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# SchemaAutoForeignKeys


SchemaAutoForeignKeys is part of the [SchemaPlus](https://github.com/SchemaPlus/) family of Ruby on Rails ActiveRecord extension gems.

## Usage

Many of us think that it should goes without saying that if you define a foreign key *relation* in your database you should also define a foreign key *constraint*.

Similarly, it should go without saying that if you have a foreign key *constraint* on a column, you should also have an *index* on that column.

And if you include the `schema_auto_foreign_keys` gem, these will also go without typing!  schema_auto_foreign_keys simply turns on some default behavior in your migrations:

```ruby
t.integer :user_id  # any column named xxxx_id defaults to...
t.integer :user_id, foreign_key: true, index: true

t.references :user # references defaults to...
t.references :user, foreign_key: true, index: true

t.belongs_to :user # belongs_to default to...
t.belongs_to :user, foreign_key: true, index: true
```

Note that schema_auto_foreign_keys depends on the [schema_plus_foreign_keys](https://github.com/SchemaPlus/schema_plus_foreign_keys) and [schema_plus_indexes](https://github.com/SchemaPlus/schema_plus_indexes) gems, and so makes available their migration shortcuts.

There is actually one difference between an auto-created index and specifying `index: true`: if you don't specify anything, schema_auto_foreign_keys will maintain "ownership" of the auto-created index:  It will remove the index if the foreign key gets removed; and it will rename the index if the table gets renamed.

### Overriding

If you need specific paramaters other than the default, you can of course specify them:

```ruby
t.integer :user_id, index: :unique  # "has one" relationship between users and this 
model
t.integer :user_id, on_delete: :cascade
```

If you don't want a foreign key constraint (e.g. because "product_id" is a domain-level string rather than a foreign key), or an index just specify falsey:

```rugy
t.integer :product_id, foreign_key: false # also implies index: false
t.integer :product_id, references: nil
t.integer :user_id, index: false
```

## Configuration

SchemaAutoForeignKeys adds two new entries to SchemaPlus::ForeignKeys' config:

```ruby
SchemaPlus::ForeignKeys.setup do |config|
   config.auto_create = true # default for schema_auto_foreign_keys
   config.auto_index = true # default for schema_auto_foreign_keys
end
```

You can also configure the behavior per-table in a migration:

```ruby
create_table :posts, foreign_keys: { auto_create: true, auto_index: true } do |t|
   t.integer :author_id
endf
```


## Installation

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As usual:

```ruby
gem "schema_auto_foreign_keys"                # in a Gemfile
gem.add_dependency "schema_auto_foreign_keys" # in a .gemspec
```

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## Compatibility

SchemaAutoForeignKeys is tested on:

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* ruby **2.1.5** with activerecord **4.2.0**, using **mysql2**, **sqlite3** or **postgresql**
* ruby **2.1.5** with activerecord **4.2.1**, using **mysql2**, **sqlite3** or **postgresql**

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### Platform-specific Notes:

MySQL automatically creates indexes for foreign key constraints, so when used with MySQL, schema_auto_foreign_keys doesn't include the auto-index capability.

SQlite3 doesn't support renaming the auto-index whtn the table name changes.



## History

* 0.1.2 - Missing require
* 0.1.1 - Explicit gem dependencies
* 0.1.0 - Initial release, extracted from schema_plus 2.0.0.pre*

## Development & Testing

Are you interested in contributing to SchemaAutoForeignKeys?  Thanks!  Please follow
the standard protocol: fork, feature branch, develop, push, and issue pull
request.

Some things to know about to help you develop and test:

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* **schema_dev**:  SchemaAutoForeignKeys uses [schema_dev](https://github.com/SchemaPlus/schema_dev) to
  facilitate running rspec tests on the matrix of ruby, activerecord, and database
  versions that the gem supports, both locally and on
  [travis-ci](http://travis-ci.org/SchemaPlus/schema_auto_foreign_keys)

  To to run rspec locally on the full matrix, do:

        $ schema_dev bundle install
        $ schema_dev rspec

  You can also run on just one configuration at a time;  For info, see `schema_dev --help` or the [schema_dev](https://github.com/SchemaPlus/schema_dev) README.

  The matrix of configurations is specified in `schema_dev.yml` in
  the project root.


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* **schema_monkey**: SchemaAutoForeignKeys is implemented as a
  [schema_monkey](https://github.com/SchemaPlus/schema_monkey) client,
  using [schema_monkey](https://github.com/SchemaPlus/schema_monkey)'s
  convention-based protocols for extending ActiveRecord and using middleware stacks.

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