Allow separate database env variables per-connection

This commit adds a feature which allows separate database ENV variables
to be defined for each spec in a 3-tier config. The names for the
environment variables will be `#{name.upcase}_DATABASE_URL`

This commit also introduces a change in behavior around handling of
`DATABASE_URL`. Instead of using `DATABASE_URL` to change _all_ specs
in a multi-database configuration, it will now only affect the `primary`
connection.

1 files changed, 8 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/database_configurations.rb b/activerecord/lib/active_record/database_configurations.rb
index 8baa0f5af6..db76cc8a7e 100644
--- a/activerecord/lib/active_record/database_configurations.rb
+++ b/activerecord/lib/active_record/database_configurations.rb
@@ -168,12 +168,19 @@ module ActiveRecord
       end
 
       def environment_url_config(env, spec_name, config)
-        url = ENV["DATABASE_URL"]
+        url = environment_value_for(spec_name)
         return unless url
 
         ActiveRecord::DatabaseConfigurations::UrlConfig.new(env, spec_name, url, config)
       end
 
+      def environment_value_for(spec_name)
+        spec_env_key = "#{spec_name.upcase}_DATABASE_URL"
+        url = ENV[spec_env_key]
+        url ||= ENV["DATABASE_URL"] if spec_name == "primary"
+        url
+      end
+
       def method_missing(method, *args, &blk)
         case method
         when :each, :first