module ActiveRecord::FinderMethods
Constants
- ONE_AS_ONE
Public Instance Methods
Source
# File lib/active_record/relation/finder_methods.rb, line 357 def exists?(conditions = :none) return false if @none if Base === conditions raise ArgumentError, <<-MSG.squish You are passing an instance of ActiveRecord::Base to `exists?`. Please pass the id of the object by calling `.id`. MSG end return false if !conditions || limit_value == 0 if eager_loading? relation = apply_join_dependency(eager_loading: false) return relation.exists?(conditions) end relation = construct_relation_for_exists(conditions) return false if relation.where_clause.contradiction? skip_query_cache_if_necessary do with_connection do |c| c.select_rows(relation.arel, "#{model.name} Exists?").size == 1 end end end
Returns true if a record exists in the table that matches the id
or conditions given, or false otherwise. The argument can take six forms:
-
Integer - Finds the record with this primary key.
-
String - Finds the record with a primary key corresponding to this string (such as
'5'
). -
Array - Finds the record that matches these
where
-style conditions (such as['name LIKE ?', "%#{query}%"]
). -
Hash - Finds the record that matches these
where
-style conditions (such as{name: 'David'}
). -
false
- Returns alwaysfalse
. -
No args - Returns
false
if the relation is empty,true
otherwise.
For more information about specifying conditions as a hash or array, see the Conditions section in the introduction to ActiveRecord::Base
.
Note: You can’t pass in a condition as a string (like name = 'Jamie'
), since it would be sanitized and then queried against the primary key column, like id = 'name = \'Jamie\''
.
Person.exists?(5) Person.exists?('5') Person.exists?(['name LIKE ?', "%#{query}%"]) Person.exists?(id: [1, 4, 8]) Person.exists?(name: 'David') Person.exists?(false) Person.exists? Person.where(name: 'Spartacus', rating: 4).exists?
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# File lib/active_record/relation/finder_methods.rb, line 271 def fifth find_nth 4 end
Find the fifth record. If no order is defined it will order by primary key.
Person.fifth # returns the fifth object fetched by SELECT * FROM people Person.offset(3).fifth # returns the fifth object from OFFSET 3 (which is OFFSET 7) Person.where(["user_name = :u", { u: user_name }]).fifth
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# File lib/active_record/relation/finder_methods.rb, line 277 def fifth! fifth || raise_record_not_found_exception! end
Same as fifth
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File lib/active_record/relation/finder_methods.rb, line 98 def find(*args) return super if block_given? find_with_ids(*args) end
Find by id - This can either be a specific id (ID), a list of ids (ID, ID, ID), or an array of ids ([ID, ID, ID]). ‘ID` refers to an “identifier”. For models with a single-column primary key, `ID` will be a single value, and for models with a composite primary key, it will be an array of values. If one or more records cannot be found for the requested ids, then ActiveRecord::RecordNotFound
will be raised. If the primary key is an integer, find by id coerces its arguments by using to_i
.
Person.find(1) # returns the object for ID = 1 Person.find("1") # returns the object for ID = 1 Person.find("31-sarah") # returns the object for ID = 31 Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6) Person.find([7, 17]) # returns an array for objects with IDs in (7, 17), or with composite primary key [7, 17] Person.find([1]) # returns an array for the object with ID = 1 Person.where("administrator = 1").order("created_on DESC").find(1)
Find a record for a composite primary key model¶ ↑
TravelRoute.primary_key = [:origin, :destination] TravelRoute.find(["Ottawa", "London"]) => #<TravelRoute origin: "Ottawa", destination: "London"> TravelRoute.find([["Paris", "Montreal"]]) => [#<TravelRoute origin: "Paris", destination: "Montreal">] TravelRoute.find(["New York", "Las Vegas"], ["New York", "Portland"]) => [ #<TravelRoute origin: "New York", destination: "Las Vegas">, #<TravelRoute origin: "New York", destination: "Portland"> ] TravelRoute.find([["Berlin", "London"], ["Barcelona", "Lisbon"]]) => [ #<TravelRoute origin: "Berlin", destination: "London">, #<TravelRoute origin: "Barcelona", destination: "Lisbon"> ]
NOTE: The returned records are in the same order as the ids you provide. If you want the results to be sorted by database, you can use ActiveRecord::QueryMethods#where
method and provide an explicit ActiveRecord::QueryMethods#order
option. But ActiveRecord::QueryMethods#where
method doesn’t raise ActiveRecord::RecordNotFound
.
Find with lock¶ ↑
Example for find with a lock: Imagine two concurrent transactions: each will read person.visits == 2
, add 1 to it, and save, resulting in two saves of person.visits = 3
. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4
.
Person.transaction do person = Person.lock(true).find(1) person.visits += 1 person.save! end
Variations of find
¶ ↑
Person.where(name: 'Spartacus', rating: 4) # returns a chainable list (which can be empty). Person.find_by(name: 'Spartacus', rating: 4) # returns the first item or nil. Person.find_or_initialize_by(name: 'Spartacus', rating: 4) # returns the first item or returns a new instance (requires you call .save to persist against the database). Person.find_or_create_by(name: 'Spartacus', rating: 4) # returns the first item or creates it and returns it.
Alternatives for find
¶ ↑
Person.where(name: 'Spartacus', rating: 4).exists?(conditions = :none) # returns a boolean indicating if any record with the given conditions exist. Person.where(name: 'Spartacus', rating: 4).select("field1, field2, field3") # returns a chainable list of instances with only the mentioned fields. Person.where(name: 'Spartacus', rating: 4).ids # returns an Array of ids. Person.where(name: 'Spartacus', rating: 4).pluck(:field1, :field2) # returns an Array of the required fields.
Edge Cases¶ ↑
Person.find(37) # raises ActiveRecord::RecordNotFound exception if the record with the given ID does not exist. Person.find([37]) # raises ActiveRecord::RecordNotFound exception if the record with the given ID in the input array does not exist. Person.find(nil) # raises ActiveRecord::RecordNotFound exception if the argument is nil. Person.find([]) # returns an empty array if the argument is an empty array. Person.find # raises ActiveRecord::RecordNotFound exception if the argument is not provided.
Source
# File lib/active_record/relation/finder_methods.rb, line 111 def find_by(arg, *args) where(arg, *args).take end
Finds the first record matching the specified conditions. There is no implied ordering so if order matters, you should specify it yourself.
If no record is found, returns nil
.
Post.find_by name: 'Spartacus', rating: 4 Post.find_by "published_at < ?", 2.weeks.ago
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# File lib/active_record/relation/finder_methods.rb, line 117 def find_by!(arg, *args) where(arg, *args).take! end
Like find_by
, except that if no record is found, raises an ActiveRecord::RecordNotFound
error.
Source
# File lib/active_record/relation/finder_methods.rb, line 160 def find_sole_by(arg, *args) where(arg, *args).sole end
Finds the sole matching record. Raises ActiveRecord::RecordNotFound
if no record is found. Raises ActiveRecord::SoleRecordExceeded
if more than one record is found.
Product.find_sole_by(["price = %?", price])
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# File lib/active_record/relation/finder_methods.rb, line 173 def first(limit = nil) if limit find_nth_with_limit(0, limit) else find_nth 0 end end
Find the first record (or first N records if a parameter is supplied). If no order is defined it will order by primary key.
Person.first # returns the first object fetched by SELECT * FROM people ORDER BY people.id LIMIT 1 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 ORDER BY people.id LIMIT 3
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# File lib/active_record/relation/finder_methods.rb, line 183 def first! first || raise_record_not_found_exception! end
Same as first
but raises ActiveRecord::RecordNotFound
if no record is found. Note that first!
accepts no arguments.
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# File lib/active_record/relation/finder_methods.rb, line 287 def forty_two find_nth 41 end
Find the forty-second record. Also known as accessing “the reddit”. If no order is defined it will order by primary key.
Person.forty_two # returns the forty-second object fetched by SELECT * FROM people Person.offset(3).forty_two # returns the forty-second object from OFFSET 3 (which is OFFSET 44) Person.where(["user_name = :u", { u: user_name }]).forty_two
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# File lib/active_record/relation/finder_methods.rb, line 293 def forty_two! forty_two || raise_record_not_found_exception! end
Same as forty_two
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File lib/active_record/relation/finder_methods.rb, line 255 def fourth find_nth 3 end
Find the fourth record. If no order is defined it will order by primary key.
Person.fourth # returns the fourth object fetched by SELECT * FROM people Person.offset(3).fourth # returns the fourth object from OFFSET 3 (which is OFFSET 6) Person.where(["user_name = :u", { u: user_name }]).fourth
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# File lib/active_record/relation/finder_methods.rb, line 261 def fourth! fourth || raise_record_not_found_exception! end
Same as fourth
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File lib/active_record/relation/finder_methods.rb, line 389 def include?(record) # The existing implementation relies on receiving an Active Record instance as the input parameter named record. # Any non-Active Record object passed to this implementation is guaranteed to return `false`. return false unless record.is_a?(model) if loaded? || offset_value || limit_value || having_clause.any? records.include?(record) else id = if record.class.composite_primary_key? record.class.primary_key.zip(record.id).to_h else record.id end exists?(id) end end
Returns true if the relation contains the given record or false otherwise.
No query is performed if the relation is loaded; the given record is compared to the records in memory. If the relation is unloaded, an efficient existence query is performed, as in exists?
.
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# File lib/active_record/relation/finder_methods.rb, line 202 def last(limit = nil) return find_last(limit) if loaded? || has_limit_or_offset? result = ordered_relation.limit(limit) result = result.reverse_order! limit ? result.reverse : result.first end
Find the last record (or last N records if a parameter is supplied). If no order is defined it will order by primary key.
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>]
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# File lib/active_record/relation/finder_methods.rb, line 213 def last! last || raise_record_not_found_exception! end
Same as last
but raises ActiveRecord::RecordNotFound
if no record is found. Note that last!
accepts no arguments.
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# File lib/active_record/relation/finder_methods.rb, line 223 def second find_nth 1 end
Find the second record. If no order is defined it will order by primary key.
Person.second # returns the second object fetched by SELECT * FROM people Person.offset(3).second # returns the second object from OFFSET 3 (which is OFFSET 4) Person.where(["user_name = :u", { u: user_name }]).second
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# File lib/active_record/relation/finder_methods.rb, line 229 def second! second || raise_record_not_found_exception! end
Same as second
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File lib/active_record/relation/finder_methods.rb, line 319 def second_to_last find_nth_from_last 2 end
Find the second-to-last record. If no order is defined it will order by primary key.
Person.second_to_last # returns the second-to-last object fetched by SELECT * FROM people Person.offset(3).second_to_last # returns the second-to-last object from OFFSET 3 Person.where(["user_name = :u", { u: user_name }]).second_to_last
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# File lib/active_record/relation/finder_methods.rb, line 325 def second_to_last! second_to_last || raise_record_not_found_exception! end
Same as second_to_last
but raises ActiveRecord::RecordNotFound
if no record is found.
Source
# File lib/active_record/relation/finder_methods.rb, line 143 def sole found, undesired = first(2) if found.nil? raise_record_not_found_exception! elsif undesired.nil? found else raise ActiveRecord::SoleRecordExceeded.new(model) end end
Finds the sole matching record. Raises ActiveRecord::RecordNotFound
if no record is found. Raises ActiveRecord::SoleRecordExceeded
if more than one record is found.
Product.where(["price = %?", price]).sole
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# File lib/active_record/relation/finder_methods.rb, line 128 def take(limit = nil) limit ? find_take_with_limit(limit) : find_take end
Gives a record (or N records if a parameter is supplied) without any implied order. The order will depend on the database implementation. If an order is supplied it will be respected.
Person.take # returns an object fetched by SELECT * FROM people LIMIT 1 Person.take(5) # returns 5 objects fetched by SELECT * FROM people LIMIT 5 Person.where(["name LIKE '%?'", name]).take
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# File lib/active_record/relation/finder_methods.rb, line 134 def take! take || raise_record_not_found_exception! end
Same as take
but raises ActiveRecord::RecordNotFound
if no record is found. Note that take!
accepts no arguments.
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# File lib/active_record/relation/finder_methods.rb, line 239 def third find_nth 2 end
Find the third record. If no order is defined it will order by primary key.
Person.third # returns the third object fetched by SELECT * FROM people Person.offset(3).third # returns the third object from OFFSET 3 (which is OFFSET 5) Person.where(["user_name = :u", { u: user_name }]).third
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# File lib/active_record/relation/finder_methods.rb, line 245 def third! third || raise_record_not_found_exception! end
Same as third
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File lib/active_record/relation/finder_methods.rb, line 303 def third_to_last find_nth_from_last 3 end
Find the third-to-last record. If no order is defined it will order by primary key.
Person.third_to_last # returns the third-to-last object fetched by SELECT * FROM people Person.offset(3).third_to_last # returns the third-to-last object from OFFSET 3 Person.where(["user_name = :u", { u: user_name }]).third_to_last
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# File lib/active_record/relation/finder_methods.rb, line 309 def third_to_last! third_to_last || raise_record_not_found_exception! end
Same as third_to_last
but raises ActiveRecord::RecordNotFound
if no record is found.
Private Instance Methods
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# File lib/active_record/relation/finder_methods.rb, line 648 def _order_columns oc = [] oc << model.implicit_order_column if model.implicit_order_column oc << model.query_constraints_list if model.query_constraints_list if model.primary_key && model.query_constraints_list.nil? oc << model.primary_key end oc.flatten.uniq.compact end
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# File lib/active_record/relation/finder_methods.rb, line 457 def apply_join_dependency(eager_loading: group_values.empty?) join_dependency = construct_join_dependency( eager_load_values | includes_values, Arel::Nodes::OuterJoin ) relation = except(:includes, :eager_load, :preload).joins!(join_dependency) if eager_loading && has_limit_or_offset? && !( using_limitable_reflections?(join_dependency.reflections) && using_limitable_reflections?( construct_join_dependency( select_association_list(joins_values).concat( select_association_list(left_outer_joins_values) ), nil ).reflections ) ) relation = skip_query_cache_if_necessary do model.with_connection do |c| c.distinct_relation_for_primary_key(relation) end end end if block_given? yield relation, join_dependency else relation end end
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# File lib/active_record/relation/finder_methods.rb, line 438 def construct_relation_for_exists(conditions) conditions = sanitize_forbidden_attributes(conditions) if distinct_value && offset_value relation = except(:order).limit!(1) else relation = except(:select, :distinct, :order)._select!(ONE_AS_ONE).limit!(1) end case conditions when Array, Hash relation.where!(conditions) unless conditions.empty? else relation.where!(primary_key => conditions) unless conditions == :none end relation end
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# File lib/active_record/relation/finder_methods.rb, line 636 def find_last(limit) limit ? records.last(limit) : records.last end
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# File lib/active_record/relation/finder_methods.rb, line 598 def find_nth(index) @offsets ||= {} @offsets[index] ||= find_nth_with_limit(index, 1).first end
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# File lib/active_record/relation/finder_methods.rb, line 622 def find_nth_from_last(index) if loaded? records[-index] else relation = ordered_relation if relation.order_values.empty? || relation.has_limit_or_offset? relation.records[-index] else relation.reverse_order.offset(index - 1).first end end end
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# File lib/active_record/relation/finder_methods.rb, line 603 def find_nth_with_limit(index, limit) if loaded? records[index, limit] || [] else relation = ordered_relation if limit_value limit = [limit_value - index, limit].min end if limit > 0 relation = relation.offset((offset_value || 0) + index) unless index.zero? relation.limit(limit).to_a else [] end end end
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# File lib/active_record/relation/finder_methods.rb, line 520 def find_one(id) if ActiveRecord::Base === id raise ArgumentError, <<-MSG.squish You are passing an instance of ActiveRecord::Base to `find`. Please pass the id of the object by calling `.id`. MSG end relation = if model.composite_primary_key? where(primary_key.zip(id).to_h) else where(primary_key => id) end record = relation.take raise_record_not_found_exception!(id, 0, 1) unless record record end
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# File lib/active_record/relation/finder_methods.rb, line 541 def find_some(ids) return find_some_ordered(ids) unless order_values.present? relation = where(primary_key => ids) relation = relation.select(table[primary_key]) unless select_values.empty? result = relation.to_a expected_size = if limit_value && ids.size > limit_value limit_value else ids.size end # 11 ids with limit 3, offset 9 should give 2 results. if offset_value && (ids.size - offset_value < expected_size) expected_size = ids.size - offset_value end if result.size == expected_size result else raise_record_not_found_exception!(ids, result.size, expected_size) end end
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# File lib/active_record/relation/finder_methods.rb, line 567 def find_some_ordered(ids) ids = ids.slice(offset_value || 0, limit_value || ids.size) || [] relation = except(:limit, :offset) relation = relation.where(primary_key => ids) relation = relation.select(table[primary_key]) unless select_values.empty? result = relation.records if result.size == ids.size result.in_order_of(:id, ids.map { |id| model.type_for_attribute(primary_key).cast(id) }) else raise_record_not_found_exception!(ids, result.size, ids.size) end end
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# File lib/active_record/relation/finder_methods.rb, line 582 def find_take if loaded? records.first else @take ||= limit(1).records.first end end
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# File lib/active_record/relation/finder_methods.rb, line 590 def find_take_with_limit(limit) if loaded? records.take(limit) else limit(limit).to_a end end
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# File lib/active_record/relation/finder_methods.rb, line 491 def find_with_ids(*ids) raise UnknownPrimaryKey.new(model) if primary_key.nil? expects_array = if model.composite_primary_key? ids.first.first.is_a?(Array) else ids.first.is_a?(Array) end return [] if expects_array && ids.first.empty? ids = ids.first if expects_array ids = ids.compact.uniq model_name = model.name case ids.size when 0 error_message = "Couldn't find #{model_name} without an ID" raise RecordNotFound.new(error_message, model_name, primary_key) when 1 result = find_one(ids.first) expects_array ? [ result ] : result else find_some(ids) end end
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# File lib/active_record/relation/finder_methods.rb, line 640 def ordered_relation if order_values.empty? && (model.implicit_order_column || !model.query_constraints_list.nil? || primary_key) order(_order_columns.map { |column| table[column].asc }) else self end end
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# File lib/active_record/relation/finder_methods.rb, line 487 def using_limitable_reflections?(reflections) reflections.none?(&:collection?) end