Specialize tuplesort routines for different kinds of abbreviated keys

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

1 files changed, 1 insertions, 17 deletions

diff --git a/src/backend/access/gist/gistproc.c b/src/backend/access/gist/gistproc.c
index 32fb32519ec..22f2c185370 100644
--- a/src/backend/access/gist/gistproc.c
+++ b/src/backend/access/gist/gistproc.c
@@ -37,7 +37,6 @@ static uint64 part_bits32_by2(uint32 x);
 static uint32 ieee_float32_to_uint32(float f);
 static int	gist_bbox_zorder_cmp(Datum a, Datum b, SortSupport ssup);
 static Datum gist_bbox_zorder_abbrev_convert(Datum original, SortSupport ssup);
-static int	gist_bbox_zorder_cmp_abbrev(Datum z1, Datum z2, SortSupport ssup);
 static bool gist_bbox_zorder_abbrev_abort(int memtupcount, SortSupport ssup);
 
 
@@ -1726,21 +1725,6 @@ gist_bbox_zorder_abbrev_convert(Datum original, SortSupport ssup)
 #endif
 }
 
-static int
-gist_bbox_zorder_cmp_abbrev(Datum z1, Datum z2, SortSupport ssup)
-{
-	/*
-	 * Compare the pre-computed Z-orders as unsigned integers. Datum is a
-	 * typedef for 'uintptr_t', so no casting is required.
-	 */
-	if (z1 > z2)
-		return 1;
-	else if (z1 < z2)
-		return -1;
-	else
-		return 0;
-}
-
 /*
  * We never consider aborting the abbreviation.
  *
@@ -1764,7 +1748,7 @@ gist_point_sortsupport(PG_FUNCTION_ARGS)
 
 	if (ssup->abbreviate)
 	{
-		ssup->comparator = gist_bbox_zorder_cmp_abbrev;
+		ssup->comparator = ssup_datum_unsigned_cmp;
 		ssup->abbrev_converter = gist_bbox_zorder_abbrev_convert;
 		ssup->abbrev_abort = gist_bbox_zorder_abbrev_abort;
 		ssup->abbrev_full_comparator = gist_bbox_zorder_cmp;