Update query.go

Scenario : Initially there is no data or zero rows returned for a SQL query for a particular DB and then if we start sql_exporter . In this case, sql_exporter Metrics UI doesn't have any details to show that SQL query is executed and it is failed.

With this change, SQL Exported Metrics indicates user on SQL query is executed and it is failed.

Below is entry will come in Metrics with this code change.

sql_exporter_last_scrape_failed{database="DB",driver="postgres",host="hostNmae",query="sql_exporter_query",sql_job="sql_exporter_query",user="reader"} 1

Author: santubvb

query.go

@@ -66,6 +66,7 @@ func (q *Query) Run(conn *connection) error {
 		if q.AllowZeroRows {
 			failedScrapes.WithLabelValues(conn.driver, conn.host, conn.database, conn.user, q.jobName, q.Name).Set(0.0)
 		} else {
+			failedScrapes.WithLabelValues(conn.driver, conn.host, conn.database, conn.user, q.jobName, q.Name).Set(1.0)
 			return fmt.Errorf("zero rows returned")
 		}
 	}