[mysql] fix $__timeGroup rounding (#12469)

* fix $__timeGroup rounding for mysql

* revert accidentally commented out line

pkg/tsdb/mysql/macros.go

@@ -103,7 +103,7 @@ func (m *MySqlMacroEngine) evaluateMacro(name string, args []string) (string, er
 				m.Query.Model.Set("fillValue", floatVal)
 			}
 		}
-		return fmt.Sprintf("cast(cast(UNIX_TIMESTAMP(%s)/(%.0f) as signed)*%.0f as signed)", args[0], interval.Seconds(), interval.Seconds()), nil
+		return fmt.Sprintf("UNIX_TIMESTAMP(%s) DIV %.0f * %.0f", args[0], interval.Seconds(), interval.Seconds()), nil
 	case "__unixEpochFilter":
 		if len(args) == 0 {
 			return "", fmt.Errorf("missing time column argument for macro %v", name)

pkg/tsdb/mysql/macros_test.go

@@ -39,7 +39,7 @@ func TestMacroEngine(t *testing.T) {
 				sql, err := engine.Interpolate(query, timeRange, "GROUP BY $__timeGroup(time_column,'5m')")
 				So(err, ShouldBeNil)
 
-				So(sql, ShouldEqual, "GROUP BY cast(cast(UNIX_TIMESTAMP(time_column)/(300) as signed)*300 as signed)")
+				So(sql, ShouldEqual, "GROUP BY UNIX_TIMESTAMP(time_column) DIV 300 * 300")
 			})
 
 			Convey("interpolate __timeGroup function with spaces around arguments", func() {
@@ -47,7 +47,7 @@ func TestMacroEngine(t *testing.T) {
 				sql, err := engine.Interpolate(query, timeRange, "GROUP BY $__timeGroup(time_column , '5m')")
 				So(err, ShouldBeNil)
 
-				So(sql, ShouldEqual, "GROUP BY cast(cast(UNIX_TIMESTAMP(time_column)/(300) as signed)*300 as signed)")
+				So(sql, ShouldEqual, "GROUP BY UNIX_TIMESTAMP(time_column) DIV 300 * 300")
 			})
 
 			Convey("interpolate __timeFilter function", func() {

pkg/tsdb/mysql/mysql_test.go

@@ -209,11 +209,12 @@ func TestMySQL(t *testing.T) {
 				So(queryResult.Error, ShouldBeNil)
 
 				points := queryResult.Series[0].Points
-				So(len(points), ShouldEqual, 6)
+				// without fill this should result in 4 buckets
+				So(len(points), ShouldEqual, 4)
 
 				dt := fromStart
 
-				for i := 0; i < 3; i++ {
+				for i := 0; i < 2; i++ {
 					aValue := points[i][0].Float64
 					aTime := time.Unix(int64(points[i][1].Float64)/1000, 0)
 					So(aValue, ShouldEqual, 15)
@@ -221,9 +222,9 @@ func TestMySQL(t *testing.T) {
 					dt = dt.Add(5 * time.Minute)
 				}
 
-				// adjust for 5 minute gap
-				dt = dt.Add(5 * time.Minute)
-				for i := 3; i < 6; i++ {
+				// adjust for 10 minute gap between first and second set of points
+				dt = dt.Add(10 * time.Minute)
+				for i := 2; i < 4; i++ {
 					aValue := points[i][0].Float64
 					aTime := time.Unix(int64(points[i][1].Float64)/1000, 0)
 					So(aValue, ShouldEqual, 20)
@@ -259,7 +260,7 @@ func TestMySQL(t *testing.T) {
 
 				dt := fromStart
 
-				for i := 0; i < 3; i++ {
+				for i := 0; i < 2; i++ {
 					aValue := points[i][0].Float64
 					aTime := time.Unix(int64(points[i][1].Float64)/1000, 0)
 					So(aValue, ShouldEqual, 15)
@@ -267,17 +268,23 @@ func TestMySQL(t *testing.T) {
 					dt = dt.Add(5 * time.Minute)
 				}
 
+				// check for NULL values inserted by fill
+				So(points[2][0].Valid, ShouldBeFalse)
 				So(points[3][0].Valid, ShouldBeFalse)
 
-				// adjust for 5 minute gap
-				dt = dt.Add(5 * time.Minute)
-				for i := 4; i < 7; i++ {
+				// adjust for 10 minute gap between first and second set of points
+				dt = dt.Add(10 * time.Minute)
+				for i := 4; i < 6; i++ {
 					aValue := points[i][0].Float64
 					aTime := time.Unix(int64(points[i][1].Float64)/1000, 0)
 					So(aValue, ShouldEqual, 20)
 					So(aTime, ShouldEqual, dt)
 					dt = dt.Add(5 * time.Minute)
 				}
+
+				// check for NULL values inserted by fill
+				So(points[6][0].Valid, ShouldBeFalse)
+
 			})
 
 			Convey("When doing a metric query using timeGroup with float fill enabled", func() {