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commit    321c87e5ca1a8a766a55ec4201099a37b9b0c68b
Author:   Andrew Gierth <rhodiumtoad@postgresql.org>
Date:     Tue Nov 24 20:58:32 2020 +0000
First released in: 14.0, 9.5.25, 9.6.21, 10.16, 11.11, 12.6, 13.2

    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


 src/backend/executor/execAmi.c       | 5 +++++
 src/backend/optimizer/util/plancat.c | 2 ++
 src/include/nodes/relation.h         | 1 +
 3 files changed, 8 insertions(+)

diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index f1636a5b883..1ab68f5cc91 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -413,6 +413,11 @@ 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 646e577272e..0c75b39d2be 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -249,6 +249,8 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 			info->amcanparallel = amroutine->amcanparallel;
 			info->amhasgettuple = (amroutine->amgettuple != NULL);
 			info->amhasgetbitmap = (amroutine->amgetbitmap != NULL);
+			info->amcanmarkpos = (amroutine->ammarkpos != NULL &&
+								  amroutine->amrestrpos != NULL);
 			info->amcostestimate = amroutine->amcostestimate;
 			Assert(info->amcostestimate != NULL);
 
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index f9b4067b1e7..3c7436cf27e 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -674,6 +674,7 @@ typedef 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 */
 } IndexOptInfo;


[parent: 1dbe627fd6bf]