Support for INCLUDE attributes in GiST indexes

Similarly to B-tree, GiST index access method gets support of INCLUDE
attributes.  These attributes aren't used for tree navigation and aren't
present in non-leaf pages.  But they are present in leaf pages and can be
fetched during index-only scan.

The point of having INCLUDE attributes in GiST indexes is slightly different
from the point of having them in B-tree.  The main point of INCLUDE attributes
in B-tree is to define UNIQUE constraint over part of attributes enabled for
index-only scan.  In GiST the main point of INCLUDE attributes is to use
index-only scan for attributes, whose data types don't have GiST opclasses.

Discussion: https://postgr.es/m/73A1A452-AD5F-40D4-BD61-978622FF75C1%40yandex-team.ru
Author: Andrey Borodin, with small changes by me
Reviewed-by: Andreas Karlsson

1 files changed, 36 insertions, 5 deletions

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 5ea774661a9..2ce5425ef98 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -75,7 +75,7 @@ gisthandler(PG_FUNCTION_ARGS)
 	amroutine->amclusterable = true;
 	amroutine->ampredlocks = true;
 	amroutine->amcanparallel = false;
-	amroutine->amcaninclude = false;
+	amroutine->amcaninclude = true;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = gistbuild;
@@ -1382,8 +1382,10 @@ gistSplit(Relation r,
 						IndexTupleSize(itup[0]), GiSTPageSize,
 						RelationGetRelationName(r))));
 
-	memset(v.spl_lisnull, true, sizeof(bool) * giststate->tupdesc->natts);
-	memset(v.spl_risnull, true, sizeof(bool) * giststate->tupdesc->natts);
+	memset(v.spl_lisnull, true,
+		   sizeof(bool) * giststate->nonLeafTupdesc->natts);
+	memset(v.spl_risnull, true,
+		   sizeof(bool) * giststate->nonLeafTupdesc->natts);
 	gistSplitByKey(r, page, itup, len, giststate, &v, 0);
 
 	/* form left and right vector */
@@ -1461,9 +1463,23 @@ initGISTstate(Relation index)
 
 	giststate->scanCxt = scanCxt;
 	giststate->tempCxt = scanCxt;	/* caller must change this if needed */
-	giststate->tupdesc = index->rd_att;
+	giststate->leafTupdesc = index->rd_att;
 
-	for (i = 0; i < index->rd_att->natts; i++)
+	/*
+	 * The truncated tupdesc for non-leaf index tuples, which doesn't contain
+	 * the INCLUDE attributes.
+	 *
+	 * It is used to form tuples during tuple adjustement and page split.
+	 * B-tree creates shortened tuple descriptor for every truncated tuple,
+	 * because it is doing this less often: it does not have to form truncated
+	 * tuples during page split.  Also, B-tree is not adjusting tuples on
+	 * internal pages the way GiST does.
+	 */
+	giststate->nonLeafTupdesc = CreateTupleDescCopyConstr(index->rd_att);
+	giststate->nonLeafTupdesc->natts =
+		IndexRelationGetNumberOfKeyAttributes(index);
+
+	for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(index); i++)
 	{
 		fmgr_info_copy(&(giststate->consistentFn[i]),
 					   index_getprocinfo(index, i + 1, GIST_CONSISTENT_PROC),
@@ -1531,6 +1547,21 @@ initGISTstate(Relation index)
 			giststate->supportCollation[i] = DEFAULT_COLLATION_OID;
 	}
 
+	/* No opclass information for INCLUDE attributes */
+	for (; i < index->rd_att->natts; i++)
+	{
+		giststate->consistentFn[i].fn_oid = InvalidOid;
+		giststate->unionFn[i].fn_oid = InvalidOid;
+		giststate->compressFn[i].fn_oid = InvalidOid;
+		giststate->decompressFn[i].fn_oid = InvalidOid;
+		giststate->penaltyFn[i].fn_oid = InvalidOid;
+		giststate->picksplitFn[i].fn_oid = InvalidOid;
+		giststate->equalFn[i].fn_oid = InvalidOid;
+		giststate->distanceFn[i].fn_oid = InvalidOid;
+		giststate->fetchFn[i].fn_oid = InvalidOid;
+		giststate->supportCollation[i] = InvalidOid;
+	}
+
 	MemoryContextSwitchTo(oldCxt);
 
 	return giststate;