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
