Merge pull request #207 from krig/postgresql-import-docs

Document the Import Backups screen for Postgres databases

docs/databases/postgresql.md

@@ -15,4 +15,35 @@ PostgreSQL, often simply "Postgres", uses and extends the SQL language combined
 ## Links
 
 - [The official website ›](https://www.postgresql.org/)
-- [GitHub ›](https://github.com/postgres/postgres)
+- [GitHub ›](https://github.com/postgres/postgres)
+
+## Import Backups
+
+Coolify can import a database dump into a running PostgreSQL instance using the
+**Import Backups** section of the Configuration for the instance.
+
+The database dump can either be a file uploaded to the server, or dragged and
+dropped into the Configuration screen directly.
+
+The import command can be customized, but by default it expects a database dump
+created using the `pg_dump` command with the `-Fc` flag passed in (custom
+format).
+
+For example, the following command connects to a PostgreSQL database running in
+a local Docker container named `pg-db` as the database user `postgres` and
+writes a dump of the `postgres` database to the file `example-database.sql.gz`:
+
+```bash
+docker exec pg-db pg_dump -U postgres -d postgres -Fc >example-database.sql.gz
+```
+
+### Note on upgrading PostgreSQL
+
+The __custom__ dump format is sensitive to version differences between the dump and
+restore commands.
+
+Use the plain (default) or __tar__ dump formats to migrate from an older version
+of PostgreSQL to a newer version. When using plain format dumps, use `psql` as
+the custom import command instead of `pg_restore`.
+
+See the PostgreSQL documentation for `pg_dump` and `pg_restore` for more information.