Module: ActiveRecord::QueryMethods
Relationships & Source Files | |
Namespace Children | |
Classes:
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Extension / Inclusion / Inheritance Descendants | |
Included In:
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Super Chains via Extension / Inclusion / Inheritance | |
Instance Chain:
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Defined in: | activerecord/lib/active_record/relation/query_methods.rb |
Constant Summary
-
FROZEN_EMPTY_ARRAY =
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 140[].freeze
-
FROZEN_EMPTY_HASH =
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 141{}.freeze
-
STRUCTURAL_VALUE_METHODS =
Internal use only
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 2031( Relation::VALUE_METHODS - [:extending, :where, :having, :unscope, :references, :annotate, :optimizer_hints] ).freeze
-
VALID_DIRECTIONS =
Internal use only
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1859[:asc, :desc, :ASC, :DESC, "asc", "desc", "ASC", "DESC"].to_set
-
VALID_UNSCOPING_VALUES =
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 667Set.new([:where, :select, :group, :order, :lock, :limit, :offset, :joins, :left_outer_joins, :annotate, :includes, :eager_load, :preload, :from, :readonly, :having, :optimizer_hints])
Instance Attribute Summary
- #null_relation? ⇒ Boolean readonly Internal use only
Instance Method Summary
-
#and(other)
Returns a new relation, which is the logical intersection of this relation and the one passed as an argument.
-
#annotate(*args)
Adds an SQL comment to queries generated from this relation.
-
#create_with(value)
Sets attributes to be used when creating new records from a relation object.
-
#distinct(value = true)
Specifies whether the records should be unique or not.
-
#eager_load(*args)
Specify associations
args
to be eager loaded using aLEFT OUTER JOIN
. -
#excluding(*records)
(also: #without)
Excludes the specified record (or collection of records) from the resulting relation.
-
#extending(*modules, &block)
Used to extend a scope with additional methods, either through a module or through a block provided.
- #extensions
-
#extract_associated(association)
Extracts a named
association
from the relation. -
#from(value, subquery_name = nil)
Specifies the table from which the records will be fetched.
-
#group(*args)
Allows to specify a group attribute:
-
#having(opts, *rest)
Allows to specify a HAVING clause.
-
#in_order_of(column, values)
Allows to specify an order by a specific set of values.
-
#includes(*args)
Specify associations
args
to be eager loaded to prevent N + 1 queries. -
#invert_where
Allows you to invert an entire where clause instead of manually applying conditions.
-
#joins(*args)
Performs JOINs on
args
. -
#left_joins(*args)
Alias for #left_outer_joins.
-
#left_outer_joins(*args)
(also: #left_joins)
Performs LEFT OUTER JOINs on
args
: -
#limit(value)
Specifies a limit for the number of records to retrieve.
-
#lock(locks = true)
Specifies locking settings (default to
true
). -
#none
Returns a chainable relation with zero records.
-
#offset(value)
Specifies the number of rows to skip before returning rows.
-
#optimizer_hints(*args)
Specify optimizer hints to be used in the SELECT statement.
-
#or(other)
Returns a new relation, which is the logical union of this relation and the one passed as an argument.
-
#order(*args)
Applies an
ORDER BY
clause to a query. -
#preload(*args)
Specify associations
args
to be eager loaded using separate queries. -
#readonly(value = true)
Mark a relation as readonly.
-
#references(*table_names)
Use to indicate that the given
table_names
are referenced by an SQL string, and should therefore beJOIN
ed in any query rather than loaded separately. -
#regroup(*args)
Allows you to change a previously set group statement.
-
#reorder(*args)
Replaces any existing order defined on the relation with the specified order.
-
#reselect(*args)
Allows you to change a previously set select statement.
-
#reverse_order
Reverse the existing order clause on the relation.
-
#rewhere(conditions)
Allows you to change a previously set where condition for a given attribute, instead of appending to that condition.
-
#select(*fields)
Works in two unique ways.
-
#strict_loading(value = true)
Sets the returned relation to strict_loading mode.
- #structurally_compatible?(other) ⇒ Boolean
-
#uniq!(name)
Deduplicate multiple values.
-
#unscope(*args)
Removes an unwanted relation that is already defined on a chain of relations.
-
#where(*args)
Returns a new relation, which is the result of filtering the current relation according to the conditions in the arguments.
-
#with(*args)
Add a Common Table Expression (CTE) that you can then reference within another SELECT statement.
-
#without(*records)
Alias for #excluding.
- #async! protected
-
#build_having_clause(opts, rest = [])
protected
Alias for #build_where_clause.
- #arel_column(field) private
- #arel_columns(columns) private
- #assert_mutability! private
- #async private
- #build_arel(aliases = nil) private
- #build_case_for_value_position(column, values) private
- #build_cast_value(name, value) private
- #build_from private
- #build_join_buckets private
- #build_join_dependencies private
- #build_joins(join_sources, aliases = nil) private
- #build_order(arel) private
- #build_select(arel) private
- #build_with(arel) private
- #build_with_join_node(name, kind = Arel::Nodes::InnerJoin) private
- #build_with_value_from_hash(hash) private
-
#check_if_method_has_arguments!(method_name, args, message = nil)
private
Checks to make sure that the arguments are not blank.
- #column_references(order_args) private
- #does_not_support_reverse?(order) ⇒ Boolean private
- #each_join_dependencies(join_dependencies = build_join_dependencies, &block) private
- #lookup_table_klass_from_join_dependencies(table_name) private
- #order_column(field) private
- #preprocess_order_args(order_args) private
- #process_select_args(fields) private
- #resolve_arel_attributes(attrs) private
- #reverse_sql_order(order_query) private
- #sanitize_order_arguments(order_args) private
- #select_association_list(associations, stashed_joins = nil) private
- #select_named_joins(join_names, stashed_joins = nil, &block) private
- #table_name_matches?(from) ⇒ Boolean private
- #transform_select_hash_values(fields) private
- #validate_order_args(args) private
- #_select!(*fields) Internal use only
- #and!(other) Internal use only
-
#annotate!(*args)
Internal use only
Like #annotate, but modifies relation in place.
-
#arel(aliases = nil)
Internal use only
Returns the
::Arel
object associated with the relation. - #construct_join_dependency(associations, join_type) Internal use only
- #create_with!(value) Internal use only
-
#distinct!(value = true)
Internal use only
Like #distinct, but modifies relation in place.
- #eager_load!(*args) Internal use only
- #excluding!(records) Internal use only
- #extending!(*modules, &block) Internal use only
- #from!(value, subquery_name = nil) Internal use only
- #group!(*args) Internal use only
- #having!(opts, *rest) Internal use only
- #includes!(*args) Internal use only
- #invert_where! Internal use only
- #joins!(*args) Internal use only
- #left_outer_joins!(*args) Internal use only
- #limit!(value) Internal use only
- #lock!(locks = true) Internal use only
- #none! Internal use only
- #offset!(value) Internal use only
- #optimizer_hints!(*args) Internal use only
- #or!(other) Internal use only
-
#order!(*args)
Internal use only
Same as #order but operates on relation in-place instead of copying.
- #preload!(*args) Internal use only
- #readonly!(value = true) Internal use only
- #references!(*table_names) Internal use only
-
#regroup!(*args)
Internal use only
Same as #regroup but operates on relation in-place instead of copying.
-
#reorder!(*args)
Internal use only
Same as #reorder but operates on relation in-place instead of copying.
-
#reselect!(*args)
Internal use only
Same as #reselect but operates on relation in-place instead of copying.
- #reverse_order! Internal use only
- #skip_preloading! Internal use only
- #skip_query_cache!(value = true) Internal use only
- #strict_loading!(value = true) Internal use only
- #unscope!(*args) Internal use only
- #where!(opts, *rest) Internal use only
-
#with!(*args)
Internal use only
Like #with, but modifies relation in place.
- #build_subquery(subquery_alias, select_value) protected Internal use only
- #build_where_clause(opts, rest = []) (also: #build_having_clause) protected Internal use only
- #structurally_incompatible_values_for(other) private Internal use only
::ActiveModel::ForbiddenAttributesProtection
- Included
Instance Attribute Details
#null_relation? ⇒ Boolean
(readonly)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1192
def null_relation? # :nodoc: @none end
Instance Method Details
#_select!(*fields)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 405
def _select!(*fields) # :nodoc: self.select_values |= fields self end
#and(other)
Returns a new relation, which is the logical intersection of this relation and the one passed as an argument.
The two relations must be structurally compatible: they must be scoping the same model, and they must differ only by #where (if no #group has been defined) or #having (if a #group is present).
Post.where(id: [1, 2]).and(Post.where(id: [2, 3]))
# SELECT `posts`.* FROM `posts` WHERE `posts`.`id` IN (1, 2) AND `posts`.`id` IN (2, 3)
#and!(other)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1042
def and!(other) # :nodoc: incompatible_values = structurally_incompatible_values_for(other) unless incompatible_values.empty? raise ArgumentError, "Relation passed to #and must be structurally compatible. Incompatible values: #{incompatible_values}" end self.where_clause |= other.where_clause self.having_clause |= other.having_clause self.references_values |= other.references_values self end
#annotate(*args)
Adds an SQL comment to queries generated from this relation. For example:
User.annotate("selecting user names").select(:name)
# SELECT "users"."name" FROM "users" /* selecting user names */
User.annotate("selecting", "user", "names").select(:name)
# SELECT "users"."name" FROM "users" /* selecting */ /* user */ /* names */
The SQL block comment delimiters, “/*” and “*/”, will be added automatically.
Some escaping is performed, however untrusted user input should not be used.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1428
def annotate(*args) check_if_method_has_arguments!(__callee__, args) spawn.annotate!(*args) end
#annotate!(*args)
Like #annotate, but modifies relation in place.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1434
def annotate!(*args) # :nodoc: self.annotate_values += args self end
#arel(aliases = nil)
Returns the ::Arel
object associated with the relation.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1489
def arel(aliases = nil) # :nodoc: @arel ||= build_arel(aliases) end
#arel_column(field) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1792
def arel_column(field) field = klass.attribute_aliases[field] || field from = from_clause.name || from_clause.value if klass.columns_hash.key?(field) && (!from || table_name_matches?(from)) table[field] elsif field.match?(/\A\w\.\w\z/) table, column = field.split(".") predicate_builder.resolve_arel_attribute(table, column) do lookup_table_klass_from_join_dependencies(table) end else yield field end end
#arel_columns(columns) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1775
def arel_columns(columns) columns.flat_map do |field| case field when Symbol arel_column(field.to_s) do |attr_name| connection.quote_table_name(attr_name) end when String arel_column(field, &:itself) when Proc field.call else field end end end
#assert_mutability! (private)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1573
def assert_mutability! raise ImmutableRelation if @loaded raise ImmutableRelation if defined?(@arel) && @arel end
#async (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1545
def async spawn.async! end
#async! (protected)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1539
def async! @async = true self end
#build_arel(aliases = nil) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1578
def build_arel(aliases = nil) arel = Arel::SelectManager.new(table) build_joins(arel.join_sources, aliases) arel.where(where_clause.ast) unless where_clause.empty? arel.having(having_clause.ast) unless having_clause.empty? arel.take(build_cast_value("LIMIT", connection.sanitize_limit(limit_value))) if limit_value arel.skip(build_cast_value("OFFSET", offset_value.to_i)) if offset_value arel.group(*arel_columns(group_values.uniq)) unless group_values.empty? build_order(arel) build_with(arel) build_select(arel) arel.optimizer_hints(*optimizer_hints_values) unless optimizer_hints_values.empty? arel.distinct(distinct_value) arel.from(build_from) unless from_clause.empty? arel.lock(lock_value) if lock_value unless annotate_values.empty? annotates = annotate_values annotates = annotates.uniq if annotates.size > 1 arel.comment(*annotates) end arel end
#build_case_for_value_position(column, values) (private)
[ GitHub ]#build_cast_value(name, value) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1607
def build_cast_value(name, value) ActiveModel::Attribute.with_cast_value(name, value, Type.default_value) end
#build_from (private)
[ GitHub ]#build_having_clause(opts, rest = []) (protected)
Alias for #build_where_clause.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1537
alias :build_having_clause :build_where_clause
#build_join_buckets (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1653
def build_join_buckets buckets = Hash.new { |h, k| h[k] = [] } unless left_outer_joins_values.empty? stashed_left_joins = [] left_joins = select_named_joins(left_outer_joins_values, stashed_left_joins) do |left_join| if left_join.is_a?(CTEJoin) buckets[:join_node] << build_with_join_node(left_join.name, Arel::Nodes::OuterJoin) else raise ArgumentError, "only Hash, Symbol and Array are allowed" end end if joins_values.empty? buckets[:named_join] = left_joins buckets[:stashed_join] = stashed_left_joins return buckets, Arel::Nodes::OuterJoin else stashed_left_joins.unshift construct_join_dependency(left_joins, Arel::Nodes::OuterJoin) end end joins = joins_values.dup if joins.last.is_a?(ActiveRecord::Associations::JoinDependency) stashed_eager_load = joins.pop if joins.last.base_klass == klass end joins.each_with_index do |join, i| joins[i] = Arel::Nodes::StringJoin.new(Arel.sql(join.strip)) if join.is_a?(String) end while joins.first.is_a?(Arel::Nodes::Join) join_node = joins.shift if !join_node.is_a?(Arel::Nodes::LeadingJoin) && (stashed_eager_load || stashed_left_joins) buckets[:join_node] << join_node else buckets[:leading_join] << join_node end end buckets[:named_join] = select_named_joins(joins, buckets[:stashed_join]) do |join| if join.is_a?(Arel::Nodes::Join) buckets[:join_node] << join elsif join.is_a?(CTEJoin) buckets[:join_node] << build_with_join_node(join.name) else raise "unknown class: %s" % join.class.name end end buckets[:stashed_join].concat stashed_left_joins if stashed_left_joins buckets[:stashed_join] << stashed_eager_load if stashed_eager_load return buckets, Arel::Nodes::InnerJoin end
#build_join_dependencies (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1562
def build_join_dependencies joins = joins_values | left_outer_joins_values joins |= eager_load_values unless eager_load_values.empty? joins |= includes_values unless includes_values.empty? join_dependencies = [] join_dependencies.unshift construct_join_dependency( select_named_joins(joins, join_dependencies), nil ) end
#build_joins(join_sources, aliases = nil) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1709
def build_joins(join_sources, aliases = nil) return join_sources if joins_values.empty? && left_outer_joins_values.empty? buckets, join_type = build_join_buckets named_joins = buckets[:named_join] stashed_joins = buckets[:stashed_join] leading_joins = buckets[:leading_join] join_nodes = buckets[:join_node] join_sources.concat(leading_joins) unless leading_joins.empty? unless named_joins.empty? && stashed_joins.empty? alias_tracker = alias_tracker(leading_joins + join_nodes, aliases) join_dependency = construct_join_dependency(named_joins, join_type) join_sources.concat(join_dependency.join_constraints(stashed_joins, alias_tracker, references_values)) end join_sources.concat(join_nodes) unless join_nodes.empty? join_sources end
#build_order(arel) (private)
[ GitHub ]#build_select(arel) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1731
def build_select(arel) if select_values.any? arel.project(*arel_columns(select_values)) elsif klass.ignored_columns.any? || klass.enumerate_columns_in_select_statements arel.project(*klass.column_names.map { |field| table[field] }) else arel.project(table[Arel.star]) end end
#build_subquery(subquery_alias, select_value) (protected)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1500
def build_subquery(subquery_alias, select_value) # :nodoc: subquery = except(:optimizer_hints).arel.as(subquery_alias) Arel::SelectManager.new(subquery).project(select_value).tap do |arel| arel.optimizer_hints(*optimizer_hints_values) unless optimizer_hints_values.empty? end end
#build_where_clause(opts, rest = []) (protected) Also known as: #build_having_clause
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1508
def build_where_clause(opts, rest = []) # :nodoc: opts = sanitize_forbidden_attributes(opts) case opts when String, Array parts = [klass.sanitize_sql(rest.empty? ? opts : [opts, *rest])] when Hash opts = opts.transform_keys do |key| if key.is_a?(Array) key.map { |k| klass.attribute_aliases[k.to_s] || k.to_s } else key = key.to_s klass.attribute_aliases[key] || key end end references = PredicateBuilder.references(opts) self.references_values |= references unless references.empty? parts = predicate_builder.build_from_hash(opts) do |table_name| lookup_table_klass_from_join_dependencies(table_name) end when Arel::Nodes::Node parts = [opts] else raise ArgumentError, "Unsupported argument type: #{opts} (#{opts.class})" end Relation::WhereClause.new(parts) end
#build_with(arel) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1741
def build_with(arel) return if with_values.empty? with_statements = with_values.map do |with_value| raise ArgumentError, "Unsupported argument type: #{with_value} #{with_value.class}" unless with_value.is_a?(Hash) build_with_value_from_hash(with_value) end arel.with(with_statements) end
#build_with_join_node(name, kind = Arel::Nodes::InnerJoin) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1767
def build_with_join_node(name, kind = Arel::Nodes::InnerJoin) with_table = Arel::Table.new(name) table.join(with_table, kind).on( with_table[klass.model_name.to_s.foreign_key].eq(table[klass.primary_key]) ).join_sources.first end
#build_with_value_from_hash(hash) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1753
def build_with_value_from_hash(hash) hash.map do |name, value| expression = case value when Arel::Nodes::SqlLiteral then Arel::Nodes::Grouping.new(value) when ActiveRecord::Relation then value.arel when Arel::SelectManager then value else raise ArgumentError, "Unsupported argument type: `#{value}` #{value.class}" end Arel::Nodes::TableAlias.new(expression, name) end end
#check_if_method_has_arguments!(method_name, args, message = nil) (private)
Checks to make sure that the arguments are not blank. Note that if some blank-like object were initially passed into the query method, then this method will not raise an error.
Example:
Post.references() # raises an error
Post.references([]) # does not raise an error
This particular method should be called with a method_name (__callee__) and the args passed into that method as an input. For example:
def references(*args)
check_if_method_has_arguments!(__callee__, args)
#...
end
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1985
def check_if_method_has_arguments!(method_name, args, = nil) if args.blank? raise ArgumentError, || "The method .#{method_name}() must contain arguments." else yield args if block_given? args.flatten! args.compact_blank! end end
#column_references(order_args) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1911
def column_references(order_args) references = order_args.flat_map do |arg| case arg when String, Symbol arg when Hash arg.keys.map do |key| key if key.is_a?(String) || key.is_a?(Symbol) end end end references.map! { |arg| arg =~ /^\W?(\w+)\W?\./ && $1 }.compact! references end
#construct_join_dependency(associations, join_type)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1493
def construct_join_dependency(associations, join_type) # :nodoc: ActiveRecord::Associations::JoinDependency.new( klass, table, associations, join_type ) end
#create_with(value)
Sets attributes to be used when creating new records from a relation object.
users = User.where(name: 'Oscar')
users.new.name # => 'Oscar'
users = users.create_with(name: 'DHH')
users.new.name # => 'DHH'
You can pass nil
to #create_with
to reset attributes:
users = users.create_with(nil)
users.new.name # => 'Oscar'
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1245
def create_with(value) spawn.create_with!(value) end
#create_with!(value)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1249
def create_with!(value) # :nodoc: if value value = sanitize_forbidden_attributes(value) self.create_with_value = create_with_value.merge(value) else self.create_with_value = FROZEN_EMPTY_HASH end self end
#distinct(value = true)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1309
def distinct(value = true) spawn.distinct!(value) end
#distinct!(value = true)
Like #distinct, but modifies relation in place.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1314
def distinct!(value = true) # :nodoc: self.distinct_value = value self end
#does_not_support_reverse?(order) ⇒ Boolean
(private)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1843
def does_not_support_reverse?(order) # Account for String subclasses like Arel::Nodes::SqlLiteral that # override methods like #count. order = String.new(order) unless order.instance_of?(String) # Uses SQL function with multiple arguments. (order.include?(",") && order.split(",").find { |section| section.count("(") != section.count(")") }) || # Uses "nulls first" like construction. /\bnulls\s+(?:first|last)\b/i.match?(order) end
#each_join_dependencies(join_dependencies = build_join_dependencies, &block) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1556
def each_join_dependencies(join_dependencies = build_join_dependencies, &block) join_dependencies.each do |join_dependency| join_dependency.each(&block) end end
#eager_load(*args)
Specify associations args
to be eager loaded using a LEFT OUTER JOIN
. Performs a single query joining all specified associations. For example:
users = User.eager_load(:address).limit(5)
users.each do |user|
user.address.city
end
# SELECT "users"."id" AS t0_r0, "users"."name" AS t0_r1, ... FROM "users"
# LEFT OUTER JOIN "addresses" ON "addresses"."id" = "users"."address_id"
# LIMIT 5
Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a single joined query.
Loading multiple and nested associations is possible using Hashes and Arrays, similar to #includes:
User.eager_load(:address, friends: [:address, :followers])
# SELECT "users"."id" AS t0_r0, "users"."name" AS t0_r1, ... FROM "users"
# LEFT OUTER JOIN "addresses" ON "addresses"."id" = "users"."address_id"
# LEFT OUTER JOIN "friends" ON "friends"."user_id" = "users"."id"
# ...
NOTE: Loading the associations in a join can result in many rows that contain redundant data and it performs poorly at scale.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 267
def eager_load(*args) check_if_method_has_arguments!(__callee__, args) spawn.eager_load!(*args) end
#eager_load!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 272
def eager_load!(*args) # :nodoc: self.eager_load_values |= args self end
#excluding(*records) Also known as: #without
Excludes the specified record (or collection of records) from the resulting relation. For example:
Post.excluding(post)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" != 1
Post.excluding(post_one, post_two)
# SELECT "posts".* FROM "posts" WHERE "posts"."id" NOT IN (1, 2)
This can also be called on associations. As with the above example, either a single record of collection thereof may be specified:
post = Post.find(1)
comment = Comment.find(2)
post.comments.excluding(comment)
# SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1 AND "comments"."id" != 2
This is short-hand for .where.not(id: post.id)
and .where.not(id: [post_one.id, post_two.id])
.
An ArgumentError
will be raised if either no records are specified, or if any of the records in the collection (if a collection is passed in) are not instances of the same model that the relation is scoping.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1470
def excluding(*records) records.flatten!(1) records.compact! unless records.all?(klass) raise ArgumentError, "You must only pass a single or collection of #{klass.name} objects to ##{__callee__}." end spawn.excluding!(records) end
#excluding!(records)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1482
def excluding!(records) # :nodoc: predicates = [ predicate_builder[primary_key, records].invert ] self.where_clause += Relation::WhereClause.new(predicates) self end
#extending(*modules, &block)
Used to extend a scope with additional methods, either through a module or through a block provided.
The object returned is a relation, which can be further extended.
Using a Module
module Pagination
def page(number)
# pagination code goes here
end
end
scope = Model.all.extending(Pagination)
scope.page(params[:page])
You can also pass a list of modules:
scope = Model.all.extending(Pagination, SomethingElse)
Using a Block
scope = Model.all.extending do
def page(number)
# pagination code goes here
end
end
scope.page(params[:page])
You can also use a block and a module list:
scope = Model.all.extending(Pagination) do
def per_page(number)
# pagination code goes here
end
end
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1355
def extending(*modules, &block) if modules.any? || block spawn.extending!(*modules, &block) else self end end
#extending!(*modules, &block)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1363
def extending!(*modules, &block) # :nodoc: modules << Module.new(&block) if block modules.flatten! self.extending_values += modules extend(*extending_values) if extending_values.any? self end
#extensions
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 166
alias extensions extending_values
#extract_associated(association)
Extracts a named association
from the relation. The named association is first preloaded, then the individual association records are collected from the relation. Like so:
account.memberships.extract_associated(:user)
# => Returns collection of User records
This is short-hand for:
account.memberships.preload(:user).collect(&:user)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 318
def extract_associated(association) preload(association).collect(&association) end
#from(value, subquery_name = nil)
Specifies the table from which the records will be fetched. For example:
Topic.select('title').from('posts')
# SELECT title FROM posts
Can accept other relation objects. For example:
Topic.select('title').from(Topic.approved)
# SELECT title FROM (SELECT * FROM topics WHERE approved = 't') subquery
Passing a second argument (string or symbol), creates the alias for the SQL from clause. Otherwise the alias “subquery” is used:
Topic.select('a.title').from(Topic.approved, :a)
# SELECT a.title FROM (SELECT * FROM topics WHERE approved = 't') a
It does not add multiple arguments to the SQL from clause. The last from
chained is the one used:
Topic.select('title').from(Topic.approved).from(Topic.inactive)
# SELECT title FROM (SELECT topics.* FROM topics WHERE topics.active = 'f') subquery
For multiple arguments for the SQL from clause, you can pass a string with the exact elements in the SQL from list:
color = "red"
Color
.from("colors c, JSONB_ARRAY_ELEMENTS(colored_things) AS colorvalues(colorvalue)")
.where("colorvalue->>'color' = ?", color)
.select("c.*").to_a
# SELECT c.*
# FROM colors c, JSONB_ARRAY_ELEMENTS(colored_things) AS colorvalues(colorvalue)
# WHERE (colorvalue->>'color' = 'red')
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1290
def from(value, subquery_name = nil) spawn.from!(value, subquery_name) end
#from!(value, subquery_name = nil)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1294
def from!(value, subquery_name = nil) # :nodoc: self.from_clause = Relation::FromClause.new(value, subquery_name) self end
#group(*args)
Allows to specify a group attribute:
User.group(:name)
# SELECT "users".* FROM "users" GROUP BY name
Returns an array with distinct records based on the group
attribute:
User.select([:id, :name])
# => [#<User id: 1, name: "Oscar">, #<User id: 2, name: "Oscar">, #<User id: 3, name: "Foo">]
User.group(:name)
# => [#<User id: 3, name: "Foo", ...>, #<User id: 2, name: "Oscar", ...>]
User.group('name AS grouped_name, age')
# => [#<User id: 3, name: "Foo", age: 21, ...>, #<User id: 2, name: "Oscar", age: 21, ...>, #<User id: 5, name: "Foo", age: 23, ...>]
Passing in an array of attributes to group by is also supported.
User.select([:id, :first_name]).group(:id, :first_name).first(3)
# => [#<User id: 1, first_name: "Bill">, #<User id: 2, first_name: "Earl">, #<User id: 3, first_name: "Beto">]
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 512
def group(*args) check_if_method_has_arguments!(__callee__, args) spawn.group!(*args) end
#group!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 517
def group!(*args) # :nodoc: self.group_values += args self end
#having(opts, *rest)
Allows to specify a HAVING clause. Note that you can’t use HAVING without also specifying a GROUP clause.
Order.having('SUM(price) > 30').group('user_id')
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1096
def having(opts, *rest) opts.blank? ? self : spawn.having!(opts, *rest) end
#having!(opts, *rest)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1100
def having!(opts, *rest) # :nodoc: self.having_clause += build_having_clause(opts, rest) self end
#in_order_of(column, values)
Allows to specify an order by a specific set of values.
User.in_order_of(:id, [1, 5, 3])
# SELECT "users".* FROM "users"
# WHERE "users"."id" IN (1, 5, 3)
# ORDER BY CASE
# WHEN "users"."id" = 1 THEN 1
# WHEN "users"."id" = 5 THEN 2
# WHEN "users"."id" = 3 THEN 3
# END ASC
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 620
def in_order_of(column, values) klass.disallow_raw_sql!([column], permit: connection.column_name_with_order_matcher) return spawn.none! if values.empty? references = column_references([column]) self.references_values |= references unless references.empty? values = values.map { |value| type_caster.type_cast_for_database(column, value) } arel_column = column.is_a?(Arel::Nodes::SqlLiteral) ? column : order_column(column.to_s) where_clause = if values.include?(nil) arel_column.in(values.compact).or(arel_column.eq(nil)) else arel_column.in(values) end spawn .order!(build_case_for_value_position(arel_column, values)) .where!(where_clause) end
#includes(*args)
Specify associations args
to be eager loaded to prevent N + 1 queries. A separate query is performed for each association, unless a join is required by conditions.
For example:
users = User.includes(:address).limit(5)
users.each do |user|
user.address.city
end
# SELECT "users".* FROM "users" LIMIT 5
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a single query.
Loading the associations in a separate query will often result in a performance improvement over a simple join, as a join can result in many rows that contain redundant data and it performs poorly at scale.
You can also specify multiple associations. Each association will result in an additional query:
User.includes(:address, :friends).to_a
# SELECT "users".* FROM "users"
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
# SELECT "friends".* FROM "friends" WHERE "friends"."user_id" IN (1,2,3,4,5)
Loading nested associations is possible using a ::Hash
:
User.includes(:address, friends: [:address, :followers])
Conditions
If you want to add string conditions to your included models, you’ll have to explicitly reference them. For example:
User.includes(:posts).where('posts.name = ?', 'example').to_a
Will throw an error, but this will work:
User.includes(:posts).where('posts.name = ?', 'example').references(:posts).to_a
# SELECT "users"."id" AS t0_r0, ... FROM "users"
# LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
# WHERE "posts"."name" = ? [["name", "example"]]
As the LEFT OUTER JOIN
already contains the posts, the second query for the posts is no longer performed.
Note that #includes
works with association names while #references needs the actual table name.
If you pass the conditions via a ::Hash
, you don’t need to call #references explicitly, as #where references the tables for you. For example, this will work correctly:
User.includes(:posts).where(posts: { name: 'example' })
NOTE: Conditions affect both sides of an association. For example, the above code will return only users that have a post named “example”, and will only include posts named “example”, even when a matching user has other additional posts.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 231
def includes(*args) check_if_method_has_arguments!(__callee__, args) spawn.includes!(*args) end
#includes!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 236
def includes!(*args) # :nodoc: self.includes_values |= args self end
#invert_where
Allows you to invert an entire where clause instead of manually applying conditions.
class User
scope :active, -> { where(accepted: true, locked: false) }
end
User.where(accepted: true)
# WHERE `accepted` = 1
User.where(accepted: true).invert_where
# WHERE `accepted` != 1
User.active
# WHERE `accepted` = 1 AND `locked` = 0
User.active.invert_where
# WHERE NOT (`accepted` = 1 AND `locked` = 0)
Be careful because this inverts all conditions before invert_where
call.
class User
scope :active, -> { where(accepted: true, locked: false) }
scope :inactive, -> { active.invert_where } # Do not attempt it
end
# It also inverts `where(role: 'admin')` unexpectedly.
User.where(role: 'admin').inactive
# WHERE NOT (`role` = 'admin' AND `accepted` = 1 AND `locked` = 0)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1000
def invert_where spawn.invert_where! end
#invert_where!
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1004
def invert_where! # :nodoc: self.where_clause = where_clause.invert self end
#joins(*args)
Performs JOINs on args
. The given symbol(s) should match the name of the association(s).
User.joins(:posts)
# SELECT "users".*
# FROM "users"
# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"
Multiple joins:
User.joins(:posts, :account)
# SELECT "users".*
# FROM "users"
# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"
# INNER JOIN "accounts" ON "accounts"."id" = "users"."account_id"
Nested joins:
User.joins(posts: [:comments])
# SELECT "users".*
# FROM "users"
# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"
# INNER JOIN "comments" ON "comments"."post_id" = "posts"."id"
You can use strings in order to customize your joins:
User.joins("LEFT JOIN bookmarks ON bookmarks.bookmarkable_type = 'Post' AND bookmarks.user_id = users.id")
# SELECT "users".* FROM "users" LEFT JOIN bookmarks ON bookmarks.bookmarkable_type = 'Post' AND bookmarks.user_id = users.id
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 767
def joins(*args) check_if_method_has_arguments!(__callee__, args) spawn.joins!(*args) end
#joins!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 772
def joins!(*args) # :nodoc: self.joins_values |= args self end
#left_joins(*args)
Alias for #left_outer_joins.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 786
alias :left_joins :left_outer_joins
#left_outer_joins(*args) Also known as: #left_joins
Performs LEFT OUTER JOINs on args
:
User.left_outer_joins(:posts)
# SELECT "users".* FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 782
def left_outer_joins(*args) check_if_method_has_arguments!(__callee__, args) spawn.left_outer_joins!(*args) end
#left_outer_joins!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 788
def left_outer_joins!(*args) # :nodoc: self.left_outer_joins_values |= args self end
#limit(value)
Specifies a limit for the number of records to retrieve.
User.limit(10) # generated SQL has 'LIMIT 10'
User.limit(10).limit(20) # generated SQL has 'LIMIT 20'
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1110
def limit(value) spawn.limit!(value) end
#limit!(value)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1114
def limit!(value) # :nodoc: self.limit_value = value self end
#lock(locks = true)
Specifies locking settings (default to true
). For more information on locking, please see Locking
.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1137
def lock(locks = true) spawn.lock!(locks) end
#lock!(locks = true)
#lookup_table_klass_from_join_dependencies(table_name) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1549
def lookup_table_klass_from_join_dependencies(table_name) each_join_dependencies do |join| return join.base_klass if table_name == join.table_name end nil end
#none
Returns a chainable relation with zero records.
The returned relation implements the Null Object pattern. It is an object with defined null behavior and always returns an empty array of records without querying the database.
Any subsequent condition chained to the returned relation will continue generating an empty relation and will not fire any query to the database.
Used in cases where a method or scope could return zero records but the result needs to be chainable.
For example:
@posts = current_user.visible_posts.where(name: params[:name])
# the visible_posts method is expected to return a chainable Relation
def visible_posts
case role
when 'Country Manager'
Post.where(country: country)
when 'Reviewer'
Post.published
when 'Bad User'
Post.none # It can't be chained if [] is returned.
end
end
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1180
def none spawn.none! end
#none!
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1184
def none! # :nodoc: unless @none where!("1=0") @none = true end self end
#offset(value)
Specifies the number of rows to skip before returning rows.
User.offset(10) # generated SQL has "OFFSET 10"
Should be used with order.
User.offset(10).order("name ASC")
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1126
def offset(value) spawn.offset!(value) end
#offset!(value)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1130
def offset!(value) # :nodoc: self.offset_value = value self end
#optimizer_hints(*args)
Specify optimizer hints to be used in the SELECT statement.
Example (for MySQL):
Topic.optimizer_hints("MAX_EXECUTION_TIME(50000)", "NO_INDEX_MERGE(topics)")
# SELECT /*+ MAX_EXECUTION_TIME(50000) NO_INDEX_MERGE(topics) */ `topics`.* FROM `topics`
Example (for PostgreSQL with pg_hint_plan):
Topic.optimizer_hints("SeqScan(topics)", "Parallel(topics 8)")
# SELECT /*+ SeqScan(topics) Parallel(topics 8) */ "topics".* FROM "topics"
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1384
def optimizer_hints(*args) check_if_method_has_arguments!(__callee__, args) spawn.optimizer_hints!(*args) end
#optimizer_hints!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1389
def optimizer_hints!(*args) # :nodoc: self.optimizer_hints_values |= args self end
#or(other)
Returns a new relation, which is the logical union of this relation and the one passed as an argument.
The two relations must be structurally compatible: they must be scoping the same model, and they must differ only by #where (if no #group has been defined) or #having (if a #group is present).
Post.where("id = 1").or(Post.where("author_id = 3"))
# SELECT `posts`.* FROM `posts` WHERE ((id = 1) OR (author_id = 3))
#or!(other)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1078
def or!(other) # :nodoc: incompatible_values = structurally_incompatible_values_for(other) unless incompatible_values.empty? raise ArgumentError, "Relation passed to #or must be structurally compatible. Incompatible values: #{incompatible_values}" end self.where_clause = self.where_clause.or(other.where_clause) self.having_clause = having_clause.or(other.having_clause) self.references_values |= other.references_values self end
#order(*args)
Applies an ORDER BY
clause to a query.
#order
accepts arguments in one of several formats.
symbols
The symbol represents the name of the column you want to order the results by.
User.order(:name)
# SELECT "users".* FROM "users" ORDER BY "users"."name" ASC
By default, the order is ascending. If you want descending order, you can map the column name symbol to :desc
.
User.order(email: :desc)
# SELECT "users".* FROM "users" ORDER BY "users"."email" DESC
Multiple columns can be passed this way, and they will be applied in the order specified.
User.order(:name, email: :desc)
# SELECT "users".* FROM "users" ORDER BY "users"."name" ASC, "users"."email" DESC
strings
Strings are passed directly to the database, allowing you to specify simple SQL expressions.
This could be a source of SQL injection, so only strings composed of plain column names and simple function(column_name)
expressions with optional ASC
/DESC
modifiers are allowed.
User.order('name')
# SELECT "users".* FROM "users" ORDER BY name
User.order('name DESC')
# SELECT "users".* FROM "users" ORDER BY name DESC
User.order('name DESC, email')
# SELECT "users".* FROM "users" ORDER BY name DESC, email
Arel
If you need to pass in complicated expressions that you have verified are safe for the database, you can use ::Arel
.
User.order(Arel.sql('end_date - start_date'))
# SELECT "users".* FROM "users" ORDER BY end_date - start_date
Custom query syntax, like JSON columns for PostgreSQL, is supported in this way.
User.order(Arel.sql("payload->>'kind'"))
# SELECT "users".* FROM "users" ORDER BY payload->>'kind'
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 595
def order(*args) check_if_method_has_arguments!(__callee__, args) do sanitize_order_arguments(args) end spawn.order!(*args) end
#order!(*args)
Same as #order but operates on relation in-place instead of copying.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 603
def order!(*args) # :nodoc: preprocess_order_args(args) unless args.empty? self.order_values |= args self end
#order_column(field) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1926
def order_column(field) arel_column(field) do |attr_name| if attr_name == "count" && !group_values.empty? table[attr_name] else Arel.sql(connection.quote_table_name(attr_name)) end end end
#preload(*args)
Specify associations args
to be eager loaded using separate queries. A separate query is performed for each association.
users = User.preload(:address).limit(5)
users.each do |user|
user.address.city
end
# SELECT "users".* FROM "users" LIMIT 5
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
Instead of loading the 5 addresses with 5 separate queries, all addresses are loaded with a separate query.
Loading multiple and nested associations is possible using Hashes and Arrays, similar to #includes:
User.preload(:address, friends: [:address, :followers])
# SELECT "users".* FROM "users"
# SELECT "addresses".* FROM "addresses" WHERE "addresses"."id" IN (1,2,3,4,5)
# SELECT "friends".* FROM "friends" WHERE "friends"."user_id" IN (1,2,3,4,5)
# SELECT ...
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 299
def preload(*args) check_if_method_has_arguments!(__callee__, args) spawn.preload!(*args) end
#preload!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 304
def preload!(*args) # :nodoc: self.preload_values |= args self end
#preprocess_order_args(order_args) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1874
def preprocess_order_args(order_args) @klass.disallow_raw_sql!( order_args.flat_map { |a| a.is_a?(Hash) ? a.keys : a }, permit: connection.column_name_with_order_matcher ) validate_order_args(order_args) references = column_references(order_args) self.references_values |= references unless references.empty? # if a symbol is given we prepend the quoted table name order_args.map! do |arg| case arg when Symbol order_column(arg.to_s).asc when Hash arg.map { |field, dir| case field when Arel::Nodes::SqlLiteral, Arel::Nodes::Node, Arel::Attribute field.public_send(dir.downcase) else order_column(field.to_s).public_send(dir.downcase) end } else arg end end.flatten! end
#process_select_args(fields) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1996
def process_select_args(fields) fields.flat_map do |field| if field.is_a?(Hash) transform_select_hash_values(field) else field end end end
#readonly(value = true)
Mark a relation as readonly. Attempting to update a record will result in an error.
users = User.readonly
users.first.save
#=> ActiveRecord::ReadOnlyRecord: User is marked as readonly
To make a readonly relation writable, pass false
.
users.readonly(false)
users.first.save
#=> true
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1208
def readonly(value = true) spawn.readonly!(value) end
#readonly!(value = true)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1212
def readonly!(value = true) # :nodoc: self.readonly_value = value self end
#references(*table_names)
Use to indicate that the given table_names
are referenced by an SQL string, and should therefore be JOIN
ed in any query rather than loaded separately. This method only works in conjunction with #includes. See #includes for more details.
User.includes(:posts).where("posts.name = 'foo'")
# Doesn't JOIN the posts table, resulting in an error.
User.includes(:posts).where("posts.name = 'foo'").references(:posts)
# Query now knows the string references posts, so adds a JOIN
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 332
def references(*table_names) check_if_method_has_arguments!(__callee__, table_names) spawn.references!(*table_names) end
#references!(*table_names)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 337
def references!(*table_names) # :nodoc: self.references_values |= table_names self end
#regroup(*args)
Allows you to change a previously set group statement.
Post.group(:title, :body)
# SELECT `posts`.`*` FROM `posts` GROUP BY `posts`.`title`, `posts`.`body`
Post.group(:title, :body).regroup(:title)
# SELECT `posts`.`*` FROM `posts` GROUP BY `posts`.`title`
This is short-hand for unscope(:group).group(fields)
. Note that we’re unscoping the entire group statement.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 532
def regroup(*args) check_if_method_has_arguments!(__callee__, args) spawn.regroup!(*args) end
#regroup!(*args)
Same as #regroup but operates on relation in-place instead of copying.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 538
def regroup!(*args) # :nodoc: self.group_values = args self end
#reorder(*args)
Replaces any existing order defined on the relation with the specified order.
User.order('email DESC').reorder('id ASC') # generated SQL has 'ORDER BY id ASC'
Subsequent calls to order on the same relation will be appended. For example:
User.order('email DESC').reorder('id ASC').order('name ASC')
generates a query with ORDER BY id ASC, name ASC
.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 651
def reorder(*args) check_if_method_has_arguments!(__callee__, args) do sanitize_order_arguments(args) end spawn.reorder!(*args) end
#reorder!(*args)
Same as #reorder but operates on relation in-place instead of copying.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 659
def reorder!(*args) # :nodoc: preprocess_order_args(args) args.uniq! self.reordering_value = true self.order_values = args self end
#reselect(*args)
Allows you to change a previously set select statement.
Post.select(:title, :body)
# SELECT `posts`.`title`, `posts`.`body` FROM `posts`
Post.select(:title, :body).reselect(:created_at)
# SELECT `posts`.`created_at` FROM `posts`
This is short-hand for unscope(:select).select(fields)
. Note that we’re unscoping the entire select statement.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 480
def reselect(*args) check_if_method_has_arguments!(__callee__, args) args = process_select_args(args) spawn.reselect!(*args) end
#reselect!(*args)
Same as #reselect but operates on relation in-place instead of copying.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 487
def reselect!(*args) # :nodoc: self.select_values = args self end
#resolve_arel_attributes(attrs) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1945
def resolve_arel_attributes(attrs) attrs.flat_map do |attr| case attr when Arel::Predications attr when Hash attr.flat_map do |table, columns| table = table.to_s Array(columns).map do |column| predicate_builder.resolve_arel_attribute(table, column) end end else attr = attr.to_s if attr.include?(".") table, column = attr.split(".", 2) predicate_builder.resolve_arel_attribute(table, column) else attr end end end end
#reverse_order
Reverse the existing order clause on the relation.
User.order('name ASC').reverse_order # generated SQL has 'ORDER BY name DESC'
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1397
def reverse_order spawn.reverse_order! end
#reverse_order!
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1401
def reverse_order! # :nodoc: orders = order_values.compact_blank self.order_values = reverse_sql_order(orders) self end
#reverse_sql_order(order_query) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1814
def reverse_sql_order(order_query) if order_query.empty? return [table[primary_key].desc] if primary_key raise IrreversibleOrderError, "Relation has no current order and table has no primary key to be used as default order" end order_query.flat_map do |o| case o when Arel::Attribute o.desc when Arel::Nodes::Ordering o.reverse when Arel::Nodes::NodeExpression o.desc when String if does_not_support_reverse?(o) raise IrreversibleOrderError, "Order #{o.inspect} cannot be reversed automatically" end o.split(",").map! do |s| s.strip! s.gsub!(/\sasc\Z/i, " DESC") || s.gsub!(/\sdesc\Z/i, " ASC") || (s << " DESC") end else o end end end
#rewhere(conditions)
Allows you to change a previously set where condition for a given attribute, instead of appending to that condition.
Post.where(trashed: true).where(trashed: false)
# WHERE `trashed` = 1 AND `trashed` = 0
Post.where(trashed: true).rewhere(trashed: false)
# WHERE `trashed` = 0
Post.where(active: true).where(trashed: true).rewhere(trashed: false)
# WHERE `active` = 1 AND `trashed` = 0
This is short-hand for unscope(where: conditions.keys).where(conditions)
. Note that unlike reorder, we’re only unscoping the named conditions – not the entire where statement.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 960
def rewhere(conditions) return unscope(:where) if conditions.nil? scope = spawn where_clause = scope.build_where_clause(conditions) scope.unscope!(where: where_clause.extract_attributes) scope.where_clause += where_clause scope end
#sanitize_order_arguments(order_args) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1905
def sanitize_order_arguments(order_args) order_args.map! do |arg| klass.sanitize_sql_for_order(arg) end end
#select(*fields)
Works in two unique ways.
First: takes a block so it can be used just like Array#select
.
Model.all.select { |m| m.field == value }
This will build an array of objects from the database for the scope, converting them into an array and iterating through them using Array#select
.
Second: Modifies the SELECT statement for the query so that only certain fields are retrieved:
Model.select(:field)
# => [#<Model id: nil, field: "value">]
Although in the above example it looks as though this method returns an array, it actually returns a relation object and can have other query methods appended to it, such as the other methods in QueryMethods
.
The argument to the method can also be an array of fields.
Model.select(:field, :other_field, :and_one_more)
# => [#<Model id: nil, field: "value", other_field: "value", and_one_more: "value">]
The argument also can be a hash of fields and aliases.
Model.select(models: { field: :alias, other_field: :other_alias })
# => [#<Model id: nil, alias: "value", other_alias: "value">]
Model.select(models: [:field, :other_field])
# => [#<Model id: nil, field: "value", other_field: "value">]
You can also use one or more strings, which will be used unchanged as SELECT fields.
Model.select('field AS field_one', 'other_field AS field_two')
# => [#<Model id: nil, field_one: "value", field_two: "value">]
If an alias was specified, it will be accessible from the resulting objects:
Model.select('field AS field_one').first.field_one
# => "value"
Accessing attributes of an object that do not have fields retrieved by a select except id
will throw ::ActiveModel::MissingAttributeError
:
Model.select(:field).first.other_field
# => ActiveModel::MissingAttributeError: missing attribute 'other_field' for Model
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 390
def select(*fields) if block_given? if fields.any? raise ArgumentError, "`select' with block doesn't take arguments." end return super() end check_if_method_has_arguments!(__callee__, fields, "Call `select' with at least one field.") fields = process_select_args(fields) spawn._select!(*fields) end
#select_association_list(associations, stashed_joins = nil) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1638
def select_association_list(associations, stashed_joins = nil) result = [] associations.each do |association| case association when Hash, Symbol, Array result << association when ActiveRecord::Associations::JoinDependency stashed_joins&.<< association else yield association if block_given? end end result end
#select_named_joins(join_names, stashed_joins = nil, &block) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1626
def select_named_joins(join_names, stashed_joins = nil, &block) cte_joins, associations = join_names.partition do |join_name| Symbol === join_name && with_values.any? { _1.key?(join_name) } end cte_joins.each do |cte_name| block&.call(CTEJoin.new(cte_name)) end select_association_list(associations, stashed_joins, &block) end
#skip_preloading!
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1412
def skip_preloading! # :nodoc: self.skip_preloading_value = true self end
#skip_query_cache!(value = true)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1407
def skip_query_cache!(value = true) # :nodoc: self.skip_query_cache_value = value self end
#strict_loading(value = true)
Sets the returned relation to strict_loading mode. This will raise an error if the record tries to lazily load an association.
user = User.strict_loading.first
user.comments.to_a
#=> ActiveRecord::StrictLoadingViolationError
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1223
def strict_loading(value = true) spawn.strict_loading!(value) end
#strict_loading!(value = true)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1227
def strict_loading!(value = true) # :nodoc: self.strict_loading_value = value self end
#structurally_compatible?(other) ⇒ Boolean
Checks whether the given relation is structurally compatible with this relation, to determine if it’s possible to use the #and and #or methods without raising an error. Structurally compatible is defined as: they must be scoping the same model, and they must differ only by #where (if no #group has been defined) or #having (if a #group is present).
Post.where("id = 1").structurally_compatible?(Post.where("author_id = 3"))
# => true
Post.joins(:comments).structurally_compatible?(Post.where("id = 1"))
# => false
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1020
def structurally_compatible?(other) structurally_incompatible_values_for(other).empty? end
#structurally_incompatible_values_for(other) (private)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 2036
def structurally_incompatible_values_for(other) values = other.values STRUCTURAL_VALUE_METHODS.reject do |method| v1, v2 = @values[method], values[method] if v1.is_a?(Array) next true unless v2.is_a?(Array) v1 = v1.uniq v2 = v2.uniq end v1 == v2 end end
#table_name_matches?(from) ⇒ Boolean
(private)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1808
def table_name_matches?(from) table_name = Regexp.escape(table.name) quoted_table_name = Regexp.escape(connection.quote_table_name(table.name)) /(?:\A|(?<!FROM)\s)(?:\b#{table_name}\b|#{quoted_table_name})(?!\.)/i.match?(from.to_s) end
#transform_select_hash_values(fields) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 2006
def transform_select_hash_values(fields) fields.flat_map do |key, columns_aliases| case columns_aliases when Hash columns_aliases.map do |column, column_alias| if values[:joins]&.include?(key) references = PredicateBuilder.references({ key.to_s => fields[key] }) self.references_values |= references unless references.empty? end arel_column("#{key}.#{column}") do predicate_builder.resolve_arel_attribute(key.to_s, column) end.as(column_alias.to_s) end when Array columns_aliases.map do |column| arel_column("#{key}.#{column}", &:itself) end when String, Symbol arel_column(key.to_s) do predicate_builder.resolve_arel_attribute(klass.table_name, key.to_s) end.as(columns_aliases.to_s) end end end
#uniq!(name)
Deduplicate multiple values.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1440
def uniq!(name) if values = @values[name] values.uniq! if values.is_a?(Array) && !values.empty? end self end
#unscope(*args)
Removes an unwanted relation that is already defined on a chain of relations. This is useful when passing around chains of relations and would like to modify the relations without reconstructing the entire chain.
User.order('email DESC').unscope(:order) == User.all
The method arguments are symbols which correspond to the names of the methods which should be unscoped. The valid arguments are given in VALID_UNSCOPING_VALUES. The method can also be called with multiple arguments. For example:
User.order('email DESC').select('id').where(name: "John")
.unscope(:order, :select, :where) == User.all
One can additionally pass a hash as an argument to unscope specific :where
values. This is done by passing a hash with a single key-value pair. The key should be :where
and the value should be the where value to unscope. For example:
User.where(name: "John", active: true).unscope(where: :name)
== User.where(active: true)
This method is similar to #except
, but unlike #except
, it persists across merges:
User.order('email').merge(User.except(:order))
== User.order('email')
User.order('email').merge(User.unscope(:order))
== User.all
This means it can be used in association definitions:
has_many :comments, -> { unscope(where: :trashed) }
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 705
def unscope(*args) check_if_method_has_arguments!(__callee__, args) spawn.unscope!(*args) end
#unscope!(*args)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 710
def unscope!(*args) # :nodoc: self.unscope_values += args args.each do |scope| case scope when Symbol scope = :left_outer_joins if scope == :left_joins if !VALID_UNSCOPING_VALUES.include?(scope) raise ArgumentError, "Called unscope() with invalid unscoping argument ':#{scope}'. Valid arguments are :#{VALID_UNSCOPING_VALUES.to_a.join(", :")}." end assert_mutability! @values.delete(scope) when Hash scope.each do |key, target_value| if key != :where raise ArgumentError, "Hash arguments in .unscope(*args) must have :where as the key." end target_values = resolve_arel_attributes(Array.wrap(target_value)) self.where_clause = where_clause.except(*target_values) end else raise ArgumentError, "Unrecognized scoping: #{args.inspect}. Use .unscope(where: :attribute_name) or .unscope(:order), for example." end end self end
#validate_order_args(args) (private)
[ GitHub ]# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1862
def validate_order_args(args) args.each do |arg| next unless arg.is_a?(Hash) arg.each do |_key, value| unless VALID_DIRECTIONS.include?(value) raise ArgumentError, "Direction \"#{value}\" is invalid. Valid directions are: #{VALID_DIRECTIONS.to_a.inspect}" end end end end
#where(*args)
Returns a new relation, which is the result of filtering the current relation according to the conditions in the arguments.
#where
accepts conditions in one of several formats. In the examples below, the resulting SQL is given as an illustration; the actual query generated may be different depending on the database adapter.
String
A single string, without additional arguments, is passed to the query constructor as an SQL fragment, and used in the where clause of the query.
Client.where("orders_count = '2'")
# SELECT * from clients where orders_count = '2';
Note that building your own string from user input may expose your application to injection attacks if not done properly. As an alternative, it is recommended to use one of the following methods.
Array
If an array is passed, then the first element of the array is treated as a template, and the remaining elements are inserted into the template to generate the condition. Active Record takes care of building the query to avoid injection attacks, and will convert from the ruby type to the database type where needed. Elements are inserted into the string in the order in which they appear.
User.where(["name = ? and email = ?", "Joe", "joe@example.com"])
# SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
Alternatively, you can use named placeholders in the template, and pass a hash as the second element of the array. The names in the template are replaced with the corresponding values from the hash.
User.where(["name = :name and email = :email", { name: "Joe", email: "joe@example.com" }])
# SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
This can make for more readable code in complex queries.
Lastly, you can use sprintf-style % escapes in the template. This works slightly differently than the previous methods; you are responsible for ensuring that the values in the template are properly quoted. The values are passed to the connector for quoting, but the caller is responsible for ensuring they are enclosed in quotes in the resulting SQL. After quoting, the values are inserted using the same escapes as the Ruby core method Kernel.sprintf
.
User.where(["name = '%s' and email = '%s'", "Joe", "joe@example.com"])
# SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
If #where
is called with multiple arguments, these are treated as if they were passed as the elements of a single array.
User.where("name = :name and email = :email", { name: "Joe", email: "joe@example.com" })
# SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com';
When using strings to specify conditions, you can use any operator available from the database. While this provides the most flexibility, you can also unintentionally introduce dependencies on the underlying database. If your code is intended for general consumption, test with multiple database backends.
Hash
#where
will also accept a hash condition, in which the keys are fields and the values are values to be searched for.
Fields can be symbols or strings. Values can be single values, arrays, or ranges.
User.where(name: "Joe", email: "joe@example.com")
# SELECT * FROM users WHERE name = 'Joe' AND email = 'joe@example.com'
User.where(name: ["Alice", "Bob"])
# SELECT * FROM users WHERE name IN ('Alice', 'Bob')
User.where(created_at: (Time.now.midnight - 1.day)..Time.now.midnight)
# SELECT * FROM users WHERE (created_at BETWEEN '2012-06-09 07:00:00.000000' AND '2012-06-10 07:00:00.000000')
In the case of a belongs_to relationship, an association key can be used to specify the model if an ::ActiveRecord
object is used as the value.
= Author.find(1)
# The following queries will be equivalent:
Post.where(author: )
Post.where(author_id: )
This also works with polymorphic belongs_to relationships:
treasure = Treasure.create(name: 'gold coins')
treasure.price_estimates << PriceEstimate.create(price: 125)
# The following queries will be equivalent:
PriceEstimate.where(estimate_of: treasure)
PriceEstimate.where(estimate_of_type: 'Treasure', estimate_of_id: treasure)
::Hash
conditions may also be specified in a tuple-like syntax. ::Hash
keys may be an array of columns with an array of tuples as values.
Article.where([:, :id] => [[15, 1], [15, 2]])
# SELECT * FROM articles WHERE author_id = 15 AND id = 1 OR author_id = 15 AND id = 2
Joins
If the relation is the result of a join, you may create a condition which uses any of the tables in the join. For string and array conditions, use the table name in the condition.
User.joins(:posts).where("posts.created_at < ?", Time.now)
For hash conditions, you can either use the table name in the key, or use a sub-hash.
User.joins(:posts).where("posts.published" => true)
User.joins(:posts).where(posts: { published: true })
No Argument
If no argument is passed, #where
returns a new instance of QueryMethods::WhereChain
, that can be chained with WhereChain#not, WhereChain#missing, or WhereChain#associated.
Chaining with WhereChain#not:
User.where.not(name: "Jon")
# SELECT * FROM users WHERE name != 'Jon'
Chaining with WhereChain#associated:
Post.where.associated(: )
# SELECT "posts".* FROM "posts"
# INNER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# WHERE "authors"."id" IS NOT NULL
Chaining with WhereChain#missing:
Post.where.missing(: )
# SELECT "posts".* FROM "posts"
# LEFT OUTER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# WHERE "authors"."id" IS NULL
Blank Condition
If the condition is any blank-ish object, then #where
is a no-op and returns the current relation.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 932
def where(*args) if args.empty? WhereChain.new(spawn) elsif args.length == 1 && args.first.blank? self else spawn.where!(*args) end end
#where!(opts, *rest)
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 942
def where!(opts, *rest) # :nodoc: self.where_clause += build_where_clause(opts, rest) self end
#with(*args)
Add a Common Table Expression (CTE) that you can then reference within another SELECT statement.
Note: CTE’s are only supported in MySQL for versions 8.0 and above. You will not be able to use CTE’s with MySQL 5.7.
Post.with(posts_with_tags: Post.where("tags_count > ?", 0))
# => ActiveRecord::Relation
# WITH posts_with_tags AS (
# SELECT * FROM posts WHERE (tags_count > 0)
# )
# SELECT * FROM posts
Once you define Common Table Expression you can use custom FROM
value or JOIN
to reference it.
Post.with(posts_with_tags: Post.where("tags_count > ?", 0)).from("posts_with_tags AS posts")
# => ActiveRecord::Relation
# WITH posts_with_tags AS (
# SELECT * FROM posts WHERE (tags_count > 0)
# )
# SELECT * FROM posts_with_tags AS posts
Post.with(posts_with_tags: Post.where("tags_count > ?", 0)).joins("JOIN posts_with_tags ON posts_with_tags.id = posts.id")
# => ActiveRecord::Relation
# WITH posts_with_tags AS (
# SELECT * FROM posts WHERE (tags_count > 0)
# )
# SELECT * FROM posts JOIN posts_with_tags ON posts_with_tags.id = posts.id
It is recommended to pass a query as Relation
. If that is not possible and you have verified it is safe for the database, you can pass it as SQL literal using ::Arel
.
Post.with(popular_posts: Arel.sql("... complex sql to calculate posts popularity ..."))
Great caution should be taken to avoid SQL injection vulnerabilities. This method should not be used with unsafe values that include unsanitized input.
To add multiple CTEs just pass multiple key-value pairs
Post.with(
posts_with_comments: Post.where("comments_count > ?", 0),
posts_with_tags: Post.where("tags_count > ?", 0)
)
or chain multiple #with
calls
Post
.with(posts_with_comments: Post.where("comments_count > ?", 0))
.with(posts_with_tags: Post.where("tags_count > ?", 0))
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 459
def with(*args) check_if_method_has_arguments!(__callee__, args) spawn.with!(*args) end
#with!(*args)
Like #with, but modifies relation in place.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 465
def with!(*args) # :nodoc: self.with_values += args self end
#without(*records)
Alias for #excluding.
# File 'activerecord/lib/active_record/relation/query_methods.rb', line 1480
alias :without :excluding