# This awesomeness is taken from Mongoid, Thanks Durran!
module MongoDoc #:nodoc:
# The +Criteria+ class is the core object needed in Mongoid to retrieve
# objects from the database. It is a DSL that essentially sets up the
# selector and options arguments that get passed on to a Mongo::Collection
# in the Ruby driver. Each method on the +Criteria+ returns self to they
# can be chained in order to create a readable criterion to be executed
# against the database.
#
# Example setup:
#
# criteria = Criteria.new
#
# criteria.select(:field => "value").only(:field).skip(20).limit(20)
#
# criteria.execute
class Criteria
SORT_REVERSALS = {
:asc => :desc,
:ascending => :descending,
:desc => :asc,
:descending => :ascending
}
include Enumerable
attr_reader :klass, :options, :selector
# Returns true if the supplied +Enumerable+ or +Criteria+ is equal to the results
# of this +Criteria+ or the criteria itself.
#
# This will force a database load when called if an enumerable is passed.
#
# Options:
#
# other: The other +Enumerable+ or +Criteria+ to compare to.
def ==(other)
case other
when Criteria
self.selector == other.selector && self.options == other.options
when Enumerable
@collection ||= execute
return (@collection == other)
else
return false
end
end
AGGREGATE_REDUCE = "function(obj, prev) { prev.count++; }"
# Aggregate the criteria. This will take the internally built selector and options
# and pass them on to the Ruby driver's +group()+ method on the collection. The
# collection itself will be retrieved from the class provided, and once the
# query has returned it will provided a grouping of keys with counts.
#
# Example:
#
# criteria.select(:field1).where(:field1 => "Title").aggregate(Person)
def aggregate(use_klass = nil)
aggregating_klass = use_klass ? use_klass : klass
aggregating_klass.collection.group(options[:fields], selector, { :count => 0 }, AGGREGATE_REDUCE)
end
# Adds a criterion to the +Criteria+ that specifies values that must all
# be matched in order to return results. Similar to an "in" clause but the
# underlying conditional logic is an "AND" and not an "OR". The MongoDB
# conditional operator that will be used is "$all".
#
# Options:
#
# selections: A +Hash+ where the key is the field name and the value is an
# +Array+ of values that must all match.
#
# Example:
#
# criteria.every(:field => ["value1", "value2"])
#
# criteria.every(:field1 => ["value1", "value2"], :field2 => ["value1"])
#
# Returns: self
def every(selections = {})
selections.each { |key, value| selector[key] = { "$all" => value } }; self
end
# Get the count of matching documents in the database for the +Criteria+.
#
# Example:
#
# criteria.count
#
# Returns: Integer
def count
@count ||= klass.collection.find(selector, options.dup).count
end
# Iterate over each +Document+ in the results and pass each document to the
# block.
#
# Example:
#
# criteria.each { |doc| p doc }
def each(&block)
@collection ||= execute
if block_given?
@collection.each(&block)
else
self
end
end
# Adds a criterion to the +Criteria+ that specifies values that are not allowed
# to match any document in the database. The MongoDB conditional operator that
# will be used is "$ne".
#
# Options:
#
# excludes: A +Hash+ where the key is the field name and the value is a
# value that must not be equal to the corresponding field value in the database.
#
# Example:
#
# criteria.excludes(:field => "value1")
#
# criteria.excludes(:field1 => "value1", :field2 => "value1")
#
# Returns: self
def excludes(exclusions = {})
exclusions.each { |key, value| selector[key] = { "$ne" => value } }; self
end
# Adds a criterion to the +Criteria+ that specifies additional options
# to be passed to the Ruby driver, in the exact format for the driver.
#
# Options:
#
# extras: A +Hash+ that gets set to the driver options.
#
# Example:
#
# criteria.extras(:limit => 20, :skip => 40)
#
# Returns: self
def extras(extras)
options.merge!(extras)
filter_options
self
end
# Return the first result for the +Criteria+.
#
# Example:
#
# Criteria.select(:name).where(:name = "Chrissy").one
def one
klass.collection.find_one(selector, options.dup)
end
alias :first :one
GROUP_REDUCE = "function(obj, prev) { prev.group.push(obj); }"
# Groups the criteria. This will take the internally built selector and options
# and pass them on to the Ruby driver's +group()+ method on the collection. The
# collection itself will be retrieved from the class provided, and once the
# query has returned it will provided a grouping of keys with objects.
#
# Example:
#
# criteria.select(:field1).where(:field1 => "Title").group(Person)
def group(use_klass = nil)
(use_klass || klass).collection.group(
options[:fields],
selector,
{ :group => [] },
GROUP_REDUCE
).collect {|docs| docs["group"] = MongoDoc::BSON.decode(docs["group"]); docs }
end
# Adds a criterion to the +Criteria+ that specifies values where any can
# be matched in order to return results. This is similar to an SQL "IN"
# clause. The MongoDB conditional operator that will be used is "$in".
#
# Options:
#
# inclusions: A +Hash+ where the key is the field name and the value is an
# +Array+ of values that any can match.
#
# Example:
#
# criteria.in(:field => ["value1", "value2"])
#
# criteria.in(:field1 => ["value1", "value2"], :field2 => ["value1"])
#
# Returns: self
def in(inclusions = {})
inclusions.each { |key, value| selector[key] = { "$in" => value } }; self
end
# Adds a criterion to the +Criteria+ that specifies an id that must be matched.
#
# Options:
#
# object_id: A +String+ representation of a Mongo::ObjectID
#
# Example:
#
# criteria.id("4ab2bc4b8ad548971900005c")
#
# Returns: self
def id(object_id)
selector[:_id] = object_id; self
end
# Create the new +Criteria+ object. This will initialize the selector
# and options hashes, as well as the type of criteria.
#
# Options:
#
# type: One of :all, :first:, or :last
# klass: The class to execute on.
def initialize(klass)
@selector, @options, @klass = {}, {}, klass
end
# Return the last result for the +Criteria+. Essentially does a find_one on
# the collection with the sorting reversed. If no sorting parameters have
# been provided it will default to ids.
#
# Example:
#
# Criteria.select(:name).where(:name = "Chrissy").last
def last
opts = options.dup
sorting = opts[:sort]
sorting = [[:_id, :asc]] unless sorting
opts[:sort] = sorting.collect { |option| [ option.first, Criteria.invert(option.last) ] }
klass.collection.find_one(selector, opts)
end
# Adds a criterion to the +Criteria+ that specifies the maximum number of
# results to return. This is mostly used in conjunction with skip()
# to handle paginated results.
#
# Options:
#
# value: An +Integer+ specifying the max number of results. Defaults to 20.
#
# Example:
#
# criteria.limit(100)
#
# Returns: self
def limit(value = 20)
options[:limit] = value; self
end
# Merges another object into this +Criteria+. The other object may be a
# +Criteria+ or a +Hash+. This is used to combine multiple scopes together,
# where a chained scope situation may be desired.
#
# Options:
#
# other: The +Criteria+ or +Hash+ to merge with.
#
# Example:
#
# criteria.merge({ :conditions => { :title => "Sir" } })
def merge(other)
selector.update(other.selector)
options.update(other.options)
end
# Used for chaining +Criteria+ scopes together in the for of class methods
# on the +Document+ the criteria is for.
#
# Options:
#
# name: The name of the class method on the +Document+ to chain.
# args: The arguments passed to the method.
#
# Example:
#
# class Person < Mongoid::Document
# field :title
# field :terms, :type => Boolean, :default => false
#
# class << self
# def knights
# all(:conditions => { :title => "Sir" })
# end
#
# def accepted
# all(:conditions => { :terms => true })
# end
# end
# end
#
# Person.accepted.knights #returns a merged criteria of the 2 scopes.
#
# Returns: Criteria
def method_missing(name, *args)
new_scope = klass.send(name)
new_scope.merge(self)
new_scope
end
# Adds a criterion to the +Criteria+ that specifies values where none
# should match in order to return results. This is similar to an SQL "NOT IN"
# clause. The MongoDB conditional operator that will be used is "$nin".
#
# Options:
#
# exclusions: A +Hash+ where the key is the field name and the value is an
# +Array+ of values that none can match.
#
# Example:
#
# criteria.not_in(:field => ["value1", "value2"])
#
# criteria.not_in(:field1 => ["value1", "value2"], :field2 => ["value1"])
#
# Returns: self
def not_in(exclusions)
exclusions.each { |key, value| selector[key] = { "$nin" => value } }; self
end
# Returns the offset option. If a per_page option is in the list then it
# will replace it with a skip parameter and return the same value. Defaults
# to 20 if nothing was provided.
def offset
options[:skip]
end
# Adds a criterion to the +Criteria+ that specifies the sort order of
# the returned documents in the database. Similar to a SQL "ORDER BY".
#
# Options:
#
# params: An +Array+ of [field, direction] sorting pairs.
#
# Example:
#
# criteria.order_by([[:field1, :asc], [:field2, :desc]])
#
# Returns: self
def order_by(params = [])
options[:sort] = params; self
end
# Either returns the page option and removes it from the options, or
# returns a default value of 1.
def page
if options[:skip] && options[:limit]
(options[:skip].to_i + options[:limit].to_i) / options[:limit].to_i
else
1
end
end
# Executes the +Criteria+ and paginates the results.
#
# Example:
#
# criteria.paginate
def paginate
@collection ||= execute
WillPaginate::Collection.create(page, per_page, count) do |pager|
pager.replace(@collection.to_a)
end
end
# Returns the number of results per page or the default of 20.
def per_page
(options[:limit] || 20).to_i
end
# Adds a criterion to the +Criteria+ that specifies the fields that will
# get returned from the Document. Used mainly for list views that do not
# require all fields to be present. This is similar to SQL "SELECT" values.
#
# Options:
#
# args: A list of field names to retrict the returned fields to.
#
# Example:
#
# criteria.select(:field1, :field2, :field3)
#
# Returns: self
def select(*args)
options[:fields] = args.flatten if args.any?; self
end
# Adds a criterion to the +Criteria+ that specifies how many results to skip
# when returning Documents. This is mostly used in conjunction with
# limit() to handle paginated results, and is similar to the
# traditional "offset" parameter.
#
# Options:
#
# value: An +Integer+ specifying the number of results to skip. Defaults to 0.
#
# Example:
#
# criteria.skip(20)
#
# Returns: self
def skip(value = 0)
options[:skip] = value; self
end
# Translate the supplied arguments into a +Criteria+ object.
#
# If the passed in args is a single +String+, then it will
# construct an id +Criteria+ from it.
#
# If the passed in args are a type and a hash, then it will construct
# the +Criteria+ with the proper selector, options, and type.
#
# Options:
#
# args: either a +String+ or a +Symbol+, +Hash combination.
#
# Example:
#
# Criteria.translate(Person, "4ab2bc4b8ad548971900005c")
#
# Criteria.translate(Person, :conditions => { :field => "value"}, :limit => 20)
#
# Returns a new +Criteria+ object.
def self.translate(klass, params = {})
return new(klass).id(params).one if params.is_a?(String)
return new(klass).where(params.delete(:conditions)).extras(params)
end
# Adds a criterion to the +Criteria+ that specifies values that must
# be matched in order to return results. This is similar to a SQL "WHERE"
# clause. This is the actual selector that will be provided to MongoDB,
# similar to the Javascript object that is used when performing a find()
# in the MongoDB console.
#
# Options:
#
# selectior: A +Hash+ that must match the attributes of the +Document+.
#
# Example:
#
# criteria.where(:field1 => "value1", :field2 => 15)
#
# Returns: self
def where(add_selector = {})
selector.merge!(add_selector); self
end
protected
# Execute the criteria. This will take the internally built selector and options
# and pass them on to the Ruby driver's +find()+ method on the collection. The
# collection itself will be retrieved from the class provided.
#
# Returns either a cursor or an empty array.
def execute
cursor = klass.collection.find(selector, options.dup)
if cursor
@count = cursor.count
cursor
else
[]
end
end
# Filters the unused options out of the options +Hash+. Currently this
# takes into account the "page" and "per_page" options that would be passed
# in if using will_paginate.
def filter_options
page_num = options.delete(:page)
per_page_num = options.delete(:per_page)
if (page_num || per_page_num)
options[:limit] = (per_page_num || 20).to_i
options[:skip] = (page_num || 1).to_i * options[:limit] - options[:limit]
end
end
def self.invert(order)
SORT_REVERSALS[order]
end
end
end