Ensure tableoid reads correctly in EvalPlanQual-manufactured tuples.

The ROW_MARK_COPY path in EvalPlanQualFetchRowMarks() was just setting
tableoid to InvalidOid, I think on the assumption that the referenced
RTE must be a subquery or other case without a meaningful OID.  However,
foreign tables also use this code path, and they do have meaningful
table OIDs; so failure to set the tuple field can lead to user-visible
misbehavior.  Fix that by fetching the appropriate OID from the range
table.

There's still an issue about whether CTID can ever have a meaningful
value in this case; at least with postgres_fdw foreign tables, it does.
But that is a different problem that seems to require a significantly
different patch --- it's debatable whether postgres_fdw really wants to
use this code path at all.

Simplified version of a patch by Etsuro Fujita, who also noted the
problem to begin with.  The issue can be demonstrated in all versions
having FDWs, so back-patch to 9.1.

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index a5d4a820ff06c0bf411d141dfa05d2dba114a518..bb7078d3f8c522a9800197c55c01056d9c27f123 100644 (file)
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -2407,7 +2407,9 @@ EvalPlanQualFetchRowMarks(EPQState *epqstate)
            /* build a temporary HeapTuple control structure */
            tuple.t_len = HeapTupleHeaderGetDatumLength(td);
            ItemPointerSetInvalid(&(tuple.t_self));
-           tuple.t_tableOid = InvalidOid;
+           /* relation might be a foreign table, if so provide tableoid */
+           tuple.t_tableOid = getrelid(erm->rti,
+                                       epqstate->estate->es_range_table);
            tuple.t_data = td;
 
            /* copy and store tuple */