add compatibility code to handle pre 5.3 usage

pkg/tsdb/postgres/macros.go

@@ -30,6 +30,23 @@ func (m *postgresMacroEngine) Interpolate(query *tsdb.Query, timeRange *tsdb.Tim
 	var macroError error
 
 	sql = replaceAllStringSubmatchFunc(rExp, sql, func(groups []string) string {
+
+		// detect if $__timeGroup is supposed to add AS time for pre 5.3 compatibility
+		// if there is a ',' directly after the macro call $__timeGroup is probably used
+		// in the old way. Inside window function ORDER BY $__timeGroup will be followed
+		// by ')'
+		if groups[1] == "__timeGroup" {
+			if index := strings.Index(sql, groups[0]); index >= 0 {
+				index += len(groups[0])
+				if len(sql) > index {
+					// check for character after macro expression
+					if sql[index] == ',' {
+						groups[1] = "__timeGroupAlias"
+					}
+				}
+			}
+		}
+
 		args := strings.Split(groups[2], ",")
 		for i, arg := range args {
 			args[i] = strings.Trim(arg, " ")

pkg/tsdb/postgres/macros_test.go

@@ -48,14 +48,27 @@ func TestMacroEngine(t *testing.T) {
 				So(sql, ShouldEqual, fmt.Sprintf("select '%s'", from.Format(time.RFC3339)))
 			})
 
+			Convey("interpolate __timeGroup function pre 5.3 compatibility", func() {
+
+				sql, err := engine.Interpolate(query, timeRange, "SELECT $__timeGroup(time_column,'5m'), value")
+				So(err, ShouldBeNil)
+
+				So(sql, ShouldEqual, "SELECT floor(extract(epoch from time_column)/300)*300 AS \"time\", value")
+
+				sql, err = engine.Interpolate(query, timeRange, "SELECT $__timeGroup(time_column,'5m') as time, value")
+				So(err, ShouldBeNil)
+
+				So(sql, ShouldEqual, "SELECT floor(extract(epoch from time_column)/300)*300 as time, value")
+			})
+
 			Convey("interpolate __timeGroup function", func() {
 
-				sql, err := engine.Interpolate(query, timeRange, "$__timeGroup(time_column,'5m')")
+				sql, err := engine.Interpolate(query, timeRange, "SELECT $__timeGroup(time_column,'5m')")
 				So(err, ShouldBeNil)
-				sql2, err := engine.Interpolate(query, timeRange, "$__timeGroupAlias(time_column,'5m')")
+				sql2, err := engine.Interpolate(query, timeRange, "SELECT $__timeGroupAlias(time_column,'5m')")
 				So(err, ShouldBeNil)
 
-				So(sql, ShouldEqual, "floor(extract(epoch from time_column)/300)*300")
+				So(sql, ShouldEqual, "SELECT floor(extract(epoch from time_column)/300)*300")
 				So(sql2, ShouldEqual, sql+" AS \"time\"")
 			})