> Thomas is correct on this. Vadim has run some tests, and with our
> optimized psort() code, the in-memory sort is often faster than using
> the index to get the tuple, because you are jumping all over the drive.
> I don't remember, but obviously there is a break-even point where
> getting X rows using the index on a table of Y rows is faster , but
> getting X+1 rows on a table of Y rows is faster getting all the rows
> sequentailly, and doing the sort.
>
> You would have to pick only certain queries(no joins, index matches
> ORDER BY), take the number of rows requested, and the number of rows
> selected, and figure out if it is faster to use the index, or a
> sequential scan and do the ORDER BY yourself.
Since a sort loads the data into memory anyway, how about speeding up the
sort by using the index? Or does that take up too much memory? (approx 40%
more than the data alone, I think)
TAra
