Re: Inlining comparators as a performance optimisation

Robert Haas <robertmhaas@gmail.com> writes:
> On Sun, Dec 4, 2011 at 2:17 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> * We're going to want to expose PrepareSortSupportComparisonShim
>> for use outside tuplesort.c too, and possibly refactor
>> tuplesort_begin_heap so that the SortKey setup logic inside it
>> can be extracted for use elsewhere.  Shall we just add those to
>> tuplesort's API, or would it be better to create a sortsupport.c
>> with these sorts of functions?

> Why are we going to want to do that?  If it's because there are other
> places in the code that can make use of a fast comparator that don't
> go through tuplesort.c, then we should probably break it off into a
> separate file (sortkey.c?).  But if it's because we think that clients
> of the tuplesort code are going to need it for some reason, then we
> may as well keep it in tuplesort.c.

My expectation is that nbtree, as well as mergejoin and mergeappend,
would get converted over to use the fast comparator API.  I looked at
that a little bit but didn't push it far enough to be very sure about
whether they'd be able to share the initialization code from
tuplesort_begin_heap.  But they're definitely going to need the shim
function for backwards compatibility, and
PrepareSortSupportComparisonShim was my first cut at a wrapper that
would be generally useful.
        regards, tom lane