah, good point.
Not fully sure about IndexScans yet. I don't think it would be worth
trying to apply SE until we estimated we would return say 100 rows. It
needs to be able to work without slowing down the common path.
Yup.
Or
put it another way: SE is an optimization for sequential scans. For
tables where it works well, it could possibly replace the index entirely.
True
Without the index, you would rely on SE to always be able to exclude
enough segments, so that the seq scan is less expensive than an index
scan with the following table lookups.
It would have to be a very fat index scan for so large a table...
..for SE to be faster than an index scan, you mean? Yes.
Regards
Markus
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