Module: ActiveRecord::ModelSchema::ClassMethods

Defined in:
activerecord/lib/active_record/model_schema.rb

Instance Method Summary collapse

Instance Method Details

#_default_attributes ⇒ Object

:nodoc:



496
497
498
499
 
# File 'activerecord/lib/active_record/model_schema.rb', line 496

def _default_attributes # :nodoc:
  load_schema
  @default_attributes ||= ActiveModel::AttributeSet.new({})
end

#_returning_columns_for_insert ⇒ Object

:nodoc:



432
433
434
435
436
 
# File 'activerecord/lib/active_record/model_schema.rb', line 432

def _returning_columns_for_insert # :nodoc:
  @_returning_columns_for_insert ||= columns.filter_map do |c|
    c.name if connection.return_value_after_insert?(c)
  end
end

#attribute_types ⇒ Object

:nodoc:



438
439
440
441
 
# File 'activerecord/lib/active_record/model_schema.rb', line 438

def attribute_types # :nodoc:
  load_schema
  @attribute_types ||= Hash.new(Type.default_value)
end

#attributes_builder ⇒ Object

:nodoc:



414
415
416
417
418
419
420
 
# File 'activerecord/lib/active_record/model_schema.rb', line 414

def attributes_builder # :nodoc:
  unless defined?(@attributes_builder) && @attributes_builder
    defaults = _default_attributes.except(*(column_names - [primary_key]))
    @attributes_builder = ActiveModel::AttributeSet::Builder.new(attribute_types, defaults)
  end
  @attributes_builder
end

#column_defaults ⇒ Object

Returns a hash where the keys are column names and the values are default values when instantiating the Active Record object for this table.



491
492
493
494
 
# File 'activerecord/lib/active_record/model_schema.rb', line 491

def column_defaults
  load_schema
  @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze
end

#column_for_attribute(name) ⇒ Object

Returns the column object for the named attribute. Returns an ActiveRecord::ConnectionAdapters::NullColumn if the named attribute does not exist.

class Person < ActiveRecord::Base
end

person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>

person.column_for_attribute(:nothing)
# => #<ActiveRecord::ConnectionAdapters::NullColumn:0xXXX @name=nil, @sql_type=nil, @cast_type=#<Type::Value>, ...>



482
483
484
485
486
487
 
# File 'activerecord/lib/active_record/model_schema.rb', line 482

def column_for_attribute(name)
  name = name.to_s
  columns_hash.fetch(name) do
    ConnectionAdapters::NullColumn.new(name)
  end
end

#column_names ⇒ Object

Returns an array of column names as strings.



502
503
504
 
# File 'activerecord/lib/active_record/model_schema.rb', line 502

def column_names
  @column_names ||= columns.map(&:name).freeze
end

#columns ⇒ Object 



427
428
429
430
 
# File 'activerecord/lib/active_record/model_schema.rb', line 427

def columns
  load_schema
  @columns ||= columns_hash.values.freeze
end

#columns_hash ⇒ Object

:nodoc:



422
423
424
425
 
# File 'activerecord/lib/active_record/model_schema.rb', line 422

def columns_hash # :nodoc:
  load_schema
  @columns_hash
end

#content_columns ⇒ Object

Returns an array of column objects where the primary id, all columns ending in “_id” or “_count”, and columns used for single table inheritance have been removed.



513
514
515
516
517
518
519
 
# File 'activerecord/lib/active_record/model_schema.rb', line 513

def content_columns
  @content_columns ||= columns.reject do |c|
    c.name == primary_key ||
    c.name == inheritance_column ||
    c.name.end_with?("_id", "_count")
  end.freeze
end

#full_table_name_prefix ⇒ Object

:nodoc:



296
297
298
 
# File 'activerecord/lib/active_record/model_schema.rb', line 296

def full_table_name_prefix # :nodoc:
  (module_parents.detect { |p| p.respond_to?(:table_name_prefix) } || self).table_name_prefix
end

#full_table_name_suffix ⇒ Object

:nodoc:



300
301
302
 
# File 'activerecord/lib/active_record/model_schema.rb', line 300

def full_table_name_suffix # :nodoc:
  (module_parents.detect { |p| p.respond_to?(:table_name_suffix) } || self).table_name_suffix
end

#ignored_columns ⇒ Object

The list of columns names the model should ignore. Ignored columns won’t have attribute accessors defined, and won’t be referenced in SQL queries.



325
326
327
 
# File 'activerecord/lib/active_record/model_schema.rb', line 325

def ignored_columns
  @ignored_columns || superclass.ignored_columns
end

#ignored_columns=(columns) ⇒ Object

Sets the columns names the model should ignore. Ignored columns won’t have attribute accessors defined, and won’t be referenced in SQL queries.

A common usage pattern for this method is to ensure all references to an attribute have been removed and deployed, before a migration to drop the column from the database has been deployed and run. Using this two step approach to dropping columns ensures there is no code that raises errors due to having a cached schema in memory at the time the schema migration is run.

For example, given a model where you want to drop the “category” attribute, first mark it as ignored:

class Project < ActiveRecord::Base
  # schema:
  #   id         :bigint
  #   name       :string, limit: 255
  #   category   :string, limit: 255

  self.ignored_columns += [:category]
end

The schema still contains “category”, but now the model omits it, so any meta-driven code or schema caching will not attempt to use the column:

Project.columns_hash["category"] => nil

You will get an error if accessing that attribute directly, so ensure all usages of the column are removed (automated tests can help you find any usages).

user = Project.create!(name: "First Project")
user.category # => raises NoMethodError



360
361
362
363
 
# File 'activerecord/lib/active_record/model_schema.rb', line 360

def ignored_columns=(columns)
  reload_schema_from_cache
  @ignored_columns = columns.map(&:to_s).freeze
end

#next_sequence_value ⇒ Object

Returns the next value that will be used as the primary key on an insert statement.



405
406
407
 
# File 'activerecord/lib/active_record/model_schema.rb', line 405

def next_sequence_value
  connection.next_sequence_value(sequence_name)
end

#prefetch_primary_key? ⇒ Boolean

Determines if the primary key values should be selected from their corresponding sequence before the insert statement.

Returns:

  • (Boolean) 


399
400
401
 
# File 'activerecord/lib/active_record/model_schema.rb', line 399

def prefetch_primary_key?
  connection.prefetch_primary_key?(table_name)
end

#protected_environments ⇒ Object

The array of names of environments where destructive actions should be prohibited. By default, the value is ["production"].



306
307
308
309
310
311
312
 
# File 'activerecord/lib/active_record/model_schema.rb', line 306

def protected_environments
  if defined?(@protected_environments)
    @protected_environments
  else
    superclass.protected_environments
  end
end

#protected_environments=(environments) ⇒ Object

Sets an array of names of environments where destructive actions should be prohibited.



315
316
317
 
# File 'activerecord/lib/active_record/model_schema.rb', line 315

def protected_environments=(environments)
  @protected_environments = environments.map(&:to_s)
end

#quoted_table_name ⇒ Object

Returns a quoted version of the table name, used to construct SQL statements.



281
282
283
 
# File 'activerecord/lib/active_record/model_schema.rb', line 281

def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end

#real_inheritance_column=(value) ⇒ Object

:nodoc:



319
320
321
 
# File 'activerecord/lib/active_record/model_schema.rb', line 319

def real_inheritance_column=(value) # :nodoc:
  self._inheritance_column = value.to_s
end

#reset_column_information ⇒ Object

Resets all the cached information about columns, which will cause them to be reloaded on the next request.

The most common usage pattern for this method is probably in a migration, when just after creating a table you want to populate it with some default values, e.g.:

class CreateJobLevels < ActiveRecord::Migration[7.1]
  def up
    create_table :job_levels do |t|
      t.integer :id
      t.string :name

      t.timestamps
    end

    JobLevel.reset_column_information
    %w{assistant executive manager director}.each do |type|
      JobLevel.create(name: type)
    end
  end

  def down
    drop_table :job_levels
  end
end



547
548
549
550
551
552
553
554
 
# File 'activerecord/lib/active_record/model_schema.rb', line 547

def reset_column_information
  connection.clear_cache!
  ([self] + descendants).each(&:undefine_attribute_methods)
  connection.schema_cache.clear_data_source_cache!(table_name)

  reload_schema_from_cache
  initialize_find_by_cache
end

#reset_sequence_name ⇒ Object

:nodoc:



373
374
375
376
 
# File 'activerecord/lib/active_record/model_schema.rb', line 373

def reset_sequence_name # :nodoc:
  @explicit_sequence_name = false
  @sequence_name          = connection.default_sequence_name(table_name, primary_key)
end

#reset_table_name ⇒ Object

Computes the table name, (re)sets it internally, and returns it.



286
287
288
289
290
291
292
293
294
 
# File 'activerecord/lib/active_record/model_schema.rb', line 286

def reset_table_name # :nodoc:
  self.table_name = if abstract_class?
    superclass == Base ? nil : superclass.table_name
  elsif superclass.abstract_class?
    superclass.table_name || compute_table_name
  else
    compute_table_name
  end
end

#sequence_name ⇒ Object 



365
366
367
368
369
370
371
 
# File 'activerecord/lib/active_record/model_schema.rb', line 365

def sequence_name
  if base_class?
    @sequence_name ||= reset_sequence_name
  else
    (@sequence_name ||= nil) || base_class.sequence_name
  end
end

#sequence_name=(value) ⇒ Object

Sets the name of the sequence to use when generating ids to the given value, or (if the value is nil or false) to the value returned by the given block. This is required for Oracle and is useful for any database which relies on sequences for primary key generation.

If a sequence name is not explicitly set when using Oracle, it will default to the commonly used pattern of: ##table_name_seq

If a sequence name is not explicitly set when using PostgreSQL, it will discover the sequence corresponding to your primary key for you.

class Project < ActiveRecord::Base
  self.sequence_name = "projectseq"   # default would have been "project_seq"
end



392
393
394
395
 
# File 'activerecord/lib/active_record/model_schema.rb', line 392

def sequence_name=(value)
  @sequence_name          = value.to_s
  @explicit_sequence_name = true
end

#symbol_column_to_string(name_symbol) ⇒ Object

:nodoc:



506
507
508
509
 
# File 'activerecord/lib/active_record/model_schema.rb', line 506

def symbol_column_to_string(name_symbol) # :nodoc:
  @symbol_column_to_string_name_hash ||= column_names.index_by(&:to_sym)
  @symbol_column_to_string_name_hash[name_symbol]
end

#table_exists? ⇒ Boolean

Indicates whether the table associated with this class exists

Returns:

  • (Boolean) 


410
411
412
 
# File 'activerecord/lib/active_record/model_schema.rb', line 410

def table_exists?
  connection.schema_cache.data_source_exists?(table_name)
end

#table_name ⇒ Object

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ActiveRecord::Base. So if the hierarchy looks like: Reply < Message < ActiveRecord::Base, then Message is used to guess the table name even when called on Reply. The rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections. You can add new inflections in config/initializers/inflections.rb.

Nested classes are given table names prefixed by the singular form of the parent’s table name. Enclosing modules are not considered.

Examples

class Invoice < ActiveRecord::Base
end

file                  class               table_name
invoice.rb            Invoice             invoices

class Invoice < ActiveRecord::Base
  class Lineitem < ActiveRecord::Base
  end
end

file                  class               table_name
invoice.rb            Invoice::Lineitem   invoice_lineitems

module Invoice
  class Lineitem < ActiveRecord::Base
  end
end

file                  class               table_name
invoice/lineitem.rb   Invoice::Lineitem   lineitems

Additionally, the class-level table_name_prefix is prepended and the table_name_suffix is appended. So if you have “myapp_” as a prefix, the table name guess for an Invoice class becomes “myapp_invoices”. Invoice::Lineitem becomes “myapp_invoice_lineitems”.

Active Model Naming’s model_name is the base name used to guess the table name. In case a custom Active Model Name is defined, it will be used for the table name as well:

class PostRecord < ActiveRecord::Base
  class << self
    def model_name
      ActiveModel::Name.new(self, nil, "Post")
    end
  end
end

PostRecord.table_name
# => "posts"

You can also set your own table name explicitly:

class Mouse < ActiveRecord::Base
  self.table_name = "mice"
end



255
256
257
258
 
# File 'activerecord/lib/active_record/model_schema.rb', line 255

def table_name
  reset_table_name unless defined?(@table_name)
  @table_name
end

#table_name=(value) ⇒ Object

Sets the table name explicitly. Example:

class Project < ActiveRecord::Base
  self.table_name = "project"
end



265
266
267
268
269
270
271
272
273
274
275
276
277
278
 
# File 'activerecord/lib/active_record/model_schema.rb', line 265

def table_name=(value)
  value = value && value.to_s

  if defined?(@table_name)
    return if value == @table_name
    reset_column_information if connected?
  end

  @table_name        = value
  @quoted_table_name = nil
  @arel_table        = nil
  @sequence_name     = nil unless defined?(@explicit_sequence_name) && @explicit_sequence_name
  @predicate_builder = nil
end

#type_for_attribute(attr_name, &block) ⇒ Object

Returns the type of the attribute with the given name, after applying all modifiers. This method is the only valid source of information for anything related to the types of a model’s attributes. This method will access the database and load the model’s schema if it is required.

The return value of this method will implement the interface described by ActiveModel::Type::Value (though the object itself may not subclass it).

attr_name The name of the attribute to retrieve the type for. Must be a string or a symbol.



458
459
460
461
462
463
464
465
466
467
 
# File 'activerecord/lib/active_record/model_schema.rb', line 458

def type_for_attribute(attr_name, &block)
  attr_name = attr_name.to_s
  attr_name = attribute_aliases[attr_name] || attr_name

  if block
    attribute_types.fetch(attr_name, &block)
  else
    attribute_types[attr_name]
  end
end

#yaml_encoder ⇒ Object

:nodoc:



443
444
445
 
# File 'activerecord/lib/active_record/model_schema.rb', line 443

def yaml_encoder # :nodoc:
  @yaml_encoder ||= ActiveModel::AttributeSet::YAMLEncoder.new(attribute_types)
end