Create a "sort support" interface API for faster sorting.

This patch creates an API whereby a btree index opclass can optionally
provide non-SQL-callable support functions for sorting.  In the initial
patch, we only use this to provide a directly-callable comparator function,
which can be invoked with a bit less overhead than the traditional
SQL-callable comparator.  While that should be of value in itself, the real
reason for doing this is to provide a datatype-extensible framework for
more aggressive optimizations, as in Peter Geoghegan's recent work.

Robert Haas and Tom Lane

1 files changed, 19 insertions, 0 deletions

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 45e70029e53..450dcd47277 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -1830,6 +1830,25 @@ timestamp_cmp(PG_FUNCTION_ARGS)
 	PG_RETURN_INT32(timestamp_cmp_internal(dt1, dt2));
 }
 
+/* note: this is used for timestamptz also */
+static int
+timestamp_fastcmp(Datum x, Datum y, SortSupport ssup)
+{
+	Timestamp	a = DatumGetTimestamp(x);
+	Timestamp	b = DatumGetTimestamp(y);
+
+	return timestamp_cmp_internal(a, b);
+}
+
+Datum
+timestamp_sortsupport(PG_FUNCTION_ARGS)
+{
+	SortSupport	ssup = (SortSupport) PG_GETARG_POINTER(0);
+
+	ssup->comparator = timestamp_fastcmp;
+	PG_RETURN_VOID();
+}
+
 Datum
 timestamp_hash(PG_FUNCTION_ARGS)
 {