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.
#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_from_cache(recursive = true) protected
#compute_table_name private

Computes and returns a table name according to default conventions.
#inherited(child_class) private
#load_schema! private
#type_for_column(connection, 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
#attributes_builder 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.
#symbol_column_to_string(name_symbol) Internal use only
#yaml_encoder 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 331


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 366


def ignored_columns=(columns)
  reload_schema_from_cache
  @ignored_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 405


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 312


def protected_environments
  if 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 321


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

#real_inheritance_column=(value) (writeonly)

This method is for internal use only.

[ GitHub ]

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


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 583


def schema_loaded?
  @schema_loaded
end

#sequence_name (rw)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 371


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 398


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 416


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 260


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 270


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
  @arel_table        = nil
  @sequence_name     = nil unless @explicit_sequence_name
  @predicate_builder = nil
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 436


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

    auto_populated_columns.empty? ? Array(primary_key) : auto_populated_columns
  end
end

#attributes_builder

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 420


def attributes_builder # :nodoc:
  @attributes_builder ||= begin
    defaults = _default_attributes.except(*(column_names - [primary_key]))
    ActiveModel::AttributeSet::Builder.new(attribute_types, defaults)
  end
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 472


def column_defaults
  load_schema
  @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze
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 463


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 478


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

#columns

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 432


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

#columns_hash

This method is for internal use only.

[ GitHub ]

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


def columns_hash # :nodoc:
  load_schema unless @columns_hash
  @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 606


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}"
  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 489


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

This method is for internal use only.

[ GitHub ]

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


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 306


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 574


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
  end
end

#initialize_load_schema_monitor (protected)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 549


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 534


def load_schema
  return if schema_loaded?
  @load_schema_monitor.synchronize do
    return if schema_loaded?

    load_schema!

    @schema_loaded = true
  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 587


def load_schema!
  unless table_name
    raise ActiveRecord::TableNotSpecified, "#{self} has no table configured. Set one with #{self}.table_name="
  end

  columns_hash = schema_cache.columns_hash(table_name)
  columns_hash = columns_hash.except(*ignored_columns) unless ignored_columns.empty?
  @columns_hash = columns_hash.freeze

  _default_attributes # Precompute to cache DB-dependent attribute types
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 411


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 285


def quoted_table_name
  adapter_class.quote_table_name(table_name)
end

#reload_schema_from_cache(recursive = true) (protected)

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 553


def reload_schema_from_cache(recursive = true)
  @_returning_columns_for_insert = nil
  @arel_table = nil
  @column_names = nil
  @symbol_column_to_string_name_hash = nil
  @content_columns = nil
  @column_defaults = nil
  @attributes_builder = nil
  @columns = nil
  @columns_hash = nil
  @schema_loaded = false
  @attribute_names = nil
  @yaml_encoder = nil
  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[8.1]
  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

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 523


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 379


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 290


def reset_table_name # :nodoc:
  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

#symbol_column_to_string(name_symbol)

This method is for internal use only.

[ GitHub ]

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


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

#type_for_column(connection, column) (private)

[ GitHub ]

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


def type_for_column(connection, column)
  type = connection.lookup_cast_type_from_column(column)

  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 600


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

#yaml_encoder

This method is for internal use only.

[ GitHub ]

# File 'activerecord/lib/active_record/model_schema.rb', line 446


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

Module: ActiveRecord::ModelSchema::ClassMethods

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#ignored_columns (rw)

#ignored_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)

#attributes_builder

#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_from_cache(recursive = true) (protected)

#reset_column_information

#reset_sequence_name

#reset_table_name

#symbol_column_to_string(name_symbol)

#type_for_column(connection, column) (private)

#undecorated_table_name(model_name) (private)

#yaml_encoder

#prefetch_primary_key? ⇒ `Boolean` (readonly)

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

#table_exists? ⇒ `Boolean` (readonly)