1 files changed, 54 insertions, 0 deletions
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 69dd327f0c9..cd540a0df5b 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -851,6 +851,60 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 						fix_scan_list(root, splan->exclRelTlist, rtoffset);
 				}
 
+				/*
+				 * The MERGE produces the target rows by performing a right
+				 * join between the target relation and the source relation
+				 * (which could be a plain relation or a subquery). The INSERT
+				 * and UPDATE actions of the MERGE requires access to the
+				 * columns from the source relation. We arrange things so that
+				 * the source relation attributes are available as INNER_VAR
+				 * and the target relation attributes are available from the
+				 * scan tuple.
+				 */
+				if (splan->mergeActionList != NIL)
+				{
+					/*
+					 * mergeSourceTargetList is already setup correctly to
+					 * include all Vars coming from the source relation. So we
+					 * fix the targetList of individual action nodes by
+					 * ensuring that the source relation Vars are referenced
+					 * as INNER_VAR. Note that for this to work correctly,
+					 * during execution, the ecxt_innertuple must be set to
+					 * the tuple obtained from the source relation.
+					 *
+					 * We leave the Vars from the result relation (i.e. the
+					 * target relation) unchanged i.e. those Vars would be
+					 * picked from the scan slot. So during execution, we must
+					 * ensure that ecxt_scantuple is setup correctly to refer
+					 * to the tuple from the target relation.
+					 */
+
+					indexed_tlist *itlist;
+
+					itlist = build_tlist_index(splan->mergeSourceTargetList);
+
+					splan->mergeTargetRelation += rtoffset;
+
+					foreach(l, splan->mergeActionList)
+					{
+						MergeAction *action = (MergeAction *) lfirst(l);
+
+						/* Fix targetList of each action. */
+						action->targetList = fix_join_expr(root,
+								action->targetList,
+								NULL, itlist,
+								linitial_int(splan->resultRelations),
+								rtoffset);
+
+						/* Fix quals too. */
+						action->qual = (Node *) fix_join_expr(root,
+								(List *) action->qual,
+								NULL, itlist,
+								linitial_int(splan->resultRelations),
+								rtoffset);
+					}
+				}
+
 				splan->nominalRelation += rtoffset;
 				splan->exclRelRTI += rtoffset;