1 files changed, 80 insertions, 0 deletions
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 8230cbea3c3..e7cb3fede66 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -1214,6 +1214,86 @@ inline_cte_walker(Node *node, inline_cte_walker_context *context)
 	return expression_tree_walker(node, inline_cte_walker, context);
 }
 
+/*
+ * Attempt to transform 'testexpr' over the VALUES subquery into
+ * a ScalarArrayOpExpr.  We currently support the transformation only when
+ * it ends up with a constant array.  Otherwise, the evaluation of non-hashed
+ * SAOP might be slower than the corresponding Hash Join with VALUES.
+ *
+ * Return transformed ScalarArrayOpExpr or NULL if transformation isn't
+ * allowed.
+ */
+ScalarArrayOpExpr *
+convert_VALUES_to_ANY(PlannerInfo *root, Node *testexpr, Query *values)
+{
+	RangeTblEntry *rte;
+	Node	   *leftop;
+	Node	   *rightop;
+	Oid			opno;
+	ListCell   *lc;
+	Oid			inputcollid;
+	List	   *exprs = NIL;
+
+	/*
+	 * Check we have a binary operator over a single-column subquery with no
+	 * joins and no LIMIT/OFFSET/ORDER BY clauses.
+	 */
+	if (!IsA(testexpr, OpExpr) ||
+		list_length(((OpExpr *) testexpr)->args) != 2 ||
+		list_length(values->targetList) > 1 ||
+		values->limitCount != NULL ||
+		values->limitOffset != NULL ||
+		values->sortClause != NIL ||
+		list_length(values->rtable) != 1)
+		return NULL;
+
+	rte = linitial_node(RangeTblEntry, values->rtable);
+	leftop = linitial(((OpExpr *) testexpr)->args);
+	rightop = lsecond(((OpExpr *) testexpr)->args);
+	opno = ((OpExpr *) testexpr)->opno;
+	inputcollid = ((OpExpr *) testexpr)->inputcollid;
+
+	/*
+	 * Also, check that only RTE corresponds to VALUES; the list of values has
+	 * at least two items and no volatile functions.
+	 */
+	if (rte->rtekind != RTE_VALUES ||
+		list_length(rte->values_lists) < 2 ||
+		contain_volatile_functions((Node *) rte->values_lists))
+		return NULL;
+
+	foreach(lc, rte->values_lists)
+	{
+		List	   *elem = lfirst(lc);
+		Node	   *value = linitial(elem);
+
+		/*
+		 * Prepare an evaluation of the right side of the operator with
+		 * substitution of the given value.
+		 */
+		value = convert_testexpr(root, rightop, list_make1(value));
+
+		/*
+		 * Try to evaluate constant expressions.  We could get Const as a
+		 * result.
+		 */
+		value = eval_const_expressions(root, value);
+
+		/*
+		 * As we only support constant output arrays, all the items must also
+		 * be constant.
+		 */
+		if (!IsA(value, Const))
+			return NULL;
+
+		exprs = lappend(exprs, value);
+	}
+
+	/* Finally, build ScalarArrayOpExpr at the top of the 'exprs' list. */
+	return make_SAOP_expr(opno, leftop, exprType(rightop),
+						  linitial_oid(rte->colcollations), inputcollid,
+						  exprs, false);
+}
 
 /*
  * convert_ANY_sublink_to_join: try to convert an ANY SubLink to a join