From: Andrew Gierth <rhodiumtoad@postgresql.org>
Date: Tue, 24 Nov 2020 20:58:32 +0000 (+0000)
Subject: Properly check index mark/restore in ExecSupportsMarkRestore.
X-Git-Tag: REL_14_BETA1~1219
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=660b89928d18386de7755565c008439ae75d1218;p=postgresql.git

Properly check index mark/restore in ExecSupportsMarkRestore.

Previously this code assumed that all IndexScan nodes supported
mark/restore, which is not true since it depends on optional index AM
support functions. This could lead to errors about missing support
functions in rare edge cases of mergejoins with no sort keys, where an
unordered non-btree index scan was placed on the inner path without a
protecting Materialize node. (Normally, the fact that merge join
requires ordered input would avoid this error.)

Backpatch all the way since this bug is ancient.

Per report from Eugen Konkov on irc.

Discussion: https://postgr.es/m/87o8jn50be.fsf@news-spur.riddles.org.uk
---

diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index e2154ba86aa..0c10f1d35c2 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -417,6 +417,11 @@ ExecSupportsMarkRestore(Path *pathnode)
 	{
 		case T_IndexScan:
 		case T_IndexOnlyScan:
+			/*
+			 * Not all index types support mark/restore.
+			 */
+			return castNode(IndexPath, pathnode)->indexinfo->amcanmarkpos;
+
 		case T_Material:
 		case T_Sort:
 			return true;
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 52c01eb86b1..3e94256d34a 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -284,6 +284,8 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 			info->amhasgettuple = (amroutine->amgettuple != NULL);
 			info->amhasgetbitmap = amroutine->amgetbitmap != NULL &&
 				relation->rd_tableam->scan_bitmap_next_block != NULL;
+			info->amcanmarkpos = (amroutine->ammarkpos != NULL &&
+								  amroutine->amrestrpos != NULL);
 			info->amcostestimate = amroutine->amcostestimate;
 			Assert(info->amcostestimate != NULL);
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index abe6f570e32..5a10c1855d6 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -864,6 +864,7 @@ struct IndexOptInfo
 	bool		amhasgettuple;	/* does AM have amgettuple interface? */
 	bool		amhasgetbitmap; /* does AM have amgetbitmap interface? */
 	bool		amcanparallel;	/* does AM support parallel scan? */
+	bool		amcanmarkpos;	/* does AM support mark/restore? */
 	/* Rather than include amapi.h here, we declare amcostestimate like this */
 	void		(*amcostestimate) ();	/* AM's cost estimator */
 };