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 e2154ba86aa5a2f0b0bf9047560a5e31924c6499..0c10f1d35c2b4301662dbda4dc799d69c60ff9f1 100644 (file)
--- 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 52c01eb86b17a7deb4c33d6cc023d9336198e1f5..3e94256d34a340d6569ffaec5cbe6055fe5330a9 100644 (file)
--- 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 abe6f570e3280354109f1a33c93114266c19dbc0..5a10c1855d66c059e488c6dd7e3849b4390e7abe 100644 (file)
--- 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 */
 };