Re: Abbreviated keys for Numeric

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От Andrew Gierth
Тема Re: Abbreviated keys for Numeric
Дата
Msg-id 87twygdqu9.fsf@news-spur.riddles.org.uk
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Ответ на Re: Abbreviated keys for Numeric (was: Re: B-Tree support function number 3 (strxfrm() optimization))  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Ответы Re: Abbreviated keys for Numeric  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
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>>>>> "Tomas" == Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> Right...so don't test a datum sort case, since that isn't supported>> at all in the master branch. Your test case is
invalidfor that>> reason.
 
Tomas> What do you mean by 'Datum sort case'?

A case where the code path goes via tuplesort_begin_datum rather than
tuplesort_begin_heap.
Tomas> The test I was using is this:
Tomas>    select percentile_disc(0) within group (order by randnum) from stuff;

Sorting single columns in aggregate calls uses the Datum sort path (in
fact I think it's currently the only place that does).

Do that test with _both_ the Datum and Numeric sort patches in place,
and you will see the effect. With only the Numeric patch, the numeric
abbrev code is not called.

If you want a test that works without the Datum patch, try:

select count(*) from (select randnum from stuff order by randnum) s;

-- 
Andrew (irc:RhodiumToad)



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