Module: ActiveRecord::ModelSchema::ClassMethods

Relationships & Source Files
Defined in:	activerecord/lib/active_record/model_schema.rb

Instance Attribute Summary

#ignored_columns rw

The list of columns names the model should ignore.
#ignored_columns=(columns) rw

Sets the columns names the model should ignore.
#only_columns rw

The list of columns names the model should allow.
#only_columns=(columns) rw
#prefetch_primary_key? ⇒ Boolean readonly

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

The array of names of environments where destructive actions should be prohibited.
#protected_environments=(environments) rw

Sets an array of names of environments where destructive actions should be prohibited.
#sequence_name rw
#sequence_name=(value) rw

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.
#table_exists? ⇒ Boolean readonly

Indicates whether the table associated with this class exists.
#table_name rw

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ::ActiveRecord::Base.
#table_name=(value) rw

Sets the table name explicitly.
#schema_loaded? ⇒ Boolean readonly private
#real_inheritance_column=(value) writeonly Internal use only

Instance Method Summary

#column_defaults

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

Returns the column object for the named attribute.
#column_names

Returns an array of column names as strings.
#columns
#content_columns

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.
#load_schema

Load the model's schema information either from the schema cache or directly from the database.
#next_sequence_value

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

Returns a quoted version of the table name.
#reset_column_information

Resets all the cached information about columns, which will cause them to be reloaded on the next request.
#initialize_load_schema_monitor protected
#reload_schema_contexts_from_cache protected
#reload_schema_from_cache(recursive = true) protected
#check_model_columns(columns_present) private
#compute_table_name private

Computes and returns a table name according to default conventions.
#inherited(child_class) private
#load_schema! private
#type_for_column(column) private
#undecorated_table_name(model_name) private

Guesses the table name, but does not decorate it with prefix and suffix information.
#_returning_columns_for_insert(connection) Internal use only
#_returning_columns_for_update(connection) Internal use only
#attributes_builder Internal use only
#build_schema_context Internal use only
#columns_hash Internal use only
#full_table_name_prefix Internal use only
#full_table_name_suffix Internal use only
#reset_sequence_name Internal use only
#reset_table_name Internal use only

Computes the table name, (re)sets it internally, and returns it.
#schema_context Internal use only

Instance Attribute Details

#ignored_columns (rw)

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.

[ GitHub ]

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


def ignored_columns
  @ignored_columns || superclass.ignored_columns
end

#ignored_columns=(columns) (rw)

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 403


def ignored_columns=(columns)
  check_model_columns(@only_columns.present?)
  reload_schema_from_cache
  @ignored_columns = columns.map(&:to_s).freeze
end

#only_columns (rw)

The list of columns names the model should allow. Only columns are used to define attribute accessors, and are referenced in SQL queries.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 368


def only_columns
  @only_columns || superclass.only_columns
end

#only_columns=(columns) (rw)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 409


def only_columns=(columns)
  check_model_columns(@ignored_columns.present?)
  reload_schema_from_cache
  @only_columns = columns.map(&:to_s).freeze
end

#prefetch_primary_key? ⇒ `Boolean` (readonly)

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 449


def prefetch_primary_key?
  with_connection { |c| c.prefetch_primary_key?(table_name) }
end

#protected_environments (rw)

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

[ GitHub ]

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


def protected_environments
  ActiveRecord.deprecator.warn <<~MSG
    ActiveRecord::Base.protected_environments is deprecated in favor of
    ActiveRecord.protected_environments and will be removed in Rails 9.0.
  MSG

  if self == ActiveRecord::Base
    ActiveRecord.protected_environments
  elsif defined?(@protected_environments)
    @protected_environments
  else
    superclass.protected_environments
  end
end

#protected_environments=(environments) (rw)

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 343


def protected_environments=(environments)
  ActiveRecord.deprecator.warn <<~MSG
    ActiveRecord::Base.protected_environments= is deprecated in favor of
    ActiveRecord.protected_environments= and will be removed in Rails 9.0.
  MSG

  if self == ActiveRecord::Base
    ActiveRecord.protected_environments = environments
  else
    @protected_environments = environments.map(&:to_s)
  end
end

#real_inheritance_column=(value) (writeonly)

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 356


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

#schema_loaded? ⇒ `Boolean` (readonly, private)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 618


def schema_loaded?
  @schema_context&.schema_loaded? || false
end

#sequence_name (rw)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 415


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

#sequence_name=(value) (rw)

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 442


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

#table_exists? ⇒ `Boolean` (readonly)

Indicates whether the table associated with this class exists

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 460


def table_exists?
  schema_cache.data_source_exists?(table_name)
end

#table_name (rw)

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 ActiveRecord::ModelSchema.table_name_prefix is prepended and the ActiveRecord::ModelSchema.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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 272


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

#table_name=(value) (rw)

Sets the table name explicitly. Example:

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

[ GitHub ]

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


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

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

  @table_name        = value
  @arel_table        = Arel::Table.new(klass: self)
  @predicate_builder = PredicateBuilder.new(TableMetadata.new(self, @arel_table)) if renaming
  @sequence_name     = nil unless @explicit_sequence_name
end

Instance Method Details

#_returning_columns_for_insert(connection)

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 476


def _returning_columns_for_insert(connection) # :nodoc:
  @_returning_columns_for_insert || ActiveSupport::Ractors.on_main(self) do
    @_returning_columns_for_insert ||= schema_context._returning_columns_for_insert(connection)
  end
end

#_returning_columns_for_update(connection)

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 482


def _returning_columns_for_update(connection) # :nodoc:
  @_returning_columns_for_update || ActiveSupport::Ractors.on_main(self) do
    @_returning_columns_for_update ||= schema_context._returning_columns_for_update(connection)
  end
end

#attributes_builder

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 464


def attributes_builder # :nodoc:
  schema_context.attributes.builder
end

#build_schema_context

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 209


def build_schema_context # :nodoc:
  ActiveRecord::ModelSchema::SchemaContext.new(self)
end

#check_model_columns(columns_present) (private)

Raises:

(ArgumentError)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 659


def check_model_columns(columns_present)
  raise ArgumentError, "You can not use both only_columns and ignored_columns in the same model." if columns_present
end

#column_defaults

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 510


def column_defaults
  schema_context.attributes.column_defaults
end

#column_for_attribute(name)

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>, ...>

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 501


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

#column_names

Returns an array of column names as strings.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 515


def column_names
  schema_context.column_names
end

#columns

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 472


def columns
  schema_context.columns
end

#columns_hash

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 468


def columns_hash # :nodoc:
  schema_context.columns_hash
end

#compute_table_name (private)

Computes and returns a table name according to default conventions.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 633


def compute_table_name
  if base_class?
    # Nested classes are prefixed with singular parent table name.
    if module_parent < Base && !module_parent.abstract_class?
      contained = module_parent.table_name
      contained = contained.singularize if module_parent.pluralize_table_names
      contained += "_"
    end

    "#{full_table_name_prefix}#{contained}#{undecorated_table_name(model_name)}#{full_table_name_suffix}".freeze
  else
    # STI subclasses always use their superclass's table.
    base_class.table_name
  end
end

#content_columns

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.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 521


def content_columns
  schema_context.content_columns
end

#full_table_name_prefix

This method is for internal use only.

[ GitHub ]

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


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

This method is for internal use only.

[ GitHub ]

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


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

#inherited(child_class) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 608


def inherited(child_class)
  super
  child_class.initialize_load_schema_monitor
  child_class.reload_schema_from_cache(false)
  child_class.class_eval do
    @ignored_columns = nil
    @only_columns = nil
  end
end

#initialize_load_schema_monitor (protected)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 582


def initialize_load_schema_monitor
  @load_schema_monitor = Monitor.new
end

#load_schema

Load the model's schema information either from the schema cache or directly from the database.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 562


def load_schema
  return if schema_loaded?

  @load_schema_monitor.synchronize do
    unless schema_loaded? || @schema_context
      @schema_context = build_schema_context
      @schema_context.load_schema!
      ActiveSupport::Ractors.make_shareable(@schema_context)
      unless @schema_hooks_loaded
        load_schema!
        @schema_hooks_loaded = true
      end
    end
  rescue
    reload_schema_from_cache # If the schema loading failed half way through, we must reset the state.
    raise
  end
end

#load_schema! (private)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 622


def load_schema!
  # The current schema context handles the default schema load.
end

#next_sequence_value

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 455


def next_sequence_value
  with_connection { |c| c.next_sequence_value(sequence_name) }
end

#quoted_table_name

Returns a quoted version of the table name.

[ GitHub ]

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


def quoted_table_name
  adapter_class.quote_table_name(table_name)
end

#reload_schema_contexts_from_cache (protected)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 601


def reload_schema_contexts_from_cache
  @schema_context = nil
  @_returning_columns_for_insert = nil
  @_returning_columns_for_update = nil
end

#reload_schema_from_cache(recursive = true) (protected)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 586


def reload_schema_from_cache(recursive = true)
  @schema_hooks_loaded = false
  @arel_table = Arel::Table.new(klass: self)
  @predicate_builder = PredicateBuilder.new(TableMetadata.new(self, @arel_table)) unless self == Base
  @attribute_names = nil

  reload_schema_contexts_from_cache

  if recursive
    subclasses.each do |descendant|
      descendant.send(:reload_schema_from_cache)
    end
  end
end

#reset_column_information

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 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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 551


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

  reload_schema_from_cache
  initialize_find_by_cache
end

#reset_sequence_name

This method is for internal use only.

[ GitHub ]

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


def reset_sequence_name # :nodoc:
  @explicit_sequence_name = false
  @sequence_name          = with_connection { |c| c.default_sequence_name(table_name, primary_key) }
end

#reset_table_name

This method is for internal use only.

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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 303


def reset_table_name # :nodoc:
  ActiveSupport::Ractors.on_main(self) do
    self.table_name = if self == Base
      nil
    elsif abstract_class?
      superclass.table_name
    elsif superclass.abstract_class?
      superclass.table_name || compute_table_name
    else
      compute_table_name
    end
  end
end

#schema_context

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 203


def schema_context # :nodoc:
  return @schema_context if schema_loaded?
  load_schema
  @schema_context
end

#type_for_column(column) (private)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 649


def type_for_column(column)
  type = column.cast_type

  if immutable_strings_by_default && type.respond_to?(:to_immutable_string)
    type = type.to_immutable_string
  end

  type
end

#undecorated_table_name(model_name) (private)

Guesses the table name, but does not decorate it with prefix and suffix information.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 627


def undecorated_table_name(model_name)
  table_name = model_name.to_s.demodulize.underscore
  pluralize_table_names ? table_name.pluralize : table_name
end

Module: ActiveRecord::ModelSchema::ClassMethods

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#ignored_columns (rw)

#ignored_columns=(columns) (rw)

#only_columns (rw)

#only_columns=(columns) (rw)

#prefetch_primary_key? ⇒ Boolean (readonly)

#protected_environments (rw)

#protected_environments=(environments) (rw)

#real_inheritance_column=(value) (writeonly)

#schema_loaded? ⇒ Boolean (readonly, private)

#sequence_name (rw)

#sequence_name=(value) (rw)

#table_exists? ⇒ Boolean (readonly)

#table_name (rw)

Examples

#table_name=(value) (rw)

Instance Method Details

#_returning_columns_for_insert(connection)

#_returning_columns_for_update(connection)

#attributes_builder

#build_schema_context

#check_model_columns(columns_present) (private)

#column_defaults

#column_for_attribute(name)

#column_names

#columns

#columns_hash

#compute_table_name (private)

#content_columns

#full_table_name_prefix

#full_table_name_suffix

#inherited(child_class) (private)

#initialize_load_schema_monitor (protected)

#load_schema

#load_schema! (private)

#next_sequence_value

#quoted_table_name

#reload_schema_contexts_from_cache (protected)

#reload_schema_from_cache(recursive = true) (protected)

#reset_column_information

#reset_sequence_name

#reset_table_name

#schema_context

#type_for_column(column) (private)

#undecorated_table_name(model_name) (private)

#prefetch_primary_key? ⇒ `Boolean` (readonly)

#schema_loaded? ⇒ `Boolean` (readonly, private)

#table_exists? ⇒ `Boolean` (readonly)