On Sun, Sep 6, 2015 at 9:35 PM, Thomas Munro <thomas.mu...@enterprisedb.com> wrote: > Running various contrived aggregate queries on a large low cardinality > dataset in a small range (therefore frequently the same weight & size), I > managed to measure a small improvement of up to a few percent with the > attached patch. I also wonder whether numeric_cmp could be profitably > implemented with memcmp on big endian systems and some unrolled loops on > little endian systems when size & weight match.
I think that setting up numeric SortSupport to have scratch memory used across authoritative numeric comparator calls would also help. We should prefer to do this kind of thing in a datatype independent way, of course. I'm not opposed to doing what you outline too, but I don't think it will be especially helpful for the cases here. I think that what you're talking about would live in the SortSupport authoritative comparator, and would benefit non-leading-attribute comparisons most. > Of course there are a ton of other overheads involved with numeric. I > wonder how crazy or difficult it would be to make it so that we could > optionally put a pass-by-value NUMERIC in a Datum, setting a low order tag > bit to say 'I'm an immediate value, not a pointer', and then packing 3 > digits (= 12 significant figures) + sign + weight into the other 63 bits. That seems possible, but very invasive. I'd want to get a good sense of the pay-off before undertaking such a project. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
