Add single database configuration section

README.md

@@ -96,6 +96,30 @@ If `connects_to` is set, it will be passed directly.
 
 If none of these are set, Solid Cache will use the `ActiveRecord::Base` connection pool. This means that cache reads and writes will be part of any wrapping database transaction.
 
+### Single database configuration
+
+Running Solid Cache in a separate database is recommended, but for PostgreSQL/MySQL/Trilogy you can use a single physical database and still keep separate connection pools for app and cache traffic.
+
+1. Move the schema from `db/cache_schema.rb` (or `db/cache_structure.sql`) into a normal app migration, then delete the cache schema file
+2. Keep `database: cache` in `config/cache.yml`
+3. Point `primary` and `cache` at the same database in `config/database.yml`, and disable database tasks for `cache`:
+
+```yaml
+production:
+  primary: &primary_production
+    <<: *default
+    database: app_production
+    username: app
+    password: <%= ENV["APP_DATABASE_PASSWORD"] %>
+  cache:
+    <<: *primary_production
+    database_tasks: false
+```
+
+4. Run `bin/rails db:migrate`
+
+Do not use this setup with SQLite. SQLite allows only one write transaction at a time, so separate pools to the same database can block each other. For SQLite, use a separate cache database.
+
 ### Engine configuration
 
 There are five options that can be set on the engine: