*: fix invalid query result on a cached table

Signed-off-by: Weizhen Wang <wangweizhen@pingcap.com>

pkg/planner/core/casetest/hint/hint_test.go

@@ -372,3 +372,12 @@ func TestHints(t *testing.T) {
 		tk.MustQuery("show warnings").Check(testkit.Rows(output[i].Warn...))
 	}
 }
+
+func TestIssue52755(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("CREATE TABLE t1 (c1 int, c2 int, UNIQUE i1 (c1, c2));")
+	tk.MustExec("INSERT INTO t1 VALUES (7, null),(5,1);")
+	tk.MustQuery("SELECT c1 FROM t1 WHERE ('m' = ALL (SELECT /*+ IGNORE_INDEX(t1, i1) */ c2 FROM t1)) IS NOT UNKNOWN; ").Check(testkit.Rows("5", "7"))
+}