Re: Inlining comparators as a performance optimisation

On Tue, Dec 6, 2011 at 12:06 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 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.

OK.  Well, then pushing it out to a separate file probably makes
sense.  Do you want to do that or shall I have a crack at it?  If the
latter, what do you think about using the name SortKey for everything
rather than SortSupport?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company