Improve performance of row level security policies Using constraint_column_usage instead of key_column_usage makes the query twice as fast. I did not explore why. Let's just take it. Using 'EXISTS(... WHERE ... = value) is often more efficient than value IN(...) since it allows the inner query to be executed only up to the point where it turns out to return more than nothing with filtering directly in place.

The gemma database schema requires PostgreSQL >= 11.

`dot.tmpl` is a template file for `postgresql_autodoc`
to be more similiar to UML and leave out some less useful labels.

See  `../docker/README.md`