diff options
Diffstat (limited to 'activerecord/lib/active_record/relation')
3 files changed, 46 insertions, 25 deletions
diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb index 15f838a5ab..fb4388d4b2 100644 --- a/activerecord/lib/active_record/relation/batches.rb +++ b/activerecord/lib/active_record/relation/batches.rb @@ -2,20 +2,26 @@ require 'active_support/core_ext/object/blank' module ActiveRecord module Batches - # Yields each record that was found by the find +options+. The find is - # performed by find_in_batches with a batch size of 1000 (or as + # Looping through a collection of records from the database + # (using the +all+ method, for example) is very inefficient + # since it will try to instantiate all the objects at once. + # + # In that case, batch processing methods allow you to work + # with the records in batches, thereby greatly reducing memory consumption. + # + # The <tt>find_each</tt> method uses <tt>find_in_batches</tt> with a batch size of 1000 (or as # specified by the <tt>:batch_size</tt> option). # - # Example: + # Person.all.find_each do |person| + # person.do_awesome_stuff + # end # # Person.where("age > 21").find_each do |person| # person.party_all_night! # end # - # Note: This method is only intended to use for batch processing of - # large amounts of records that wouldn't fit in memory all at once. If - # you just need to loop over less than 1000 records, it's probably - # better just to use the regular find methods. + # You can also pass the <tt>:start</tt> option to specify + # an offset to control the starting point. def find_each(options = {}) find_in_batches(options) do |records| records.each { |record| yield record } @@ -39,12 +45,15 @@ module ActiveRecord # primary keys. You can't set the limit either, that's used to control # the batch sizes. # - # Example: - # # Person.where("age > 21").find_in_batches do |group| # sleep(50) # Make sure it doesn't get too crowded in there! # group.each { |person| person.party_all_night! } # end + # + # # Let's process the next 2000 records + # Person.all.find_in_batches(start: 2000, batch_size: 2000) do |group| + # group.each { |person| person.party_all_night! } + # end def find_in_batches(options = {}) options.assert_valid_keys(:start, :batch_size) diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb index 31d99f0192..ad49c80e4f 100644 --- a/activerecord/lib/active_record/relation/calculations.rb +++ b/activerecord/lib/active_record/relation/calculations.rb @@ -16,9 +16,16 @@ module ActiveRecord # # Person.count(:age, distinct: true) # # => counts the number of different age values + # + # Person.where("age > 26").count { |person| gender == 'female' } + # # => queries people where "age > 26" then count the loaded results filtering by gender def count(column_name = nil, options = {}) - column_name, options = nil, column_name if column_name.is_a?(Hash) - calculate(:count, column_name, options) + if block_given? + self.to_a.count { |item| yield item } + else + column_name, options = nil, column_name if column_name.is_a?(Hash) + calculate(:count, column_name, options) + end end # Calculates the average value on a given column. Returns +nil+ if there's @@ -52,9 +59,13 @@ module ActiveRecord # +calculate+ for examples with options. # # Person.sum('age') # => 4562 + # # => returns the total sum of all people's age + # + # Person.where('age > 100').sum { |person| person.age - 100 } + # # queries people where "age > 100" then perform a sum calculation with the block returns def sum(*args) if block_given? - self.to_a.sum(*args) {|*block_args| yield(*block_args)} + self.to_a.sum(*args) { |item| yield item } else calculate(:sum, *args) end @@ -118,7 +129,7 @@ module ActiveRecord # Person.all.map(&:name) # # Pluck returns an <tt>Array</tt> of attribute values type-casted to match - # the plucked column name, if it can be deduced. Plucking a SQL fragment + # the plucked column name, if it can be deduced. Plucking an SQL fragment # returns String values by default. # # Examples: diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb index 4fedd33d64..5f6898b45a 100644 --- a/activerecord/lib/active_record/relation/finder_methods.rb +++ b/activerecord/lib/active_record/relation/finder_methods.rb @@ -7,8 +7,6 @@ module ActiveRecord # If no record can be found for all of the listed ids, then RecordNotFound will be raised. If the primary key # is an integer, find by id coerces its arguments using +to_i+. # - # ==== Examples - # # Person.find(1) # returns the object for ID = 1 # Person.find("1") # returns the object for ID = 1 # Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6) @@ -49,7 +47,6 @@ module ActiveRecord # # Post.find_by name: 'Spartacus', rating: 4 # Post.find_by "published_at < ?", 2.weeks.ago - # def find_by(*args) where(*args).take end @@ -64,8 +61,6 @@ module ActiveRecord # order. The order will depend on the database implementation. # If an order is supplied it will be respected. # - # Examples: - # # Person.take # returns an object fetched by SELECT * FROM people # Person.take(5) # returns 5 objects fetched by SELECT * FROM people LIMIT 5 # Person.where(["name LIKE '%?'", name]).take @@ -82,12 +77,11 @@ module ActiveRecord # Find the first record (or first N records if a parameter is supplied). # If no order is defined it will order by primary key. # - # Examples: - # # Person.first # returns the first object fetched by SELECT * FROM people # Person.where(["user_name = ?", user_name]).first # Person.where(["user_name = :u", { :u => user_name }]).first # Person.order("created_on DESC").offset(5).first + # Person.first(3) # returns the first three objects fetched by SELECT * FROM people LIMIT 3 def first(limit = nil) if limit if order_values.empty? && primary_key @@ -109,11 +103,18 @@ module ActiveRecord # Find the last record (or last N records if a parameter is supplied). # If no order is defined it will order by primary key. # - # Examples: - # # Person.last # returns the last object fetched by SELECT * FROM people # Person.where(["user_name = ?", user_name]).last # Person.order("created_on DESC").offset(5).last + # Person.last(3) # returns the last three objects fetched by SELECT * FROM people. + # + # Take note that in that last case, the results are sorted in ascending order: + # + # [#<Person id:2>, #<Person id:3>, #<Person id:4>] + # + # and not: + # + # [#<Person id:4>, #<Person id:3>, #<Person id:2>] def last(limit = nil) if limit if order_values.empty? && primary_key @@ -132,7 +133,8 @@ module ActiveRecord last or raise RecordNotFound end - # Examples: + # Runs the query on the database and returns records with the used query + # methods. # # Person.all # returns an array of objects for all the rows fetched by SELECT * FROM people # Person.where(["category IN (?)", categories]).limit(50).all @@ -163,11 +165,10 @@ module ActiveRecord # 'Jamie'</tt>), since it would be sanitized and then queried against # the primary key column, like <tt>id = 'name = \'Jamie\''</tt>. # - # ==== Examples # Person.exists?(5) # Person.exists?('5') - # Person.exists?(:name => "David") # Person.exists?(['name LIKE ?', "%#{query}%"]) + # Person.exists?(:name => "David") # Person.exists? def exists?(id = false) id = id.id if ActiveRecord::Model === id |