planner: revise isnullRejected check for And and OR

expression/constant_fold.go

@@ -181,6 +181,11 @@ func foldConstant(expr Expression) (Expression, bool) {
 			if !hasNullArg || !sc.InNullRejectCheck || x.FuncName.L == ast.NullEQ {
 				return expr, isDeferredConst
 			}
+			// For `AND` and `OR`, if any of the arguments is null and not all arguments are constant, then it is unFoldAble.
+			switch x.FuncName.L {
+			case ast.LogicAnd, ast.LogicOr:
+				return expr, isDeferredConst
+			}
 			constArgs := make([]Expression, len(args))
 			for i, arg := range args {
 				if argIsConst[i] {

planner/core/plan_test.go

@@ -1076,3 +1076,20 @@ func TestNullEQConditionPlan(t *testing.T) {
 			{"Point_Get_5", "root", "handle:0"},
 		})
 }
+
+// https://github.com/pingcap/tidb/issues/38304
+func TestOuterJoinOnNull(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("CREATE TABLE t0(c0 BLOB(5), c1 BLOB(5));")
+	tk.MustExec("CREATE TABLE t1 (c0 BOOL);")
+	tk.MustExec("INSERT INTO t1 VALUES(false);")
+	tk.MustExec("")
+	tk.MustExec("INSERT INTO t0(c0, c1) VALUES ('>', true);")
+	tk.MustQuery("SELECT * FROM t0 LEFT OUTER JOIN t1 ON NULL; ").Check(testkit.Rows("> 1 <nil>"))
+	tk.MustQuery("SELECT NOT '2' =(t1.c0 AND t0.c1 IS NULL) FROM t0 LEFT OUTER JOIN t1 ON NULL; ").Check(testkit.Rows("1"))
+	tk.MustQuery("SELECT * FROM t0 LEFT JOIN t1 ON NULL WHERE NOT '2' =(t1.c0 AND t0.c1 IS NULL); ").Check(testkit.Rows("> 1 <nil>"))
+	tk.MustQuery("SELECT * FROM t0 LEFT JOIN t1 ON NULL WHERE t1.c0 or true; ").Check(testkit.Rows("> 1 <nil>"))
+	tk.MustQuery("SELECT * FROM t0 LEFT JOIN t1 ON NULL WHERE not(t1.c0 and false); ").Check(testkit.Rows("> 1 <nil>"))
+}