Merge pull request #33691 from tgxworld/add_config_to_disable_advisory_locks

Add database configuration to disable advisory locks.

activerecord/CHANGELOG.md

@@ -1,3 +1,13 @@
+*   Add database configuration to disable advisory locks.
+
+    ```
+    production:
+      adapter: postgresql
+      advisory_locks: false
+    ```
+
+    *Guo Xiang*
+
 *   SQLite3 adapter `alter_table` method restores foreign keys.
 
     *Yasuo Honda*

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -77,7 +77,14 @@ class AbstractAdapter
       SIMPLE_INT = /\A\d+\z/
 
       attr_accessor :visitor, :pool
-      attr_reader :schema_cache, :owner, :logger, :prepared_statements, :lock
+
+      attr_reader :schema_cache,
+                  :owner,
+                  :logger,
+                  :prepared_statements,
+                  :lock,
+                  :advisory_locks
+
       alias :in_use? :owner
 
       def self.type_cast_config_to_integer(config)
@@ -119,6 +126,10 @@ def initialize(connection, logger = nil, config = {}) # :nodoc:
         else
           @prepared_statements = false
         end
+
+        @advisory_locks_enabled = self.class.type_cast_config_to_boolean(
+          config.fetch(:advisory_locks, true)
+        )
       end
 
       def migrations_paths # :nodoc:

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -111,7 +111,7 @@ def supports_virtual_columns?
       end
 
       def supports_advisory_locks?
-        true
+        @advisory_locks_enabled
       end
 
       def get_advisory_lock(lock_name, timeout = 0) # :nodoc:

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -298,7 +298,7 @@ def supports_ddl_transactions?
       end
 
       def supports_advisory_locks?
-        true
+        @advisory_locks_enabled
       end
 
       def supports_explain?

activerecord/test/cases/adapters/helpers/test_supports_advisory_locks.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require "support/connection_helper"
+
+module TestSupportsAdvisoryLocks
+  include ConnectionHelper
+
+  def test_supports_advisory_locks?
+    assert ActiveRecord::Base.connection.supports_advisory_locks?
+
+    run_without_connection do |orig_connection|
+      ActiveRecord::Base.establish_connection(
+        orig_connection.merge(advisory_locks: false)
+      )
+
+      assert_not ActiveRecord::Base.connection.supports_advisory_locks?
+
+      ActiveRecord::Base.establish_connection(
+        orig_connection.merge(advisory_locks: true)
+      )
+
+      assert ActiveRecord::Base.connection.supports_advisory_locks?
+    end
+  end
+end

activerecord/test/cases/adapters/mysql2/test_advisory_locks_disabled_test.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "cases/adapters/helpers/test_supports_advisory_locks"
+
+class Mysql2AdvisoryLocksDisabledTest < ActiveRecord::Mysql2TestCase
+  include TestSupportsAdvisoryLocks
+end

activerecord/test/cases/adapters/postgresql/advisory_locks_disabled_test.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "cases/adapters/helpers/test_supports_advisory_locks"
+
+class PostgresqlAdvisoryLocksDisabledTest < ActiveRecord::PostgreSQLTestCase
+  include TestSupportsAdvisoryLocks
+end

guides/source/configuring.md

@@ -989,6 +989,14 @@ development:
 
 If your development database has a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the `development` section as appropriate.
 
+Advisory Locks are enabled by default on MySQL and are used to make database migrations concurrent safe. You can disable advisory locks by setting `advisory_locks` to `false`:
+
+```yaml
+production:
+  adapter: mysql2
+  advisory_locks: false
+```
+
 #### Configuring a PostgreSQL Database
 
 If you choose to use PostgreSQL, your `config/database.yml` will be customized to use PostgreSQL databases:
@@ -1001,12 +1009,13 @@ development:
   pool: 5
 ```
 
-Prepared Statements are enabled by default on PostgreSQL. You can disable prepared statements by setting `prepared_statements` to `false`:
+By default Active Record uses database features like prepared statements and advisory locks. You might need to disable those features if you're using an external connection pooler like PgBouncer:
 
 ```yaml
 production:
   adapter: postgresql
   prepared_statements: false
+  advisory_locks: false
 ```
 
 If enabled, Active Record will create up to `1000` prepared statements per database connection by default. To modify this behavior you can set `statement_limit` to a different value: