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module ActiveRecord
module FinderMethods
ONE_AS_ONE = '1 AS one'
# Find by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]).
# 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+.
#
# 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)
# Person.find([7, 17]) # returns an array for objects with IDs in (7, 17)
# Person.find([1]) # returns an array for the object with ID = 1
# Person.where("administrator = 1").order("created_on DESC").find(1)
#
# <tt>ActiveRecord::RecordNotFound</tt> will be raised if one or more ids are not found.
#
# NOTE: The returned records may not be in the same order as the ids you
# provide since database rows are unordered. You'd need to provide an explicit <tt>order</tt>
# option if you want the results are sorted.
#
# ==== Find with lock
#
# Example for find with a lock: Imagine two concurrent transactions:
# each will read <tt>person.visits == 2</tt>, add 1 to it, and save, resulting
# in two saves of <tt>person.visits = 3</tt>. By locking the row, the second
# transaction has to wait until the first is finished; we get the
# expected <tt>person.visits == 4</tt>.
#
# 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.where(name: 'Spartacus', rating: 4).first_or_initialize
# # returns the first item or returns a new instance (requires you call .save to persist against the database).
#
# Person.where(name: 'Spartacus', rating: 4).first_or_create
# # returns the first item or creates it and returns it, available since Rails 3.2.1.
#
# ==== 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, available since Rails 3.2.1.
#
# Person.where(name: 'Spartacus', rating: 4).pluck(:field1, :field2)
# # returns an Array of the required fields, available since Rails 3.1.
def find(*args)
if block_given?
to_a.find { |*block_args| yield(*block_args) }
else
find_with_ids(*args)
end
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 <tt>nil</tt>.
#
# Post.find_by name: 'Spartacus', rating: 4
# Post.find_by "published_at < ?", 2.weeks.ago
def find_by(*args)
where(*args).take
end
# Like <tt>find_by</tt>, except that if no record is found, raises
# an <tt>ActiveRecord::RecordNotFound</tt> error.
def find_by!(*args)
where(*args).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
def take(limit = nil)
limit ? limit(limit).to_a : find_take
end
# Same as +take+ but raises <tt>ActiveRecord::RecordNotFound</tt> if no record
# is found. Note that <tt>take!</tt> accepts no arguments.
def take!
take or raise RecordNotFound
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
# 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
#
# ==== Rails 3
#
# Person.first # SELECT "people".* FROM "people" LIMIT 1
#
# NOTE: Rails 3 may not order this query by the primary key and the order
# will depend on the database implementation. In order to ensure that behavior,
# use <tt>User.order(:id).first</tt> instead.
#
# ==== Rails 4
#
# Person.first # SELECT "people".* FROM "people" ORDER BY "people"."id" ASC LIMIT 1
#
def first(limit = nil)
if limit
find_first_with_limit(limit)
else
find_first
end
end
# Same as +first+ but raises <tt>ActiveRecord::RecordNotFound</tt> if no record
# is found. Note that <tt>first!</tt> accepts no arguments.
def first!
first or raise RecordNotFound
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>]
def last(limit = nil)
if limit
if order_values.empty? && primary_key
order(arel_table[primary_key].desc).limit(limit).reverse
else
to_a.last(limit)
end
else
find_last
end
end
# Same as +last+ but raises <tt>ActiveRecord::RecordNotFound</tt> if no record
# is found. Note that <tt>last!</tt> accepts no arguments.
def last!
last or raise RecordNotFound
end
# Returns truthy if a record exists in the table that matches the +id+ or
# conditions given, or falsy 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 <tt>'5'</tt>).
# * Array - Finds the record that matches these +find+-style conditions
# (such as <tt>['color = ?', 'red']</tt>).
# * Hash - Finds the record that matches these +find+-style conditions
# (such as <tt>{color: 'red'}</tt>).
# * +false+ - Returns always +false+.
# * No args - Returns +false+ if the table 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 <tt>name =
# 'Jamie'</tt>), since it would be sanitized and then queried against
# the primary key column, like <tt>id = 'name = \'Jamie\''</tt>.
#
# Person.exists?(5)
# Person.exists?('5')
# Person.exists?(['name LIKE ?', "%#{query}%"])
# Person.exists?(name: 'David')
# Person.exists?(false)
# Person.exists?
def exists?(conditions = :none)
conditions = conditions.id if Base === conditions
return false if !conditions
relation = construct_relation_for_association_find(construct_join_dependency)
return false if ActiveRecord::NullRelation === relation
relation = relation.except(:select, :order).select(ONE_AS_ONE).limit(1)
case conditions
when Array, Hash
relation = relation.where(conditions)
else
relation = relation.where(table[primary_key].eq(conditions)) if conditions != :none
end
connection.select_value(relation.arel, "#{name} Exists", relation.bind_values)
end
# This method is called whenever no records are found with either a single
# id or multiple ids and raises a +ActiveRecord::RecordNotFound+ exception.
#
# The error message is different depending on whether a single id or
# multiple ids are provided. If multiple ids are provided, then the number
# of results obtained should be provided in the +result_size+ argument and
# the expected number of results should be provided in the +expected_size+
# argument.
def raise_record_not_found_exception!(ids, result_size, expected_size) #:nodoc:
conditions = arel.where_sql
conditions = " [#{conditions}]" if conditions
if Array(ids).size == 1
error = "Couldn't find #{@klass.name} with #{primary_key}=#{ids}#{conditions}"
else
error = "Couldn't find all #{@klass.name.pluralize} with IDs "
error << "(#{ids.join(", ")})#{conditions} (found #{result_size} results, but was looking for #{expected_size})"
end
raise RecordNotFound, error
end
protected
def find_with_associations
join_dependency = construct_join_dependency
relation = construct_relation_for_association_find(join_dependency)
if ActiveRecord::NullRelation === relation
[]
else
rows = connection.select_all(relation, 'SQL', relation.bind_values.dup)
join_dependency.instantiate(rows)
end
end
def construct_join_dependency(joins = [])
including = (eager_load_values + includes_values).uniq
ActiveRecord::Associations::JoinDependency.new(@klass, including, joins)
end
def construct_relation_for_association_calculations
apply_join_dependency(self, construct_join_dependency(arel.froms.first))
end
def construct_relation_for_association_find(join_dependency)
relation = except(:select).select(join_dependency.columns)
apply_join_dependency(relation, join_dependency)
end
def apply_join_dependency(relation, join_dependency)
relation = relation.except(:includes, :eager_load, :preload)
relation = join_dependency.join_relation(relation)
if using_limitable_reflections?(join_dependency.reflections)
relation
else
if relation.limit_value
limited_ids = limited_ids_for(relation)
limited_ids.empty? ? relation.none! : relation.where!(table[primary_key].in(limited_ids))
end
relation.except(:limit, :offset)
end
end
def limited_ids_for(relation)
values = @klass.connection.columns_for_distinct(
"#{quoted_table_name}.#{quoted_primary_key}", relation.order_values)
relation = relation.except(:select).select(values).distinct!
id_rows = @klass.connection.select_all(relation.arel, 'SQL', relation.bind_values)
id_rows.map {|row| row[primary_key]}
end
def find_with_ids(*ids)
expects_array = ids.first.kind_of?(Array)
return ids.first if expects_array && ids.first.empty?
ids = ids.flatten.compact.uniq
case ids.size
when 0
raise RecordNotFound, "Couldn't find #{@klass.name} without an ID"
when 1
result = find_one(ids.first)
expects_array ? [ result ] : result
else
find_some(ids)
end
end
def find_one(id)
id = id.id if ActiveRecord::Base === id
column = columns_hash[primary_key]
substitute = connection.substitute_at(column, bind_values.length)
relation = where(table[primary_key].eq(substitute))
relation.bind_values += [[column, id]]
record = relation.take
raise_record_not_found_exception!(id, 0, 1) unless record
record
end
def find_some(ids)
result = where(table[primary_key].in(ids)).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
def find_take
if loaded?
@records.first
else
@take ||= limit(1).to_a.first
end
end
def find_first
if loaded?
@records.first
else
@first ||= find_first_with_limit(1).first
end
end
def find_first_with_limit(limit)
if order_values.empty? && primary_key
order(arel_table[primary_key].asc).limit(limit).to_a
else
limit(limit).to_a
end
end
def find_last
if loaded?
@records.last
else
@last ||=
if offset_value || limit_value
to_a.last
else
reverse_order.limit(1).to_a.first
end
end
end
def using_limitable_reflections?(reflections)
reflections.none? { |r| r.collection? }
end
end
end
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