fix: postgres/mysql engine cache was not being used, fixes #12636 (#12642)

devenv/datasources.yaml

@@ -63,7 +63,8 @@ datasources:
     url: localhost:5432
     database: grafana
     user: grafana
-    password: password
+    secureJsonData:
+      password: password
     jsonData:
       sslmode: "disable"
 
@@ -74,3 +75,4 @@ datasources:
       authType: credentials
       defaultRegion: eu-west-2
 
+

pkg/tsdb/sql_engine.go

@@ -68,6 +68,7 @@ func (e *DefaultSqlEngine) InitEngine(driverName string, dsInfo *models.DataSour
 	engine.SetMaxOpenConns(10)
 	engine.SetMaxIdleConns(10)
 
+	engineCache.versions[dsInfo.Id] = dsInfo.Version
 	engineCache.cache[dsInfo.Id] = engine
 	e.XormEngine = engine