add basic db maintenance tips

docs/admin/database_maintenance.md

@@ -0,0 +1,35 @@
+# Database Maintenance
+
+Regardless of whether you choose to run GoToSocial with SQLite or Postgres, you may need to occasionally take maintenance steps to keep your database running well.
+
+## SQLite
+
+### Analyze / Optimize
+
+Following [SQLite best practice](https://sqlite.org/lang_analyze.html#recommended_usage_pattern), GoToSocial runs the `optimize` SQLite pragma with `analysis_limit=1000` on closing database connections to keep index information up to date.
+
+After each database migration, GoToSocial will also run `ANALYZE` with `analysis_limit=10000` to ensure that any indexes added or removed by migrations are taken into account.
+
+As such, in normal circumstances, you should not need to run manual `ANALYZE` commands against your SQLite database file.
+
+However, if you interrupted a previous `ANALYZE` command, it could be the case that query optimizer data stored in SQLite's internal tables has been removed, and you notice that queries are running remarkably slowly.
+
+If this is the case, you can try manually running an `ANALYZE` command in the SQLite CLI tool, by entering: `PRAGMA analysis_limit=10000; ANALYZE;`.
+
+It is not necessary to run a full analyze, an approximate analyze will do. [See here](https://sqlite.org/lang_analyze.html#approximate_analyze_for_large_databases) for more info.
+
+### Vacuum
+
+GoToSocial does not currently enable auto-vacuum for SQLite. As such, you may want to periodically (eg., every few months) run a `VACUUM` command on your SQLite database, to repack the database file to an optimal size.
+
+You can see lots of information about the `VACUUM` command [here](https://sqlite.org/lang_vacuum.html).
+
+The basic steps are:
+
+1. Stop GoToSocial.
+2. Run `VACUUM` using the SQLite CLI tool (this may take quite a few minutes depending on the size of your database file).
+3. Start GoToSocial.
+
+## Postgres
+
+TODO: Maintenance recommendations for Postgres. 

mkdocs.yml

@@ -119,6 +119,7 @@ nav:
       - "admin/backup_and_restore.md"
       - "admin/media_caching.md"
       - "admin/spam.md"
+      - "admin/database_maintenance.md"
   - "Federation":
       - "federation/index.md"
       - "federation/glossary.md"