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Specialize tuplesort routines for different kinds of abbreviated keys

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Previously, the specialized tuplesort routine inlined handling for
reverse-sort and NULLs-ordering but called the datum comparator via a
pointer in the SortSupport struct parameter. Testing has showed that we
can get a useful performance gain by specializing datum comparison for
the different representations of abbreviated keys -- signed and unsigned
64-bit integers and signed 32-bit integers. Almost all abbreviatable data
types will benefit -- the only exception for now is numeric, since the
datum comparison is more complex. The performance gain depends on data
type and input distribution, but often falls in the range of 10-20% faster.

Thomas Munro

Reviewed by Peter Geoghegan, review and performance testing by me

Discussion:
https://www.postgresql.org/message-id/CA%2BhUKGKKYttZZk-JMRQSVak%3DCXSJ5fiwtirFf%3Dn%3DPAbumvn1Ww%40mail.gmail.com
This commit is contained in:
John Naylor
2022-04-02 15:22:25 +07:00
parent db086de5ab
commit 6974924347
10 changed files with 308 additions and 132 deletions
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23
src/backend/utils/adt/mac.c
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@@ -44,7 +44,6 @@ typedef struct
static int macaddr_cmp_internal(macaddr *a1, macaddr *a2);
static int macaddr_fast_cmp(Datum x, Datum y, SortSupport ssup);
static int macaddr_cmp_abbrev(Datum x, Datum y, SortSupport ssup);
static bool macaddr_abbrev_abort(int memtupcount, SortSupport ssup);
static Datum macaddr_abbrev_convert(Datum original, SortSupport ssup);
@@ -381,7 +380,7 @@ macaddr_sortsupport(PG_FUNCTION_ARGS)
ssup->ssup_extra = uss;
ssup->comparator = macaddr_cmp_abbrev;
ssup->comparator = ssup_datum_unsigned_cmp;
ssup->abbrev_converter = macaddr_abbrev_convert;
ssup->abbrev_abort = macaddr_abbrev_abort;
ssup->abbrev_full_comparator = macaddr_fast_cmp;
@@ -405,22 +404,6 @@ macaddr_fast_cmp(Datum x, Datum y, SortSupport ssup)
return macaddr_cmp_internal(arg1, arg2);
}
/*
* SortSupport abbreviated key comparison function. Compares two MAC addresses
* quickly by treating them like integers, and without having to go to the
* heap.
*/
static int
macaddr_cmp_abbrev(Datum x, Datum y, SortSupport ssup)
{
if (x > y)
return 1;
else if (x == y)
return 0;
else
return -1;
}
/*
* Callback for estimating effectiveness of abbreviated key optimization.
*
@@ -537,8 +520,8 @@ macaddr_abbrev_convert(Datum original, SortSupport ssup)
/*
* Byteswap on little-endian machines.
*
* This is needed so that macaddr_cmp_abbrev() (an unsigned integer 3-way
* comparator) works correctly on all platforms. Without this, the
* This is needed so that ssup_datum_unsigned_cmp() (an unsigned integer
* 3-way comparator) works correctly on all platforms. Without this, the
* comparator would have to call memcmp() with a pair of pointers to the
* first byte of each abbreviated key, which is slower.
*/