Clearly Query

A library for constructing an sql query from a hash.

From a hash, validate, construct, and execute a query or create Arel conditions. There are no assumptions or opinions on what is done with the results from the query.

Uses Arel and ActiveRecord.

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Compatible with ActiveRecord 4.2 and 5, and Arel 6 & 7.


Add this line to your application's Gemfile:

gem 'clearly-query'

And then execute:

$ bundle

Or install it yourself as:

$ gem install clearly-query


There are two main public classes in this gem. The Definition class makes use of settings declared in a model. The Composer converts a hash of options into an Arel query.


Contains the query specification for ActiveRecord models.

For example:, Customer.clearly_query_def)


# model/customer.rb
    def self.clearly_query_def
        fields: {
            valid: [:name, :last_contact_at],
            text: [:name],
            mappings: [ # these mappings are built in the database, and are only used for comparison, not projection
                    name: :title,
                    value: Clearly::Query::Helper.string_concat(
                        Clearly::Query::Helper.sql_quoted(' title'))
        associations: [
                join: Order,
                on: Order.arel_table[:customer_id].eq(Customer.arel_table[:id]),
                available: true,
                associations: []

The available specification keys are detailed below.

All field names that are available to include in a query hash:

{fields: { valid: [<Symbols>, ...] } }

All fields that contain text (e.g. varchar, text) that are available to include in a query hash. This must be a subset (or equal) to the valid field array:

{fields: { text:  [<Symbols>, ...] } }

Field mappings that specify a calculated value:

{fields: { mappings: [{ name: <Symbol>, value: <Arel::Nodes::Node, String, Arel::Attribute, others...> }, ... ]  } }

Associations between tables, and whether the association is available in queries or not:

    associations: [
            join: <Model or Arel Table>,
            on: <Arel fragment>,
            available: <true or false>, # is this association available to be used in queries?
            associations: [ <further associations for this table>,  ... ]


Use the Composer to Construct an Arel query from a hash of options. See the query hash specification for a comprehensive overview.

There are two ways to do this. Either compose an ActiveRecord query or compose the Arel conditions.

composer = Clearly::Query::Composer.from_active_record
query_hash = {and: {name: {contains: 'test'}}} # from e.g. HTTP request
model = Customer
arel_conditions = composer.conditions(model, query_hash)
# or
query = composer.query(model, query_hash)

Building custom Arel queries

There is also a class to aid in building Arel queries yourself.

Have a look at the Clearly::Query::Compose::Custom class and the tests for more details.

Helper methods and classes

There are a number of helper methods and classes available to make working with Arel, hashes, and ActiveRecord easier.

Clearly::Query::Cleaner validates a hash to make sure all hash keys are symbols (even in nested hashes and arrays):

cleaned_query_hash =

This library uses the custom error Clearly::Query::QueryArgumentError (it inherits from ArgumentError).

There are a bunch of validation methods in the Clearly::Query::Validate module. Sometimes duck typing is not that great :/

There is also the Clearly::Query::Graph class, currently used only for constructing root to leaf routes for building joins.

Class methods in the Clearly::Query::Helper class provide abstractions over differences in database string concatenation, help construct Arel infix operators, EXISTS clauses, literals, and SQL fragments. These helper methods are mostly a result of obscure or odd functionality. It's a collection of Arel experience that will probably be helpful.

More Information about Arel


  1. Fork this repo
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new pull request