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Handle backward scan support for subquery RTEs #41

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Handle backward scan support for subquery RTEs #41

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12 changes: 11 additions & 1 deletion src/backend/executor/execAmi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -579,6 +579,16 @@ ExecSupportsBackwardScan(Plan *node, List *rtable)
((Scan *) node)->scanrelid <= list_length(rtable));

rte = rt_fetch(((Scan *) node)->scanrelid, rtable);

/*
* Subqueries and other non-table RTEs won't have a relid. They
* are already materialized or validated at this point, so
* assume backward scan is allowed and avoid calling
* TableSupportsBackwardScan with InvalidOid.
*/
if (!OidIsValid(rte->relid))
return true;

return TableSupportsBackwardScan(rte->relid);
}

Expand Down Expand Up @@ -648,7 +658,7 @@ TableSupportsBackwardScan(Oid tableid)
Form_pg_class tabrelrec;
const TableAmRoutine *amroutine;

/* Fetch the pg_class tuple of the index relation */
/* Fetch the pg_class tuple of the table relation */
ht_tabrel = SearchSysCache1(RELOID, ObjectIdGetDatum(tableid));
if (!HeapTupleIsValid(ht_tabrel))
elog(ERROR, "cache lookup failed for relation %u", tableid);
Expand Down