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 9e784219786ac5192e71ed75808049851c82bf57..b01ef446734471f63f30f7018414b6000b1d3205 100644 (file)
--- 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 d99d1393fb46327000636917df9444f88ece692b..c8bab50e89c3b4ffca32c3dce52d1049159d9091 100644 (file)
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -275,6 +275,8 @@ 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 ffeb3eb1fee3ff5bd2e9c001d28b7d5024b9b297..098116b0d8b7152b56cfdb839d8e89b0e0359b13 100644 (file)
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -809,6 +809,7 @@ 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;