Add support for nearest-neighbor (KNN) searches to SP-GiST

Currently, KNN searches were supported only by GiST.  SP-GiST also capable to
support them.  This commit implements that support.  SP-GiST scan stack is
replaced with queue, which serves as stack if no ordering is specified.  KNN
support is provided for three SP-GIST opclasses: quad_point_ops, kd_point_ops
and poly_ops (catversion is bumped).  Some common parts between GiST and SP-GiST
KNNs are extracted into separate functions.

Discussion: https://postgr.es/m/570825e8-47d0-4732-2bf6-88d67d2d51c8%40postgrespro.ru
Author: Nikita Glukhov, Alexander Korotkov based on GSoC work by Vlad Sterzhanov
Review: Andrey Borodin, Alexander Korotkov

1 files changed, 5 insertions, 41 deletions

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index ad07b9e63c8..e4a3786be01 100644
--- a/src/backend/access/gist/gistget.c
+++ b/src/backend/access/gist/gistget.c
@@ -14,9 +14,9 @@
  */
 #include "postgres.h"
 
+#include "access/genam.h"
 #include "access/gist_private.h"
 #include "access/relscan.h"
-#include "catalog/pg_type.h"
 #include "miscadmin.h"
 #include "storage/lmgr.h"
 #include "storage/predicate.h"
@@ -543,7 +543,6 @@ getNextNearest(IndexScanDesc scan)
 {
 	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
 	bool		res = false;
-	int			i;
 
 	if (scan->xs_hitup)
 	{
@@ -564,45 +563,10 @@ getNextNearest(IndexScanDesc scan)
 			/* found a heap item at currently minimal distance */
 			scan->xs_ctup.t_self = item->data.heap.heapPtr;
 			scan->xs_recheck = item->data.heap.recheck;
-			scan->xs_recheckorderby = item->data.heap.recheckDistances;
-			for (i = 0; i < scan->numberOfOrderBys; i++)
-			{
-				if (so->orderByTypes[i] == FLOAT8OID)
-				{
-#ifndef USE_FLOAT8_BYVAL
-					/* must free any old value to avoid memory leakage */
-					if (!scan->xs_orderbynulls[i])
-						pfree(DatumGetPointer(scan->xs_orderbyvals[i]));
-#endif
-					scan->xs_orderbyvals[i] = Float8GetDatum(item->distances[i]);
-					scan->xs_orderbynulls[i] = false;
-				}
-				else if (so->orderByTypes[i] == FLOAT4OID)
-				{
-					/* convert distance function's result to ORDER BY type */
-#ifndef USE_FLOAT4_BYVAL
-					/* must free any old value to avoid memory leakage */
-					if (!scan->xs_orderbynulls[i])
-						pfree(DatumGetPointer(scan->xs_orderbyvals[i]));
-#endif
-					scan->xs_orderbyvals[i] = Float4GetDatum((float4) item->distances[i]);
-					scan->xs_orderbynulls[i] = false;
-				}
-				else
-				{
-					/*
-					 * If the ordering operator's return value is anything
-					 * else, we don't know how to convert the float8 bound
-					 * calculated by the distance function to that.  The
-					 * executor won't actually need the order by values we
-					 * return here, if there are no lossy results, so only
-					 * insist on converting if the *recheck flag is set.
-					 */
-					if (scan->xs_recheckorderby)
-						elog(ERROR, "GiST operator family's FOR ORDER BY operator must return float8 or float4 if the distance function is lossy");
-					scan->xs_orderbynulls[i] = true;
-				}
-			}
+
+			index_store_float8_orderby_distances(scan, so->orderByTypes,
+												 item->distances,
+												 item->data.heap.recheckDistances);
 
 			/* in an index-only scan, also return the reconstructed tuple. */
 			if (scan->xs_want_itup)