expression, types: fix StrToDuration result (#32896)

close #31680

expression/builtin_time_test.go

@@ -1614,6 +1614,7 @@ func TestTimeDiff(t *testing.T) {
 		{[]interface{}{"10:10:10", "10:9:0"}, "00:01:10", false, 0, 10, false},
 		{[]interface{}{"2016-12-00 12:00:00", "10:9:0"}, "", true, 0, 10, false},
 		{[]interface{}{"2016-12-00 12:00:00", ""}, "", true, 0, 10, true},
+		{[]interface{}{"00:00:00.000000", "00:00:00.000001"}, "-00:00:00.000001", false, 6, 17, false},
 	}
 
 	for _, c := range tests {

types/convert.go

@@ -315,6 +315,9 @@ func StrToDuration(sc *stmtctx.StatementContext, str string, fsp int) (d Duratio
 	if length > 0 && str[0] == '-' {
 		length--
 	}
+	if n := strings.IndexByte(str, '.'); n >= 0 {
+		length = length - len(str[n:])
+	}
 	// Timestamp format is 'YYYYMMDDHHMMSS' or 'YYMMDDHHMMSS', which length is 12.
 	// See #3923, it explains what we do here.
 	if length >= 12 {

types/convert_test.go

@@ -1212,6 +1212,8 @@ func TestStrToDuration(t *testing.T) {
 		{"20190101180000", 6, false},
 		{"20190101180000", 1, false},
 		{"20190101181234", 3, false},
+		{"00:00:00.000000", 6, true},
+		{"00:00:00", 0, true},
 	}
 	for _, tt := range tests {
 		_, _, isDuration, err := StrToDuration(sc, tt.str, tt.fsp)