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: REL9_5_25~61
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=59ed45e278b78dbfae1b02ad90eee3d01ddec929;p=thirdparty%2Fpostgresql.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 93e1e9a691c..374dd6d8ac9 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -388,6 +388,11 @@ 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 ac57d0f2b89..2299f8af820 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -230,6 +230,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 			info->amsearchnulls = indexRelation->rd_am->amsearchnulls;
 			info->amhasgettuple = OidIsValid(indexRelation->rd_am->amgettuple);
 			info->amhasgetbitmap = OidIsValid(indexRelation->rd_am->amgetbitmap);
+			info->amcanmarkpos = (info->relam == BTREE_AM_OID);
 
 			/*
 			 * Fetch the ordering information for the index, if any.
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index a35ebe008e6..9debc364ad9 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -557,6 +557,7 @@ typedef struct IndexOptInfo
 	bool		amsearchnulls;	/* can AM search for NULL/NOT NULL entries? */
 	bool		amhasgettuple;	/* does AM have amgettuple interface? */
 	bool		amhasgetbitmap; /* does AM have amgetbitmap interface? */
+	bool		amcanmarkpos;	/* does AM support mark/restore? */
 } IndexOptInfo;