Activerecord base connection. Introduction ¶ ↑ A connection pool synchronizes thread access to a limited number of database connections. connection Database Connection Management: It manages the connection to the database for all ActiveRecord models. Apr 2, 2014 · If 2 different models will establish connection they will get into pool (establish connection in some models and then type ActiveRecord::Base. connection. Active Record – Object-relational mapping in Rails Active Record connects classes to relational database tables to establish an almost zero-configuration persistence layer for applications. But you can also set a class-specific connection. connection_pool. AdapterNotFound - The :adapter key used in ActiveRecord::Base. This can also be used to “borrow” the connection to do database work that isn’t easily done without going straight to SQL. Sep 9, 2025 · Configuring database connections in the Active Record connection pool for apps running with a multi-threaded or multi-process web server. Connection to multiple databases in different models Connections are usually created through ActiveRecord::Base. All classes inheriting from ActiveRecord::Base will use this connection. How automatic connection switching works. After reading this guide you will know: How to set up your application for multiple databases. Sep 11, 2024 · Role of ActiveRecord::Base. This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. Returns the connection currently associated with the class. How to use horizontal sharding for multiple databases. connections # => (an array with all active connections) Multiple Databases with Active RecordThis guide covers using multiple databases with your Rails application. ConnectionPool is completely Mar 2, 2022 · For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course. establish_connection and Course and all of its subclasses will use this connection instead. What features are supported and what's still a work in progress. ActiveRecord::Base. AssociationTypeMismatch - The object assigned to the association wasn’t of the type specified in the association definition. When a shard and role is passed, Active Record will first lookup the role, and then look up the connection by shard key. establish_connection specified a non-existent adapter (or a bad spelling of an existing one). establish_connection and retrieved by ActiveRecord::Base. first # finds first Dog record stored on the shard one replica end For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course. Apr 10, 2020 · ActiveRecord::Base. Jul 1, 2024 · Unlike ActiveRecord::Base. Rails automatically establishes a connection to the database defined in the configuration file, and ActiveRecord::Base. . connection_handler). The basic idea is that each thread checks out a database connection from the pool, uses that connection, and checks the connection back in. Active Record Connection Pool ¶ ↑ Connection pool base class for managing Active Record database connections. connected_to(role: :reading, shard: :shard_one_replica) do Dog. connection, which holds connections until the end of the request cycle, with_connection obtain a database connection from the connection pool, yields it to a block of code, and then returns it to the pool after execution for immediate reuse. connection provides access to this connection. w6co7q5 q0lwy1d7 nu6 bxe lv ifkapgn yn7o uncl 58 obm57n