module ActiveRecord::ModelSchema::ClassMethods

# File activerecord/lib/active_record/model_schema.rb, line 249
def column_defaults
  _default_attributes.dup.to_hash
end

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

# File activerecord/lib/active_record/model_schema.rb, line 259
def column_names
  @column_names ||= columns.map { |column| column.name }
end

Returns an array of column names as strings.

# File activerecord/lib/active_record/model_schema.rb, line 265
def content_columns
  @content_columns ||= columns.reject { |c| c.name == primary_key || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
end

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.

# File activerecord/lib/active_record/model_schema.rb, line 186
def inheritance_column
  (@inheritance_column ||= nil) || superclass.inheritance_column
end

Defines the name of the table column which will store the class name on single-table inheritance situations.

The default inheritance column name is type, which means it's a reserved word inside Active Record. To be able to use single-table inheritance with another column name, or to use the column type in your own model for something else, you can set inheritance_column:

self.inheritance_column = 'zoink'

# File activerecord/lib/active_record/model_schema.rb, line 191
def inheritance_column=(value)
  @inheritance_column = value.to_s
  @explicit_inheritance_column = true
end

Sets the value of #inheritance_column

# File activerecord/lib/active_record/model_schema.rb, line 154
def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end

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

# File activerecord/lib/active_record/model_schema.rb, line 295
def reset_column_information
  connection.clear_cache!
  undefine_attribute_methods
  connection.schema_cache.clear_table_cache!(table_name)

  @arel_engine        = nil
  @column_names       = nil
  @column_types       = nil
  @content_columns    = nil
  @default_attributes = nil
  @inheritance_column = nil unless defined?(@explicit_inheritance_column) && @explicit_inheritance_column
  @relation           = nil

  initialize_find_by_cache
end

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, eg:

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

# File activerecord/lib/active_record/model_schema.rb, line 223
def sequence_name=(value)
  @sequence_name          = value.to_s
  @explicit_sequence_name = true
end

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

# File activerecord/lib/active_record/model_schema.rb, line 229
def table_exists?
  connection.schema_cache.table_exists?(table_name)
end

Indicates whether the table associated with this class exists

# File activerecord/lib/active_record/model_schema.rb, line 125
def table_name
  reset_table_name unless defined?(@table_name)
  @table_name
end

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”.

You can also set your own table name explicitly:

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

Alternatively, you can override the #table_name method to define your own computation. (Possibly using super to manipulate the default table name.) Example:

class Post < ActiveRecord::Base
  def self.table_name
    "special_" + super
  end
end
Post.table_name # => "special_posts"

# File activerecord/lib/active_record/model_schema.rb, line 138
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
  @relation          = Relation.create(self, arel_table)
end

Sets the table name explicitly. Example:

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

You can also just define your own self.table_name method; see the documentation for ActiveRecord::Base#table_name.