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commit    59ed45e278b78dbfae1b02ad90eee3d01ddec929
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 | 1 +
 src/include/nodes/relation.h         | 1 +
 3 files changed, 7 insertions(+)

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;
 
 


[parent: ded7db4c1ddd]