diff --git a/src/backend/distributed/planner/insert_select_planner.c b/src/backend/distributed/planner/insert_select_planner.c
index 3bf0bb327..60d774d01 100644
--- a/src/backend/distributed/planner/insert_select_planner.c
+++ b/src/backend/distributed/planner/insert_select_planner.c
@@ -1404,6 +1404,7 @@ InsertPartitionColumnMatchesSelect(Query *query, RangeTblEntry *insertRte,
 		/* we can set the select relation id */
 		*selectPartitionColumnTableId = subqueryPartitionColumnRelationId;
 
+
 		break;
 	}
 
diff --git a/src/backend/distributed/planner/multi_logical_optimizer.c b/src/backend/distributed/planner/multi_logical_optimizer.c
index c4c11f4eb..de5367916 100644
--- a/src/backend/distributed/planner/multi_logical_optimizer.c
+++ b/src/backend/distributed/planner/multi_logical_optimizer.c
@@ -4557,6 +4557,31 @@ FindReferencedTableColumn(Expr *columnExpression, List *parentQueryList, Query *
 		FindReferencedTableColumn(joinColumn, parentQueryList, query, column,
 								  rteContainingReferencedColumn, skipOuterVars);
 	}
+#if PG_VERSION_NUM >= 180000
+	else if (rangeTableEntry->rtekind == RTE_GROUP)
+	{
+		/*
+		 * PG 18: synthetic GROUP RTE.  Each groupexprs item corresponds to the
+		 * columns produced by the grouping step, in the *same ordinal order* as
+		 * the Vars that reference them.
+		 */
+		List *groupexprs = rangeTableEntry->groupexprs;
+		AttrNumber groupIndex = candidateColumn->varattno - 1;
+
+		/* Safety check */
+		if (groupIndex < 0 || groupIndex >= list_length(groupexprs))
+		{
+			return;  /* malformed Var */
+		}
+		Expr *groupExpr = (Expr *) list_nth(groupexprs, groupIndex);
+
+		/* Recurse on the underlying expression (stay in the same query) */
+		FindReferencedTableColumn(groupExpr, parentQueryList, query,
+								  column, rteContainingReferencedColumn,
+								  skipOuterVars);
+	}
+#endif   /* PG_VERSION_NUM >= 180000 */
+
 	else if (rangeTableEntry->rtekind == RTE_CTE)
 	{
 		/*
diff --git a/src/backend/distributed/planner/multi_logical_planner.c b/src/backend/distributed/planner/multi_logical_planner.c
index d1e2e6bca..55f1eec2a 100644
--- a/src/backend/distributed/planner/multi_logical_planner.c
+++ b/src/backend/distributed/planner/multi_logical_planner.c
@@ -136,6 +136,9 @@ static MultiNode * ApplyCartesianProductReferenceJoin(MultiNode *leftNode,
 static MultiNode * ApplyCartesianProduct(MultiNode *leftNode, MultiNode *rightNode,
 										 List *partitionColumnList, JoinType joinType,
 										 List *joinClauses);
+#if PG_VERSION_NUM >= PG_VERSION_18
+static bool ExprMentionsPartitionColumn(Node *node, Query *query);
+#endif
 
 
 /*
@@ -224,9 +227,21 @@ TargetListOnPartitionColumn(Query *query, List *targetEntryList)
 		TargetEntry *targetEntry = (TargetEntry *) lfirst(targetEntryCell);
 		Expr *targetExpression = targetEntry->expr;
 
-		bool skipOuterVars = true;
-		bool isPartitionColumn = IsPartitionColumn(targetExpression, query,
-												   skipOuterVars);
+		bool isPartitionColumn;
+		bool skipOuterVars = false;
+
+#if PG_VERSION_NUM >= PG_VERSION_18
+		isPartitionColumn =
+			ExprMentionsPartitionColumn((Node *) targetExpression, query);
+#else
+		{
+			skipOuterVars = true;
+			isPartitionColumn =
+				IsPartitionColumn(targetExpression, query, skipOuterVars);
+		}
+#endif
+
+
 		Var *column = NULL;
 		RangeTblEntry *rte = NULL;
 
@@ -292,6 +307,79 @@ TargetListOnPartitionColumn(Query *query, List *targetEntryList)
 }
 
 
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+/*
+ * ExprMentionsPartitionColumn
+ *
+ * Return true iff `node` ultimately resolves to the partition column of
+ * *any* distributed table referenced by `query`.
+ *
+ *  • Understands OUTER_VAR indirection (PG ≥ 17)
+ *  • Understands synthetic RTE_GROUP entries (PG ≥ 18)
+ *  • Falls back to original logic for PG 15/16 automatically
+ */
+static bool
+ExprMentionsPartitionColumn(Node *node, Query *query)
+{
+	if (node == NULL)
+	{
+		return false;
+	}
+
+	if (IsA(node, Var))
+	{
+		Var *v = (Var *) node;
+
+		/* Follow OUTER_VAR → target-list indirection, if present */
+		if (v->varno == OUTER_VAR)
+		{
+			TargetEntry *tle = get_tle_by_resno(query->targetList, v->varattno);
+			return tle && ExprMentionsPartitionColumn((Node *) tle->expr, query);
+		}
+
+		/* Sanity-check varno */
+		if (v->varno <= 0 || v->varno > list_length(query->rtable))
+		{
+			return false;
+		}
+
+		RangeTblEntry *rte = rt_fetch(v->varno, query->rtable);
+
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+		/* Synthetic GROUP RTE – examine its expressions instead */
+		if (rte->rtekind == RTE_GROUP && rte->groupexprs)
+		{
+			ListCell *lc;
+			foreach(lc, rte->groupexprs)
+			if (ExprMentionsPartitionColumn((Node *) lfirst(lc), query))
+			{
+				return true;
+			}
+			return false;
+		}
+#endif
+
+		/* Real table? — compare against its dist key */
+		if (rte->rtekind == RTE_RELATION && HasDistributionKey(rte->relid))
+		{
+			Var *partcol = DistPartitionKey(rte->relid);
+			return partcol && partcol->varattno == v->varattno;
+		}
+		return false;
+	}
+
+	/* Recurse through any other node type */
+	return expression_tree_walker(node,
+								  ExprMentionsPartitionColumn,
+								  (void *) query);
+}
+
+
+#endif
+
+
 /*
  * FindNodeMatchingCheckFunctionInRangeTableList finds a node for which the checker
  * function returns true.