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module ActiveRecord
module FinderMethods
# 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)
#
# Note that returned records may not be in the same order as the ids you
# provide since database rows are unordered. Give an explicit <tt>order</tt>
# to ensure 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
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 ording 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
def first(limit = nil)
if limit
if order_values.empty? && primary_key
order(arel_table[primary_key].asc).limit(limit).to_a
else
limit(limit).to_a
end
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 +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 <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
join_dependency = construct_join_dependency_for_association_find
relation = construct_relation_for_association_find(join_dependency)
relation = relation.except(:select, :order).select("1 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, "#{name} Exists", relation.bind_values)
rescue ThrowResult
false
end
protected
def find_with_associations
join_dependency = construct_join_dependency_for_association_find
relation = construct_relation_for_association_find(join_dependency)
rows = connection.select_all(relation, 'SQL', relation.bind_values.dup)
join_dependency.instantiate(rows)
rescue ThrowResult
[]
end
def construct_join_dependency_for_association_find
including = (eager_load_values + includes_values).uniq
ActiveRecord::Associations::JoinDependency.new(@klass, including, [])
end
def construct_relation_for_association_calculations
including = (eager_load_values + includes_values).uniq
join_dependency = ActiveRecord::Associations::JoinDependency.new(@klass, including, arel.froms.first)
relation = except(:includes, :eager_load, :preload)
apply_join_dependency(relation, join_dependency)
end
def construct_relation_for_association_find(join_dependency)
relation = except(:includes, :eager_load, :preload, :select).select(join_dependency.columns)
apply_join_dependency(relation, join_dependency)
end
def apply_join_dependency(relation, join_dependency)
join_dependency.join_associations.each do |association|
relation = association.join_relation(relation)
end
limitable_reflections = using_limitable_reflections?(join_dependency.reflections)
if !limitable_reflections && relation.limit_value
limited_id_condition = construct_limited_ids_condition(relation.except(:select))
relation = relation.where(limited_id_condition)
end
relation = relation.except(:limit, :offset) unless limitable_reflections
relation
end
def construct_limited_ids_condition(relation)
orders = relation.order_values.map { |val| val.presence }.compact
values = @klass.connection.distinct("#{quoted_table_name}.#{primary_key}", orders)
relation = relation.dup.select(values)
id_rows = @klass.connection.select_all(relation.arel, 'SQL', relation.bind_values)
ids_array = id_rows.map {|row| row[primary_key]}
ids_array.empty? ? raise(ThrowResult) : table[primary_key].in(ids_array)
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
unless record
conditions = arel.where_sql
conditions = " [#{conditions}]" if conditions
raise RecordNotFound, "Couldn't find #{@klass.name} with #{primary_key}=#{id}#{conditions}"
end
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
conditions = arel.where_sql
conditions = " [#{conditions}]" if conditions
error = "Couldn't find all #{@klass.name.pluralize} with IDs "
error << "(#{ids.join(", ")})#{conditions} (found #{result.size} results, but was looking for #{expected_size})"
raise RecordNotFound, error
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 ||=
if with_default_scope.order_values.empty? && primary_key
order(arel_table[primary_key].asc).limit(1).to_a.first
else
limit(1).to_a.first
end
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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