executor: fix wrong default zero value for year type (#20824) (#20829)

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

executor/insert_test.go

@@ -1252,3 +1252,19 @@ func (s *testSuite9) TestInsertRuntimeStat(c *C) {
 	stats.Merge(stats.Clone())
 	c.Assert(stats.String(), Equals, "prepare:6s, check_insert:{total_time:4s, mem_insert_time:2s, prefetch:2s}")
 }
+
+func (s *testSuite9) TestIssue20768(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1, t2")
+	tk.MustExec("create table t1(a year, primary key(a))")
+	tk.MustExec("insert ignore into t1 values(null)")
+	tk.MustExec("create table t2(a int, key(a))")
+	tk.MustExec("insert into t2 values(0)")
+	tk.MustQuery("select /*+ hash_join(t1) */ * from t1 join t2 on t1.a = t2.a").Check(testkit.Rows("0 0"))
+	tk.MustQuery("select /*+ inl_join(t1) */ * from t1 join t2 on t1.a = t2.a").Check(testkit.Rows("0 0"))
+	tk.MustQuery("select /*+ inl_join(t2) */ * from t1 join t2 on t1.a = t2.a").Check(testkit.Rows("0 0"))
+	tk.MustQuery("select /*+ inl_hash_join(t1) */ * from t1 join t2 on t1.a = t2.a").Check(testkit.Rows("0 0"))
+	tk.MustQuery("select /*+ inl_merge_join(t1) */ * from t1 join t2 on t1.a = t2.a").Check(testkit.Rows("0 0"))
+	tk.MustQuery("select /*+ merge_join(t1) */ * from t1 join t2 on t1.a = t2.a").Check(testkit.Rows("0 0"))
+}

table/column.go

@@ -501,12 +501,14 @@ func getColDefaultValueFromNil(ctx sessionctx.Context, col *model.ColumnInfo) (t
 func GetZeroValue(col *model.ColumnInfo) types.Datum {
 	var d types.Datum
 	switch col.Tp {
-	case mysql.TypeTiny, mysql.TypeInt24, mysql.TypeShort, mysql.TypeLong, mysql.TypeLonglong, mysql.TypeYear:
+	case mysql.TypeTiny, mysql.TypeInt24, mysql.TypeShort, mysql.TypeLong, mysql.TypeLonglong:
 		if mysql.HasUnsignedFlag(col.Flag) {
 			d.SetUint64(0)
 		} else {
 			d.SetInt64(0)
 		}
+	case mysql.TypeYear:
+		d.SetInt64(0)
 	case mysql.TypeFloat:
 		d.SetFloat32(0)
 	case mysql.TypeDouble: