grafana/public/app/plugins/datasource/postgres/README.md

Grafana PostgreSQL Data Source - Native Plugin

Grafana ships with a built-in PostgreSQL data source plugin that allows you to query and visualize data from a PostgreSQL compatible database.

Adding the data source

1. Open the side menu by clicking the Grafana icon in the top header.
2. In the side menu under the Dashboards link you should find a link named Data Sources.
3. Click the + Add data source button in the top header.
4. Select PostgreSQL from the Type dropdown.

http://docs.grafana.org/features/datasources/postgres/