planner: make a copy of column before modifying its InOperand (#19472)

executor/join_test.go

@@ -1879,6 +1879,15 @@ func (s *testSuiteJoin2) TestNullEmptyAwareSemiJoin(c *C) {
 			result.Check(results[i].result)
 		}
 	}
+
+	tk.MustExec("drop table if exists t1, t2")
+	tk.MustExec("create table t1(a int)")
+	tk.MustExec("create table t2(a int)")
+	tk.MustExec("insert into t1 values(1),(2)")
+	tk.MustExec("insert into t2 values(1),(null)")
+	tk.MustQuery("select * from t1 where a not in (select a from t2 where t1.a = t2.a)").Check(testkit.Rows(
+		"2",
+	))
 }
 
 func (s *testSuiteJoin1) TestScalarFuncNullSemiJoin(c *C) {

planner/core/expression_rewriter.go

@@ -787,12 +787,12 @@ func (er *expressionRewriter) handleInSubquery(ctx context.Context, v *ast.Patte
 		// For AntiSemiJoin/LeftOuterSemiJoin/AntiLeftOuterSemiJoin, we cannot treat `in` expression as
 		// normal column equal condition, so we specially mark the inner operand here.
 		if v.Not || asScalar {
-			rCol.InOperand = true
 			// If both input columns of `in` expression are not null, we can treat the expression
 			// as normal column equal condition instead.
-			lCol, ok := lexpr.(*expression.Column)
-			if ok && mysql.HasNotNullFlag(lCol.GetType().Flag) && mysql.HasNotNullFlag(rCol.GetType().Flag) {
-				rCol.InOperand = false
+			if !mysql.HasNotNullFlag(lexpr.GetType().Flag) || !mysql.HasNotNullFlag(rCol.GetType().Flag) {
+				rColCopy := *rCol
+				rColCopy.InOperand = true
+				rexpr = &rColCopy
 			}
 		}
 	} else {