1 files changed, 45 insertions, 1 deletions

diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index bdc410d1a35..35c27e7fb3c 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -1571,13 +1571,38 @@ deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
 {
 	RangeTblEntry *rte;
 
-	/* varattno can be a whole-row reference, ctid or a regular table column */
 	if (varattno == SelfItemPointerAttributeNumber)
 	{
+		/* We support fetching the remote side's CTID. */
 		if (qualify_col)
 			ADD_REL_QUALIFIER(buf, varno);
 		appendStringInfoString(buf, "ctid");
 	}
+	else if (varattno < 0)
+	{
+		/*
+		 * All other system attributes are fetched as 0, except for table OID,
+		 * which is fetched as the local table OID.  However, we must be
+		 * careful; the table could be beneath an outer join, in which case
+		 * it must go to NULL whenever the rest of the row does.
+		 */
+		Oid		fetchval = 0;
+
+		if (varattno == TableOidAttributeNumber)
+		{
+			rte = planner_rt_fetch(varno, root);
+			fetchval = rte->relid;
+		}
+
+		if (qualify_col)
+		{
+			appendStringInfoString(buf, "CASE WHEN ");
+			ADD_REL_QUALIFIER(buf, varno);
+			appendStringInfo(buf, "* IS NOT NULL THEN %u END", fetchval);
+		}
+		else
+			appendStringInfo(buf, "%u", fetchval);
+	}
 	else if (varattno == 0)
 	{
 		/* Whole row reference */
@@ -1606,10 +1631,29 @@ deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
 		 */
 		attrs_used = bms_add_member(NULL,
 									0 - FirstLowInvalidHeapAttributeNumber);
+
+		/*
+		 * In case the whole-row reference is under an outer join then it has to
+		 * go NULL whenver the rest of the row goes NULL. Deparsing a join query
+		 * would always involve multiple relations, thus qualify_col would be
+		 * true.
+		 */
+		if (qualify_col)
+		{
+			appendStringInfoString(buf, "CASE WHEN ");
+			ADD_REL_QUALIFIER(buf, varno);
+			appendStringInfo(buf, "* IS NOT NULL THEN ");
+		}
+
 		appendStringInfoString(buf, "ROW(");
 		deparseTargetList(buf, root, varno, rel, false, attrs_used, qualify_col,
 						  &retrieved_attrs);
 		appendStringInfoString(buf, ")");
+
+		/* Complete the CASE WHEN statement started above. */
+		if (qualify_col)
+			appendStringInfo(buf," END");
+
 		heap_close(rel, NoLock);
 		bms_free(attrs_used);
 	}