SchemaPlus is a gem that simply pulls in a collection of other gems from the SchemaPlus family of ActiveRecord extensions

SchemaValidations extends ActiveRecord to automatically create validations by inspecting the database schema. This makes your models more DRY as you no longer need to duplicate NOT NULL, unique, numeric and varchar constraints on the model level.

Provides an internal extension API to ActiveRecord, in the form of middleware-style callback stacks

Adds shorthands and conveniences to ActiveRecord's handling of indexes

Provides a module insertion protocol to facilitate adding features to ActiveRecord

Adds useful accessors to ActiveRecord's Column object.

Adds support in ActiveRecord for PostgreSQL index expressions and operator classes, as well as a shorthand for case-insensitive indexes

Adds support for views to ActiveRecord

In an ActiveRecord migration, set the default to create a foreign key and index for all columns that define relatoins.

Adds support for enum data types in ActiveRecord

Extended support for foreign key constraints in ActiveRecord, including: definition as column attribute; deferrable; and SQLite3 support; cleaner dumps; and more!

SchemaAssociations extends ActiveRecord to automatically create associations by inspecting the database schema. This is more more DRY than the standard behavior, for which in addition to specifying the foreign key in the migration, you must also specify complementary associations in two model files (e.g. a :belongs_to and a :has_many).

Compatibility helpers for the SchemaPlus family of gems

Defines constant ActiveRecord::DB_DEFAULT which, when saved as an attribute's value, causes the db to set the column to its default value.

Extends ActiveRecord migrations to allow an SQL expression for the default value of a column

Adds support for multiple schemas in activerecord when using Postgres

Extends ActiveRecord's handling of tables

If you do not want to setup foreign keys with cascade and ActiveRecord's dependent is too slow for your big database, this is what you are looking for.

Adds useful accessors to ActiveRecord's Column object.

Inserts SchemaMonkey into a rails app.