module ActiveRecord::ModelSchema::ClassMethods

def _returning_columns_for_insert(connection) # :nodoc:

:nodoc: 
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

def attributes_builder # :nodoc:

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

def column_defaults

default values when instantiating the Active Record object for this table.
Returns a hash where the keys are column names and the values are 
def column_defaults
  load_schema
  @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze
end

def column_for_attribute(name)

# => #, ...>
person.column_for_attribute(:nothing)

# => #
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
person = Person.new

end
class Person < ActiveRecord::Base

named attribute does not exist.
Returns an ActiveRecord::ConnectionAdapters::NullColumn if the
Returns the column object for the named attribute. 
def column_for_attribute(name)
  name = name.to_s
  columns_hash.fetch(name) do
    ConnectionAdapters::NullColumn.new(name)
  end
end

def column_names

Returns an array of column names as strings. 
def column_names
  @column_names ||= columns.map(&:name).freeze
end

def columns 

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

def columns_hash # :nodoc:

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

def compute_table_name

Computes and returns a table name according to default conventions. 
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

def content_columns

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

def full_table_name_prefix # :nodoc:

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

def full_table_name_suffix # :nodoc:

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

def ignored_columns

accessors defined, and won't be referenced in SQL queries.
The list of columns names the model should ignore. Ignored columns won't have attribute 
def ignored_columns
  @ignored_columns || superclass.ignored_columns
end

def ignored_columns=(columns)

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

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

Project.columns_hash["category"] => nil

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

end
self.ignored_columns += [:category]

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

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

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

accessors defined, and won't be referenced in SQL queries.
Sets the columns names the model should ignore. Ignored columns won't have attribute 
def ignored_columns=(columns)
  reload_schema_from_cache
  @ignored_columns = columns.map(&:to_s).freeze
end

def inherited(child_class) 

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

def initialize_load_schema_monitor 

def initialize_load_schema_monitor
  @load_schema_monitor = Monitor.new
end

def load_schema

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

def load_schema! 

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

def next_sequence_value

an insert statement.
Returns the next value that will be used as the primary key on 
def next_sequence_value
  with_connection { |c| c.next_sequence_value(sequence_name) }
end

def prefetch_primary_key?

corresponding sequence before the insert statement.
Determines if the primary key values should be selected from their 
def prefetch_primary_key?
  with_connection { |c| c.prefetch_primary_key?(table_name) }
end

def protected_environments

the value is ["production"].
The array of names of environments where destructive actions should be prohibited. By default, 
def protected_environments
  if defined?(@protected_environments)
    @protected_environments
  else
    superclass.protected_environments
  end
end

def protected_environments=(environments)

Sets an array of names of environments where destructive actions should be prohibited. 
def protected_environments=(environments)
  @protected_environments = environments.map(&:to_s)
end

def quoted_table_name

Returns a quoted version of the table name. 
def quoted_table_name
  adapter_class.quote_table_name(table_name)
end

def real_inheritance_column=(value) # :nodoc:

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

def reload_schema_from_cache(recursive = true) 

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

def reset_column_information

end
end
drop_table :job_levels
def down

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

end
t.timestamps

t.string :name
t.integer :id
create_table :job_levels do |t|
def up
class CreateJobLevels < ActiveRecord::Migration[8.0]

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

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

def reset_sequence_name # :nodoc:

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

def reset_table_name # :nodoc:

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

def schema_loaded? 

def schema_loaded?
  @schema_loaded
end

def sequence_name 

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

def sequence_name=(value)

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

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

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

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

def symbol_column_to_string(name_symbol) # :nodoc:

:nodoc: 
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

def table_exists?

Indicates whether the table associated with this class exists 
def table_exists?
  schema_cache.data_source_exists?(table_name)
end

def table_name

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

You can also set your own table name explicitly:

# => "posts"
PostRecord.table_name

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

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

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

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

end
end
class Lineitem < ActiveRecord::Base
module Invoice

invoice.rb Invoice::Lineitem invoice_lineitems
file class table_name

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

invoice.rb Invoice invoices
file class table_name

end
class Invoice < ActiveRecord::Base

==== Examples

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

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

def table_name=(value)

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

Sets the table name explicitly. Example: 
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

def type_for_column(connection, column) 

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

def undecorated_table_name(model_name)

Guesses the table name, but does not decorate it with prefix and suffix information. 
def undecorated_table_name(model_name)
  table_name = model_name.to_s.demodulize.underscore
  pluralize_table_names ? table_name.pluralize : table_name
end

def yaml_encoder # :nodoc:

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