influx: docs for retention policy option

docs/sources/configuration/index.md

@@ -62,6 +62,7 @@ Read [how to configure](./sql_datasource) SQL data source in Grafana.
 
 - **Enable**: enable Direct DB Connection.
 - **Data Source**: Select Data Source for Zabbix history database.
+- **Retention Policy** (InfluxDB only): Specify retention policy name for fetching long-term stored data. Grafana will fetch data from this retention policy if query time range suitable for trends query. Leave it blank if only default retention policy used.
 
 #### Supported databases
 

docs/sources/configuration/provisioning.md

@@ -34,8 +34,11 @@ datasources:
     disableReadOnlyUsersAck: true
     # Direct DB Connection options
     dbConnectionEnable: true
-    # Name of existing SQL datasource
+    # Name of existing datasource for Direct DB Connection
     dbConnectionDatasourceName: MySQL Zabbix
+    # Retention policy name (InfluxDB only) for fetching long-term stored data.
+    # Leave it blank if only default retention policy used.
+    dbConnectionRetentionPolicy: one_year
   version: 1
   editable: false