Methods

Instance Public methods

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.

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 493
      def column_defaults
        load_schema
        @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze
      end
πŸ”Ž See on GitHub

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>, ...>
πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 484
      def column_for_attribute(name)
        name = name.to_s
        columns_hash.fetch(name) do
          ConnectionAdapters::NullColumn.new(name)
        end
      end
πŸ”Ž See on GitHub

column_names()

Returns an array of column names as strings.

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 504
      def column_names
        @column_names ||= columns.map(&:name).freeze
      end
πŸ”Ž See on GitHub

columns()

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 429
      def columns
        load_schema
        @columns ||= columns_hash.values.freeze
      end
πŸ”Ž See on GitHub

content_columns()

Returns an array of column objects where the primary id, all columns ending in β€œ_id” or β€œ_count”, and columns used for single table inheritance have been removed.

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 515
      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
πŸ”Ž See on GitHub

ignored_columns()

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.

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 327
      def ignored_columns
        @ignored_columns || superclass.ignored_columns
      end
πŸ”Ž See on GitHub

ignored_columns=(columns)

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 β€œcategory” 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 β€œcategory”, 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
πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 362
      def ignored_columns=(columns)
        reload_schema_from_cache
        @ignored_columns = columns.map(&:to_s).freeze
      end
πŸ”Ž See on GitHub

next_sequence_value()

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

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 407
      def next_sequence_value
        connection.next_sequence_value(sequence_name)
      end
πŸ”Ž See on GitHub

prefetch_primary_key?()

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

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 401
      def prefetch_primary_key?
        connection.prefetch_primary_key?(table_name)
      end
πŸ”Ž See on GitHub

protected_environments()

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

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 308
      def protected_environments
        if defined?(@protected_environments)
          @protected_environments
        else
          superclass.protected_environments
        end
      end
πŸ”Ž See on GitHub

protected_environments=(environments)

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

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 317
      def protected_environments=(environments)
        @protected_environments = environments.map(&:to_s)
      end
πŸ”Ž See on GitHub

quoted_table_name()

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

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 281
      def quoted_table_name
        @quoted_table_name ||= connection.quote_table_name(table_name)
      end
πŸ”Ž See on GitHub

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[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
πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 549
      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
πŸ”Ž See on GitHub

sequence_name()

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 367
      def sequence_name
        if base_class?
          @sequence_name ||= reset_sequence_name
        else
          (@sequence_name ||= nil) || base_class.sequence_name
        end
      end
πŸ”Ž See on GitHub

sequence_name=(value)

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
πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 394
      def sequence_name=(value)
        @sequence_name          = value.to_s
        @explicit_sequence_name = true
      end
πŸ”Ž See on GitHub

table_exists?()

Indicates whether the table associated with this class exists

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 412
      def table_exists?
        connection.schema_cache.data_source_exists?(table_name)
      end
πŸ”Ž See on GitHub

table_name()

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 β€œmyapp_” as a prefix, the table name guess for an Invoice class becomes β€œmyapp_invoices”. Invoice::Lineitem becomes β€œmyapp_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
πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 255
      def table_name
        reset_table_name unless defined?(@table_name)
        @table_name
      end
πŸ”Ž See on GitHub

table_name=(value)

Sets the table name explicitly. Example:

class Project < ActiveRecord::Base
  self.table_name = "project"
end
πŸ“ Source code
# 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
πŸ”Ž See on GitHub

type_for_attribute(attr_name, &block)

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.

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 460
      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
πŸ”Ž See on GitHub

Instance Protected methods

initialize_load_schema_monitor()

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 573
        def initialize_load_schema_monitor
          @load_schema_monitor = Monitor.new
        end
πŸ”Ž See on GitHub

reload_schema_from_cache(recursive = true)

πŸ“ Source code
# File activerecord/lib/active_record/model_schema.rb, line 577
        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
          @attribute_types = nil
          @content_columns = nil
          @default_attributes = 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
πŸ”Ž See on GitHub