store/tikv,mysql: improve error message of GC life time

mysql/errname.go

@@ -901,7 +901,7 @@ var MySQLErrName = map[uint16]string{
 	ErrTiKVServerBusy:     "TiKV server is busy",
 	ErrResolveLockTimeout: "Resolve lock timeout",
 	ErrRegionUnavailable:  "Region is unavailable",
-	ErrGCTooEarly:         "GC life time is shorter than transaction duration",
+	ErrGCTooEarly:         "GC life time is shorter than transaction duration, transaction starts at %v, GC safe point is %v",
 
 	ErrTxnTooLarge: "Transaction is too large",
 }

store/tikv/kv.go

@@ -165,7 +165,9 @@ func (s *tikvStore) CheckVisibility(startTime uint64) error {
 	}
 
 	if startTime < cachedSafePoint {
-		return ErrGCTooEarly
+		t1 := oracle.GetTimeFromTS(startTime)
+		t2 := oracle.GetTimeFromTS(cachedSafePoint)
+		return ErrGCTooEarly.GenByArgs(t1, t2)
 	}
 
 	return nil

store/tikv/oracle/oracle.go

@@ -53,3 +53,9 @@ func GetPhysical(t time.Time) int64 {
 func EncodeTSO(ts int64) uint64 {
 	return uint64(ts) << physicalShiftBits
 }
+
+// GetTimeFromTS extracts time.Time from a timestamp.
+func GetTimeFromTS(ts uint64) time.Time {
+	ms := ExtractPhysical(ts)
+	return time.Unix(ms/1000, (ms%1000)*1e6)
+}