ActiveRecord::HashOptions

This is stalled because it is too hard to implement string comparisions that are the same in the database and in sql. The solution will probably be simple but needs to be done. Definintely need to use the same locale for ruby as we are using in the database.

This enhances active record so that it can be used in more cases than the pure equality case.

Active record hash syntax only support equality. For things like case insensitivity or regular expression matching, arel is needed.

It would be nice to use where(:col => val) syntax for other operators, too.

Active record caches data in an association. When a similar association has a where clause, it also needs to be downloaded since the where() clause is only executable in the database.

has_many :books has_many :overdue_books, -> { where(:overdue => true) }

It would be nice to only have 1 copy of the data locally.

Active record only supports sorting case sensitive.

It would be nice to use standard order()

The user needs to search and provide custom query logic.

Hash Options handles the first use case but has grand aspirations to handle all 4.

Thanks to the example from codesnik

There are a number of ways to use active record hash options, contingent upon how much you want to monkey patch your environment.

require 'active_record/hash_options'

Person.where(:name => ActiveRecord::HashOptions::LIKE('Smith%'))
Person.where(:age => ActiveRecord::HashOptions::GTE(21))

require 'active_record/hash_options'
include ActiveRecord::HashOptions

Person.where(:name => LIKE('Smith%'))
Person.where.not(:age => GTE(21))

ActiveRecord::HashOptions.filter(Person.all, :name => LIKE('Smith%'))
ActiveRecord::HashOptions.filter(Person.all.to_a, :name => LIKE('Smith%'))
ActiveRecord::HashOptions.filter(Person.all.to_a, :age => GTE(21), true)

require 'active_record/hash_options'
include ActiveRecord::HashOptions::Helpers

Person.where(:name => like('Smith%'))
Person.where.not(:age => gte(21))

ActiveRecord::HashOptions.filter(Person.all.to_a, :name => like('Smith%'))

require 'active_record/hash_options'
include ActiveRecord::HashOptions::Helpers
Array.send(:include, ActiveRecord::HashOptions::Enumerable)

Person.all.to_a.where(:name => like('Smith%'))
Person.all.to_a.where.not(:age => gte(21))

Sql uses null to represent unknown, ruby uses nil to represent no value. These are similar. Unfortunatly sql and ruby handle comparisons with these values differently.

In ruby, you can compare a value with nil. x != nil is true and nil == nil is true In sql you can not. x <> null and null = null are both false. Instead, sql has a special operator, IS NULL. x IS NOT NULL and null IS NULL are both true. This causes ruby and sql logic to deviate a little.

ActiveRecord takes the ruby definition of equality and translates where(:x => nil) to be x IS NULL and not literally x == NULL. Please note, this also means a null in a column is handle differently from a null in a literal comparison clause.

The implications can be seen by comparing ruby, sql, and active record of the same logic. The ruby expression is shown, but is easily converted to the other forms:

Arel, Active Record, and Hash Options all follow the same logic

So note, in active record, the following nuances occur for the null edge case, especially around inequality. It stems around a null literal is treated differentaly than a null in a column.

Comunicative property does not work: nil != 'x' has a different value from 'x' != nil. Distributive property does not work: nil != 'x' has a different value from !(x == nil). Also note, the in the column to column case, this is not always what the user intended.

Add this line to your application's Gemfile:

gem 'activerecord-hash_options'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-hash_options

After checking out the repo, run bin/setup to install dependencies. Then, run rake to run the tests.

You can also run bin/console for an interactive prompt that will allow you to experiment. This runs against sqlite and has the Author, Book, Bookmark, and Photo models avaiable for your convenience.

Bug reports and pull requests are welcome on GitHub at https://github.com/kbrock/activerecord-hash_options.

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