Re: select max() much slower than select min()

Tom Lane [tgl(at)sss(dot)pgh(dot)pa(dot)us] wrote:
> Some experimentation suggests that it might help to provide a 2-column
> index on (ts_id, ts_interval_start_time). This is still going to be
> scanned in order by ts_id, but it will be possible to check the
> ts_interval_start_time condition in the index, eliminating a large
> number of useless trips to the heap. Whether this type of query is
> important enough to justify maintaining an extra index for is something
> you'll have to decide for yourself...

Thanks to all for the analysis and suggestions. Since the number of rows
in an hour < ~500,000, brute force looks to be a fast solution:

select ts_id from ... where ts_interval_start_time >= ... and ...

This query runs very fast as does a single pass through the ids to find
the min and max.

Brian