Active Record Relation
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| JoinOperation | = | Struct.new(:relation, :join_class, :on) |
| ASSOCIATION_METHODS | = | [:includes, :eager_load, :preload] |
| MULTI_VALUE_METHODS | = | [:select, :group, :order, :joins, :where, :having, :bind] |
| SINGLE_VALUE_METHODS | = | [:limit, :offset, :lock, :readonly, :from, :reordering, :reverse_order, :uniq] |
| [RW] | default_scoped | |
| [RW] | default_scoped? | |
| [RW] | extensions | |
| [R] | klass | |
| [R] | loaded | |
| [R] | loaded? | |
| [R] | table |
# File activerecord/lib/active_record/relation.rb, line 18 def initialize(klass, table) @klass, @table = klass, table @implicit_readonly = nil @loaded = false @default_scoped = false SINGLE_VALUE_METHODS.each {|v| instance_variable_set(:"@#{v}_value", nil)} (ASSOCIATION_METHODS + MULTI_VALUE_METHODS).each {|v| instance_variable_set(:"@#{v}_values", [])} @extensions = [] @create_with_value = {} end
Deletes the row with a primary key matching the id argument,
using a SQL DELETE statement, and returns the number of rows
deleted. Active Record objects are not instantiated, so the object's
callbacks are not executed, including any :dependent
association options or Observer methods.
You can delete multiple rows at once by passing an Array of ids.
Note: Although it is often much faster than the alternative,
#destroy, skipping callbacks might bypass business logic in
your application that ensures referential integrity or performs other
essential jobs.
Examples
# Delete a single row Todo.delete(1) # Delete multiple rows Todo.delete([2,3,4])
Deletes the records matching conditions without instantiating
the records first, and hence not calling the destroy method
nor invoking callbacks. This is a single SQL DELETE statement that goes
straight to the database, much more efficient than
destroy_all. Be careful with relations though, in particular
:dependent rules defined on associations are not honored.
Returns the number of rows affected.
Parameters
-
conditions- Conditions are specified the same way as withfindmethod.
Example
Post.delete_all("person_id = 5 AND (category = 'Something' OR category = 'Else')") Post.delete_all(["person_id = ? AND (category = ? OR category = ?)", 5, 'Something', 'Else']) Post.where(:person_id => 5).where(:category => ['Something', 'Else']).delete_all
Both calls delete the affected posts all at once with a single DELETE
statement. If you need to destroy dependent associations or call your
before_* or after_destroy callbacks, use the
destroy_all method instead.
# File activerecord/lib/active_record/relation.rb, line 404 def delete_all(conditions = nil) raise ActiveRecordError.new("delete_all doesn't support limit scope") if self.limit_value IdentityMap.repository[symbolized_base_class] = {} if IdentityMap.enabled? if conditions where(conditions).delete_all else statement = arel.compile_delete affected = @klass.connection.delete(statement, 'SQL', bind_values) reset affected end end
Destroy an object (or multiple objects) that has the given id, the object is instantiated first, therefore all callbacks and filters are fired off before the object is deleted. This method is less efficient than ActiveRecord#delete but allows cleanup methods and other actions to be run.
This essentially finds the object (or multiple objects) with the given id, creates a new object from the attributes, and then calls destroy on it.
Parameters
Examples
# Destroy a single object Todo.destroy(1) # Destroy multiple objects todos = [1,2,3] Todo.destroy(todos)
Destroys the records matching conditions by instantiating each
record and calling its destroy method. Each object's
callbacks are executed (including :dependent association
options and before_destroy/after_destroy Observer methods). Returns the collection of
objects that were destroyed; each will be frozen, to reflect that no
changes should be made (since they can't be persisted).
Note: Instantiation, callback execution, and deletion of each record can be
time consuming when you're removing many records at once. It generates
at least one SQL DELETE query per record (or possibly more, to
enforce your callbacks). If you want to delete many rows quickly, without
concern for their associations or callbacks, use delete_all
instead.
Parameters
-
conditions- A string, array, or hash that specifies which records to destroy. If omitted, all records are destroyed. See the Conditions section in the introduction to ActiveRecord::Base for more information.
Examples
Person.destroy_all("last_login < '2004-04-04'") Person.destroy_all(:status => "inactive") Person.where(:age => 0..18).destroy_all
Returns true if there are no records.
Runs EXPLAIN on the query or queries triggered by this relation and returns the result as a string. The string is formatted imitating the ones printed by the database shell.
Note that this method actually runs the queries, since the results of some are needed by the next ones when eager loading is going on.
Please see further details in the Active Record Query Interface guide.
Tries to load the first record; if it fails, then create is
called with the same arguments as this method.
Expects arguments in the same format as Base.create.
Examples
# Find the first user named Penélope or create a new one. User.where(:first_name => 'Penélope').first_or_create # => <User id: 1, first_name: 'Penélope', last_name: nil> # Find the first user named Penélope or create a new one. # We already have one so the existing record will be returned. User.where(:first_name => 'Penélope').first_or_create # => <User id: 1, first_name: 'Penélope', last_name: nil> # Find the first user named Scarlett or create a new one with a particular last name. User.where(:first_name => 'Scarlett').first_or_create(:last_name => 'Johansson') # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'> # Find the first user named Scarlett or create a new one with a different last name. # We already have one so the existing record will be returned. User.where(:first_name => 'Scarlett').first_or_create do |user| user.last_name = "O'Hara" end # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
Like first_or_create but calls create! so an
exception is raised if the created record is invalid.
Expects arguments in the same format as Base.create!.
Like first_or_create but calls new instead of
create.
Expects arguments in the same format as Base.new.
# File activerecord/lib/active_record/relation.rb, line 31 def insert(values) primary_key_value = nil if primary_key && Hash === values primary_key_value = values[values.keys.find { |k| k.name == primary_key }] if !primary_key_value && connection.prefetch_primary_key?(klass.table_name) primary_key_value = connection.next_sequence_value(klass.sequence_name) values[klass.arel_table[klass.primary_key]] = primary_key_value end end im = arel.create_insert im.into @table conn = @klass.connection substitutes = values.sort_by { |arel_attr,_| arel_attr.name } binds = substitutes.map do |arel_attr, value| [@klass.columns_hash[arel_attr.name], value] end substitutes.each_with_index do |tuple, i| tuple[1] = conn.substitute_at(binds[i][0], i) end if values.empty? # empty insert im.values = Arel.sql(connection.empty_insert_statement_value) else im.insert substitutes end conn.insert( im, 'SQL', primary_key, primary_key_value, nil, binds) end
Joins that are also marked for preloading. In which case we should just eager load them. Note that this is a naive implementation because we could have strings and symbols which represent the same association, but that aren't matched by this. Also, we could have nested hashes which partially match, e.g. { :a => :b } & { :a => [:b, :c] }
Scope all queries to the current scope.
Example
Comment.where(:post_id => 1).scoping do Comment.first # SELECT * FROM comments WHERE post_id = 1 end
Please check unscoped if you want to remove all previous scopes (including the default_scope) during the execution of a block.
Returns size of the records.
# File activerecord/lib/active_record/relation.rb, line 149 def to_a # We monitor here the entire execution rather than individual SELECTs # because from the point of view of the user fetching the records of a # relation is a single unit of work. You want to know if this call takes # too long, not if the individual queries take too long. # # It could be the case that none of the queries involved surpass the # threshold, and at the same time the sum of them all does. The user # should get a query plan logged in that case. logging_query_plan do exec_queries end end
Updates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.
Parameters
-
id- This should be the id or an array of ids to be updated. -
attributes- This should be a hash of attributes or an array of hashes.
Examples
# Updates one record Person.update(15, :user_name => 'Samuel', :group => 'expert') # Updates multiple records people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } } Person.update(people.keys, people.values)
Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied. This method constructs a single SQL UPDATE statement and sends it straight to the database. It does not instantiate the involved models and it does not trigger Active Record callbacks or validations.
Parameters
-
updates- A string, array, or hash representing the SET part of an SQL statement. -
conditions- A string, array, or hash representing the WHERE part of an SQL statement. See conditions in the intro. -
options- Additional options are:limitand:order, see the examples for usage.
Examples
# Update all customers with the given attributes Customer.update_all :wants_email => true # Update all books with 'Rails' in their title Book.update_all "author = 'David'", "title LIKE '%Rails%'" # Update all avatars migrated more than a week ago Avatar.update_all ['migrated_at = ?', Time.now.utc], ['migrated_at > ?', 1.week.ago] # Update all books that match conditions, but limit it to 5 ordered by date Book.update_all "author = 'David'", "title LIKE '%Rails%'", :order => 'created_at', :limit => 5 # Conditions from the current relation also works Book.where('title LIKE ?', '%Rails%').update_all(:author => 'David') # The same idea applies to limit and order Book.where('title LIKE ?', '%Rails%').order(:created_at).limit(5).update_all(:author => 'David')
# File activerecord/lib/active_record/relation.rb, line 274 def update_all(updates, conditions = nil, options = {}) IdentityMap.repository[symbolized_base_class].clear if IdentityMap.enabled? if conditions || options.present? where(conditions).apply_finder_options(options.slice(:limit, :order)).update_all(updates) else stmt = Arel::UpdateManager.new(arel.engine) stmt.set Arel.sql(@klass.send(:sanitize_sql_for_assignment, updates)) stmt.table(table) stmt.key = table[primary_key] if joins_values.any? @klass.connection.join_to_update(stmt, arel) else stmt.take(arel.limit) stmt.order(*arel.orders) stmt.wheres = arel.constraints end @klass.connection.update stmt, 'SQL', bind_values end end
# File activerecord/lib/active_record/relation.rb, line 461 def where_values_hash equalities = with_default_scope.where_values.grep(Arel::Nodes::Equality).find_all { |node| node.left.relation.name == table_name } Hash[equalities.map { |where| [where.left.name, where.right] }].with_indifferent_access end