Mincer

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Mincer is an ActiveRecord::Relation wrapper that applies usefull features to your queries. It can:

Paginate Sort Search Dump to Json(Using postgres >= 9.2) Generate digest(useful for caching)

Installation

Add this line to your application’s Gemfile:

gem 'mincer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mincer

Usage

Lets assume we have 2 models

class Employee < ActiveRecord::Base
    belongs_to :company
end

class Company < ActiveRecord::Base
    has_many :employees
end

Generating custom query

rails generate mincer:query EmployeesList

Will generate employees_list_query.rb file in /app/queries/ directory

class EmployeesListQuery < Mincer::Base
  def build_query(relation, args)
    # Apply your conditions, custom selects, etc. to relation
    relation
  end        
end

It inherits from Mincer::Base. Lets instantiate it

class EmployeesListQuery < Mincer::Base
    # method should always return relation
    def build_query(relation, args)
        custom_select = <<-SQL
            employees.id,
            employees.full_name as employee_name,
            companies.name as company_name
        SQL
        relation.joins(:company).select(custom_select)
    end
end

employees = EmployeesListQuery.new(Employee)

employees will delegate all methods, that it can’t find on itself, to relation objects. This means you can use employees as you would use any ActiveRecord::Relation object:

<% employees.each do |employee| %>
    <%= employee.employee_name %>
    <%= employee.company_name %>
<% end %>

Now lets look what more can we do with this object

### Pagination Mincer supports kaminari and will_paginate. In order to use pagination you need to include one of them in your Gemfile. Example of using pagination

employees = EmployeesListQuery.new(Employee, {'page' => 2, 'per_page' => 10})

By default all Mincer objects will use pagination, even if no arguments are passed. To set default values for pagination please refer to kaminari or will_paginate documentation.

To disable pagination you can use class method skip_pagination!:

class EmployeesListQuery < Mincer::Base
    skip_pagination!

    # method should always return relation
    def build_query(relation, args)
        custom_select = <<-SQL
            employees.id,
            employees.full_name as employee_name,
            companies.name as company_name
        SQL
        relation.joins(:company).select(custom_select)
    end
end

### Sorting

Example of using sorting:

employees = EmployeesListQuery.new(Employee, {'sort' => 'employee_name', 'order' => 'DESC'})

By default all Mincer objects will sort by attribute id in ASC order. To change defaults you can override them like this

class EmployeesListQuery < Mincer::Base
    # method should always return relation
    def build_query(relation, args)
        custom_select = <<-SQL
            employees.id,
            employees.full_name as employee_name,
            companies.name as company_name
        SQL
        relation.joins(:company).select(custom_select)
    end

  def default_sort_attribute
    'employee_name'
  end

  def default_sort_order
    'DESC'
  end
end

To disable sorting use class method skip_sorting! like this:

class EmployeesListQuery < Mincer::Base
    skip_sorting!

    # method should always return relation
    def build_query(relation, args)
        custom_select = <<-SQL
            employees.id,
            employees.full_name as employee_name,
            companies.name as company_name
        SQL
        relation.joins(:company).select(custom_select)
    end
end

Mincer will validate sort and order params and will not allow to sort by attributes that do not exist. Default white list consists of all attributes from original scope, in our example Employee.attribute_name. You can expand the list by overriding allowed_sort_attributes list like this:

def allowed_sort_attributes
    super + %w{employee_name company_name}
end This will allow to sort by all Employee attributes + `employee_name` and `company_name`

Or restrict it like this:

def allowed_sort_attributes
    %w{employee_name}
end in this example sorting allowed only by `employee_name`.

ActionView

If you are using Rails or bare ActionView there are few helper methods at your disposal to help generating links for sorting. Currently there are 2 methods available: sort_url_for and sort_class_for.

Example of usage in HAML:

%ul
    %li{ :class => (sort_class_for employees, 'id') }
        = link_to 'ID', sort_url_for(employees, 'id')
    %li{ :class => (sort_class_for employees, 'employee_name') }
        = link_to 'Employee', sort_url_for(employees, 'employee_name')
    %li{ :class => (sort_class_for employees, 'company_name') }
        = link_to 'Company', sort_url_for(employees, 'company_name')

In this example li will receive class="sorted order_down" or class="sorted order_up" if this attribute was used for search. Generated url will be enhanced with sort and order attributes.

### Search

Mincer borrowed allot of search logic from PgSearch. Currently search only works with postgres.

Example of usage:

employees = EmployeesListQuery.new(Employee, {'pattern' => 'whatever'})

By default search will be performed on all text/string columns of current model. If you want to explicitly set searchable columns or you can do so using pg_search method:

pg_search [{ :columns => %w{employees.full_name companies.name} } ]

By default search will use [unaccent] to ignore accent marks. You can read more about unaccent here You need to enable unaccent extension. If you use Rails, please use migration for that:

enable_extension 'unaccent'

or run CREATE EXTENSION IF NOT EXISTS unaccent;

If by any chance you need to disable unaccent:

pg_search [{ :columns => %w{employees.full_name companies.name} }, :ignore_accent => false ]

If you set any_word attribute to true - search will return all items containing any word in the search terms.

pg_search [{ :columns => %w{employees.full_name companies.name} }, :any_word => true ]

If you set ignore_case attribute to true - search will ignore case.

pg_search [{ :columns => %w{employees.full_name companies.name} }, :ignore_case => true ]

Options like unaccent, any_word, ignore_case can be set to be used only on query or document. In Example if you use specific column that already has unaccented and lowercased text with GIN/GIST index and do not want to additionally use unaccent or ignore_case functions on that column(because this will cause index not to work) -you can disable those options. Ex.

pg_search [{ :columns => %w{employees.full_name} }, :ignore_case => {query: true} ]

This way ignore_case function will be used only on pattern that you are searching for and not on columns.

If you set param_name attribute to any other string - this string will be used to extract search term from params(Default param_name = ‘patern’).

pg_search [{ :columns => %w{employees.full_name companies.name} }, :param_name => 's']
employees = EmployeesListQuery.new(Employee, {'s' => 'whatever'})

There are 3 search engines you can use: trigram, fulltext and array. You can specify which one to use, along with other options like this:

pg_search [{ :columns => %w{employees.full_name companies.name}, :engines => [:fulltext, :trigram] ,:ignore_case => true, :threshold => 0.5, :dictionary => :english }] You can also add several search statements:

pg_search [
    { :columns => %w{employees.full_name}, :engines => [:fulltext, :trigram] ,:ignore_case => true},
    { :columns => %w{employees.tags}, :engines => [:array] ,:ignore_case => true, :any_word => true, param_name: 'tag'}
]

employees = EmployeesListQuery.new(Employee, {'patern' => 'whatever', 'tag' => 'fired'}) In this Mincer will search for all employees that are fired OR patern matches full_name. You can use additional option `join_with: :and`. To specify that you need only employees whith matching full name and tag

pg_search [
    { :columns => %w{employees.full_name}, :engines => [:fulltext, :trigram] ,:ignore_case => true},
    { :columns => %w{employees.tags}, :engines => [:array] ,:ignore_case => true, :any_word => true, param_name: 'tag'}
], join_with: :and

You can read details on search engines here: Trigram, Fulltext

### JSON generation

Mincer allows you to dump query result to JSON using Postgres JSON Functions Didn’t had time to do benchmarking, but it’s extremely fast.

Pros:

  1. Speed
  2. No extra dependencies(you don’t need any other JSON generators)

Cons:

  1. Works only with postgres version >= 9.2
  2. If you are using ruby methods to generate some fields - you won’t be able to use them in Mincer objects(Carrierwave image_urls, resource urls). You will have to duplicate logic inside postgres select query.

To dump query result to json string you have to call to_json on Mincer object:

EmployeesListQuery.new(Employee).to_json

In our example it will return something like this

"[{\"id\":1,\"employee_name\":\"John Smith\",\"company_name\":\"Microsoft\"},{\"id\":2,\"employee_name\":\"Jane Smith\",\"company_name\":\"37 Signals\"}]"

In addition you can pass option root to to_json method if you need to include root to json string:

EmployeesListQuery.new(Employee).to_json(root: 'employees')
# returns
"{\"employees\":[{\"id\":1,\"employee_name\":\"John Smith\",\"company_name\":\"Microsoft\"},{\"id\":2,\"employee_name\":\"Jane Smith\",\"company_name\":\"37 Signals\"}]}"

### Digest

Digest is very useful for cache invalidation on your views when you are using custom queries. We will modify a bit example:

class EmployeesListQuery < Mincer::Base
    digest! %w{employee_updated_at company_updated_at}

    def build_query(relation, args)
        custom_select = <<-SQL
            employees.id,
            employees.full_name as employee_name,
            companies.name as company_name,
            employees.updated_at as employee_updated_at,
            companies.updated_at as company_updated_at
        SQL
        relation.joins(:company).select(custom_select)
    end
end

In this example we will use 2 updated_at timestamps to generate digest. Whenever one of them will change - digest will change also. To get digest you should use method digest on Mincer model

EmployeesListQuery.new(Employee).digest # "\\x20e93b4dc5e029130f3d60d697137934"

To generate digest you need to install extension ‘pgcrypto’. If you use Rails, please use migration for that

enable_extension 'pgcrypto'

or run CREATE EXTENSION IF NOT EXISTS pgcrypto;

TODO

  1. Create general configuration for Mincer that would allow to:
    1. Change sort html classes
    2. Change default arguments(sort, order, pattern, page, per_page..)
    3. Disable some processors for all Mincer objects
  2. Create rails generators.
  3. Add coalescing as option for document

Contributing

  1. Fork it
  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 new Pull Request

License

Copyright (c) 2013-2014 Alex Krasynskyi

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.