Database; Remove database metric feature flag and update changelog (#28438)

* adds note about broken feature flag

* remove code to enable feature flag

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

CHANGELOG.md

@@ -56,12 +56,17 @@
 # 7.2.2 (2020-10-21)
 
 ### Features / Enhancements
-* **Instrumentation**: Add counters and histograms for database queries. [#28236](https://github.com/grafana/grafana/pull/28236), [@bergquist](https://github.com/bergquist)
-* **Instrumentation**: Add histogram for request duration. [#28364](https://github.com/grafana/grafana/pull/28364), [@bergquist](https://github.com/bergquist)
-* **Instrumentation**: Adds environment_info metric. [#28355](https://github.com/grafana/grafana/pull/28355), [@bergquist](https://github.com/bergquist)
+
+**Caution:** Please do not use/enable the `database_metrics` feature flag. It will corrupt MySQL database tables. See [#28440](https://github.com/grafana/grafana/issues/28440) for more information.
+
+~~**Instrumentation**: Add counters and histograms for database queries. [#28236](https://github.com/grafana/grafana/pull/28236), [@bergquist](https://github.com/bergquist)~~
+
+- **Instrumentation**: Add histogram for request duration. [#28364](https://github.com/grafana/grafana/pull/28364), [@bergquist](https://github.com/bergquist)
+- **Instrumentation**: Adds environment_info metric. [#28355](https://github.com/grafana/grafana/pull/28355), [@bergquist](https://github.com/bergquist)
 
 ### Bug Fixes
-* **CloudWatch**: Fix custom metrics. [#28391](https://github.com/grafana/grafana/pull/28391), [@aknuds1](https://github.com/aknuds1)
+
+- **CloudWatch**: Fix custom metrics. [#28391](https://github.com/grafana/grafana/pull/28391), [@aknuds1](https://github.com/aknuds1)
 
 # 7.2.1 (2020-10-08)
 

pkg/services/sqlstore/sqlstore.go

@@ -238,10 +238,6 @@ func (ss *SqlStore) getEngine() (*xorm.Engine, error) {
 		return nil, err
 	}
 
-	if ss.Cfg.IsDatabaseMetricsEnabled() {
-		ss.dbCfg.Type = WrapDatabaseDriverWithHooks(ss.dbCfg.Type)
-	}
-
 	sqlog.Info("Connecting to DB", "dbtype", ss.dbCfg.Type)
 	if ss.dbCfg.Type == migrator.SQLITE && strings.HasPrefix(connectionString, "file:") {
 		exists, err := fs.Exists(ss.dbCfg.Path)