module ActiveRecord::ModelSchema::ClassMethods
Public Instance Methods
Returns a hash where the keys are column names and the values are default values when instantiating the Active Record object for this table.
# File lib/active_record/model_schema.rb, line 469 def column_defaults load_schema @column_defaults ||= _default_attributes.deep_dup.to_hash.freeze end
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>, ...>
# File lib/active_record/model_schema.rb, line 460 def column_for_attribute(name) name = name.to_s columns_hash.fetch(name) do ConnectionAdapters::NullColumn.new(name) end end
Returns an array of column names as strings.
# File lib/active_record/model_schema.rb, line 480 def column_names @column_names ||= columns.map(&:name).freeze end
# File lib/active_record/model_schema.rb, line 411 def columns load_schema @columns ||= columns_hash.values.freeze 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 lib/active_record/model_schema.rb, line 491 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
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.
# File lib/active_record/model_schema.rb, line 305 def ignored_columns if defined?(@ignored_columns) @ignored_columns else superclass.ignored_columns end end
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
# File lib/active_record/model_schema.rb, line 344 def ignored_columns=(columns) reload_schema_from_cache @ignored_columns = columns.map(&:to_s).freeze end
Returns the next value that will be used as the primary key on an insert statement.
# File lib/active_record/model_schema.rb, line 389 def next_sequence_value connection.next_sequence_value(sequence_name) end
Determines if the primary key values should be selected from their corresponding sequence before the insert statement.
# File lib/active_record/model_schema.rb, line 383 def prefetch_primary_key? connection.prefetch_primary_key?(table_name) end
The array of names of environments where destructive actions should be prohibited. By default, the value is ["production"]
.
# File lib/active_record/model_schema.rb, line 286 def protected_environments if defined?(@protected_environments) @protected_environments else superclass.protected_environments end end
Sets an array of names of environments where destructive actions should be prohibited.
# File lib/active_record/model_schema.rb, line 295 def protected_environments=(environments) @protected_environments = environments.map(&:to_s) end
Returns a quoted version of the table name, used to construct SQL statements.
# File lib/active_record/model_schema.rb, line 261 def quoted_table_name @quoted_table_name ||= connection.quote_table_name(table_name) 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, e.g.:
class CreateJobLevels < ActiveRecord::Migration[7.0] 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 lib/active_record/model_schema.rb, line 525 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
# File lib/active_record/model_schema.rb, line 349 def sequence_name if base_class? @sequence_name ||= reset_sequence_name else (@sequence_name ||= nil) || base_class.sequence_name end 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 lib/active_record/model_schema.rb, line 376 def sequence_name=(value) @sequence_name = value.to_s @explicit_sequence_name = true end
Indicates whether the table associated with this class exists
# File lib/active_record/model_schema.rb, line 394 def table_exists? connection.schema_cache.data_source_exists?(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”.
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
# File lib/active_record/model_schema.rb, line 235 def table_name reset_table_name unless defined?(@table_name) @table_name end
Sets the table name explicitly. Example:
class Project < ActiveRecord::Base self.table_name = "project" end
# File lib/active_record/model_schema.rb, line 245 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
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.
# File lib/active_record/model_schema.rb, line 436 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
Protected Instance Methods
# File lib/active_record/model_schema.rb, line 535 def initialize_load_schema_monitor @load_schema_monitor = Monitor.new end
Private Instance Methods
# File lib/active_record/model_schema.rb, line 625 def _convert_type_from_options(type) if immutable_strings_by_default && type.respond_to?(:to_immutable_string) type.to_immutable_string else type end end
Computes and returns a table name according to default conventions.
# File lib/active_record/model_schema.rb, line 609 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' table. base_class.table_name end end
# File lib/active_record/model_schema.rb, line 540 def inherited(child_class) super child_class.initialize_load_schema_monitor end
# File lib/active_record/model_schema.rb, line 549 def load_schema return if schema_loaded? @load_schema_monitor.synchronize do return if defined?(@columns_hash) && @columns_hash 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
# File lib/active_record/model_schema.rb, line 563 def load_schema! unless table_name raise ActiveRecord::TableNotSpecified, "#{self} has no table configured. Set one with #{self}.table_name=" end columns_hash = connection.schema_cache.columns_hash(table_name) columns_hash = columns_hash.except(*ignored_columns) unless ignored_columns.empty? @columns_hash = columns_hash.freeze @columns_hash.each do |name, column| type = connection.lookup_cast_type_from_column(column) type = _convert_type_from_options(type) define_attribute( name, type, default: column.default, user_provided_default: false ) end end
# File lib/active_record/model_schema.rb, line 583 def reload_schema_from_cache @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 subclasses.each do |descendant| descendant.send(:reload_schema_from_cache) end end
# File lib/active_record/model_schema.rb, line 545 def schema_loaded? defined?(@schema_loaded) && @schema_loaded end
Guesses the table name, but does not decorate it with prefix and suffix information.
# File lib/active_record/model_schema.rb, line 603 def undecorated_table_name(model_name) table_name = model_name.to_s.demodulize.underscore pluralize_table_names ? table_name.pluralize : table_name end