InfluxDB: fix numeric aliases in queries (#41531)

* influxdb: alerting: handle out-of-range numeric aliases

* influxdb: updated documentation

docs/sources/datasources/influxdb/_index.md

@@ -120,6 +120,7 @@ You can switch to raw query mode by clicking hamburger icon and then `Switch edi
 
 - $m = replaced with measurement name
 - $measurement = replaced with measurement name
+- $1 - $9 = replaced with part of measurement name (if you separate your measurement name with dots)
 - $col = replaced with column name
 - $tag_exampletag = replaced with the value of the `exampletag` tag. The syntax is `$tag*yourTagName`(must start with`$tag*`). To use your tag as an alias in the ALIAS BY field then the tag must be used to group by in the query.
 - You can also use [[tag_hostname]] pattern replacement syntax. For example, in the ALIAS BY field using this text `Host: [[tag_hostname]]` would substitute in the `hostname` tag value for each legend value and an example legend value would be: `Host: server1`.

pkg/tsdb/influxdb/response_parser.go

@@ -113,7 +113,7 @@ func formatFrameName(row Row, column string, query *Query) string {
 		}
 
 		pos, err := strconv.Atoi(aliasFormat)
-		if err == nil && len(nameSegment) >= pos {
+		if err == nil && len(nameSegment) > pos {
 			return []byte(nameSegment[pos])
 		}
 

pkg/tsdb/influxdb/response_parser_test.go

@@ -293,6 +293,16 @@ func TestInfluxdbResponseParser(t *testing.T) {
 				t.Errorf("Result mismatch (-want +got):\n%s", diff)
 			}
 
+			query = &Query{Alias: "alias $0 $1 $2 $3 $4"}
+			result = parser.Parse(prepare(response), query)
+			frame = result.Responses["A"]
+			name = "alias cpu upc $2 $3 $4"
+			testFrame.Name = name
+			testFrame.Fields[1].Config.DisplayNameFromDS = name
+			if diff := cmp.Diff(testFrame, frame.Frames[0], data.FrameTestCompareOptions()...); diff != "" {
+				t.Errorf("Result mismatch (-want +got):\n%s", diff)
+			}
+
 			query = &Query{Alias: "alias $1"}
 			result = parser.Parse(prepare(response), query)
 			frame = result.Responses["A"]