ActiveRecord Enhanced SQLite3 Adapter

Enhance ActiveRecord's 7.1 SQLite3 adapter. Adds support for:

• generated columns,
• deferred foreign keys,
• PRAGMA tuning,
• and extension loading

Install the gem and add to the application's Gemfile by executing:

$ bundle add activerecord-enhancedsqlite3-adapter

This gem hooks into your Rails application to enhance the SQLite3Adapter automatically. No setup required!

Once installed, you can take advantage of the added features.

One optional advanced feature is to have this gem isolate reading and writing connection pools. This is useful if you have a large amount of write operations and want to avoid blocking reads.

You can configure this gem via the Rails configuration object, under the enhanced_sqlite3 key. Currently, only 1 configuration option is available:

• isolate_connection_pools - Whether or not to isolate reading from writing connection pools. See below for more information.

You can now create virtual columns, both stored and dynamic. The SQLite docs explain the difference:

Generated columns can be either VIRTUAL or STORED. The value of a VIRTUAL column is computed when read, whereas the value of a STORED column is computed when the row is written. STORED columns take up space in the database file, whereas VIRTUAL columns use more CPU cycles when being read.

The default is to create dynamic/virtual columns.

create_table :virtual_columns, force: true do |t|
  t.string :name
  t.virtual :upper_name, type: :string, as: "UPPER(name)", stored: true
  t.virtual :lower_name, type: :string, as: "LOWER(name)", stored: false
  t.virtual :octet_name, type: :integer, as: "LENGTH(name)"
end

You can now specify whether or not a foreign key should be deferrable, whether :deferred or :immediate.

:deferred foreign keys mean that the constraint check will be done once the transaction is committed and allows the constraint behavior to change within transaction. :immediate means that constraint check is immediate and allows the constraint behavior to change within transaction. The default is :immediate.

add_reference :person, :alias, foreign_key: { deferrable: :deferred }
add_reference :alias, :person, foreign_key: { deferrable: :deferred }

Pass any PRAGMA key-value pair under a pragmas list in your config/database.yml file to ensure that these configuration settings are applied to all database connections.

default: &default
  adapter: sqlite3
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  pragmas:
    # level of database durability, 2 = "FULL" (sync on every write), other values include 1 = "NORMAL" (sync every 1000 written pages) and 0 = "NONE"
    # https://www.sqlite.org/pragma.html#pragma_synchronous
    synchronous: "FULL"

There are a number of SQLite extensions available as Ruby gems. In order to load the extensions, you need to install the gem (bundle add {extension-name}) and then load it into the database connections. In order to support the latter, this gem enhances the config/database.yml file to support an extensions array. For example, to install and load an extension for supporting ULIDs, we would do:

$ bundle add sqlite_ulid

then

default: &default
  adapter: sqlite3
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  extensions:
    - sqlite_ulid

By default, Rails uses a single connection pool for both reading and writing. This can lead to contention if you have a large number of write operations. This gem allows you to isolate the connection pools for reading and writing.

To enable this feature, set the isolate_connection_pools configuration option to true in your config/environments/*.rb file or config/application.rb file:

config.enhanced_sqlite3.isolate_connection_pools = true

If enabled, the gem will patch your application in 3 ways:

1. define separate reader and writer database configurations
2. activate Rails' automatic role database switching middleware, defaulting all requests to the reader connection pool
3. patch the ActiveRecord #transaction method to switch to the writer connection pool for write operations
4. patch the ActiveRecord #log method to log the database name for each database operation

This feature is experimental and may not work with all Rails configurations. Please report any issues you encounter.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/fractaledmind/activerecord-enhancedsqlite3-adapter.

The gem is available as open source under the terms of the MIT License.