expression: fix fraction part handle of current_timestamp (pingcap#7355…

…) (pingcap#7467)

executor/executor_test.go

@@ -2833,3 +2833,37 @@ func (s *testSuite) TestIndexJoinTableDualPanic(c *C) {
 	tk.MustQuery("select a.* from a inner join (select 1 as k1,'k2-1' as k2) as k on a.f1=k.k1;").
 		Check(testkit.Rows("1 a"))
 }
+
+func (s *testSuite) TestCurrentTimestampValueSelection(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t,t1")
+
+	tk.MustExec("create table t (id int, t0 timestamp null default current_timestamp, t1 timestamp(1) null default current_timestamp(1), t2 timestamp(2) null default current_timestamp(2) on update current_timestamp(2))")
+	tk.MustExec("insert into t (id) values (1)")
+	rs := tk.MustQuery("select t0, t1, t2 from t where id = 1")
+	t0 := rs.Rows()[0][0].(string)
+	t1 := rs.Rows()[0][1].(string)
+	t2 := rs.Rows()[0][2].(string)
+	c.Assert(len(strings.Split(t0, ".")), Equals, 1)
+	c.Assert(len(strings.Split(t1, ".")[1]), Equals, 1)
+	c.Assert(len(strings.Split(t2, ".")[1]), Equals, 2)
+	tk.MustQuery("select id from t where t0 = ?", t0).Check(testkit.Rows("1"))
+	tk.MustQuery("select id from t where t1 = ?", t1).Check(testkit.Rows("1"))
+	tk.MustQuery("select id from t where t2 = ?", t2).Check(testkit.Rows("1"))
+	time.Sleep(time.Second / 2)
+	tk.MustExec("update t set t0 = now() where id = 1")
+	rs = tk.MustQuery("select t2 from t where id = 1")
+	newT2 := rs.Rows()[0][0].(string)
+	c.Assert(newT2 != t2, IsTrue)
+
+	tk.MustExec("create table t1 (id int, a timestamp, b timestamp(2), c timestamp(3))")
+	tk.MustExec("insert into t1 (id, a, b, c) values (1, current_timestamp(2), current_timestamp, current_timestamp(3))")
+	rs = tk.MustQuery("select a, b, c from t1 where id = 1")
+	a := rs.Rows()[0][0].(string)
+	b := rs.Rows()[0][1].(string)
+	d := rs.Rows()[0][2].(string)
+	c.Assert(len(strings.Split(a, ".")), Equals, 1)
+	c.Assert(strings.Split(b, ".")[1], Equals, "00")
+	c.Assert(len(strings.Split(d, ".")[1]), Equals, 3)
+}

expression/helper.go

@@ -14,6 +14,7 @@
 package expression
 
 import (
+	"math"
 	"strings"
 	"time"
 
@@ -57,7 +58,7 @@ func GetTimeValue(ctx sessionctx.Context, v interface{}, tp byte, fsp int) (d ty
 	case string:
 		upperX := strings.ToUpper(x)
 		if upperX == strings.ToUpper(ast.CurrentTimestamp) {
-			value.Time = types.FromGoTime(defaultTime)
+			value.Time = types.FromGoTime(defaultTime.Truncate(time.Duration(math.Pow10(9-fsp)) * time.Nanosecond))
 			if tp == mysql.TypeTimestamp {
 				err = value.ConvertTimeZone(time.Local, ctx.GetSessionVars().GetTimeZone())
 				if err != nil {