document postgres min time interval

docs/sources/administration/provisioning.md

@@ -154,7 +154,7 @@ Since not all datasources have the same configuration settings we only have the
 | tlsAuthWithCACert | boolean | *All* | Enable TLS authentication using CA cert |
 | tlsSkipVerify | boolean | *All* | Controls whether a client verifies the server's certificate chain and host name. |
 | graphiteVersion | string | Graphite |  Graphite version  |
-| timeInterval | string | Elastic, InfluxDB & Prometheus | Lowest interval/step value that should be used for this data source |
+| timeInterval | string | Elastic, InfluxDB, PostgreSQL & Prometheus | Lowest interval/step value that should be used for this data source |
 | esVersion | number | Elastic | Elasticsearch version as a number (2/5/56) |
 | timeField | string | Elastic | Which field that should be used as timestamp |
 | interval | string | Elastic | Index date time format |

docs/sources/features/datasources/postgres.md

@@ -34,6 +34,21 @@ Name | Description
 *Version* | This option determines which functions are available in the query builder (only available in Grafana 5.3+).
 *TimescaleDB* | TimescaleDB is a time-series database built as a PostgreSQL extension. If enabled, Grafana will use `time_bucket` in the `$__timeGroup` macro and display TimescaleDB specific aggregate functions in the query builder (only available in Grafana 5.3+).
 
+### Min time interval
+A lower limit for the `$__interval` variable. Recommended to be set to write frequency, for example `1m` if your data is written every minute.
+This option can also be overridden/configured in a dashboard panel under data source options. It's important to note that this value **needs** to be formatted as a
+number followed by a valid time identifier, e.g. `1m` (1 minute) or `30s` (30 seconds). The following time identifiers are supported:
+
+Identifier | Description
+------------ | -------------
+`y`   | year
+`M`   | month
+`w`   | week
+`d`   | day
+`h`   | hour
+`m`   | minute
+`s`   | second
+`ms`  | millisecond
 
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