Arel Extensions

Adds support for missing SQL operators and functions to Arel for ActiveRecord.

Installation

Add this line to your application's Gemfile:

gem 'arel-extensions', require: 'arel/extensions'

And then execute:

$ bundle

Or install it yourself as:

$ gem install arel-extensions

Usage

Just require 'arel-extensions' and use Arel / ActiveRecord as you normally would.

It adds the methods and nodes below to Arel::Attributes::Attribute and to ActiveRecord relations. Most operators generate PostgreSQL-specific SQL.

Attribute-level helpers are used through an Arel attribute, e.g. Model.arel_table[:column], typically inside where or order.

What it adds

DISTINCT ON (ActiveRecord)

Added to relations (and as a class method via Model.distinct_on):

User.distinct_on(:email)          # SELECT DISTINCT ON (users.email) ...
User.distinct_on(:a, :b)          # DISTINCT ON (users.a, users.b)

uniq_on is an alias of distinct_on.

Ordering with NULLS FIRST / LAST

col = User.arel_table[:name]
User.order(col.asc(:nulls_last))    # ... ORDER BY users.name ASC NULLS LAST
User.order(col.desc(:nulls_first))  # ... ORDER BY users.name DESC NULLS FIRST

A RANDOM() ordering node is also provided.

Array predicates

tags = Post.arel_table[:tags]
tags.contained_by(other)   # tags <@ other
tags.excludes(other)       # NOT (tags @> other)

JSON / JSONB predicates

data = User.arel_table[:data]

data.key('name')            # data #>'{name}'   (aliases: data['name'], data.index('name'))
data.dig('address', 'zip')  # data #>'{address,zip}'
data.has_key('name')        # data ? 'name'
data.has_keys('a', 'b')     # data ?& array['a','b']
data.has_any_key('a', 'b')  # data ?| array['a','b']
data.cast_as('int')         # (data)::int

Full-text search

body = Article.arel_table[:body]
body.ts_query('quick & fox')          # to_tsvector(body) @@ to_tsquery('quick & fox')
body.ts_query('quick & fox', 'english')

Nodes for to_tsvector, to_tsquery, @@ (TSMatch), ts_rank, and ts_rank_cd are available for building ranking expressions.

GIS predicates (optional)

area = Place.arel_table[:area]
area.intersects(value)   # ST_Intersects(area, value)
area.within(value)       # ST_Within(area, value)

value may be an Arel node, an RGeo geometry, a WKT/WKB string, or a GeoJSON hash. Anything other than an Arel node requires the rgeo gem, so add it to your Gemfile if you use these:

gem 'rgeo'

Binary values

BinaryValue and HexEncodedBinaryValue nodes for embedding binary data (escaped bytea and \x-encoded hex, respectively).