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 472 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 463 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 478 def column_names @column_names ||= columns.map(&:name).freeze end
# File lib/active_record/model_schema.rb, line 432 def columns @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 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
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 331 def ignored_columns @ignored_columns || superclass.ignored_columns 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 366 def ignored_columns=(columns) reload_schema_from_cache @ignored_columns = columns.map(&:to_s).freeze end
Load the model’s schema information either from the schema cache or directly from the database.
# File 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
Returns the next value that will be used as the primary key on an insert statement.
# File lib/active_record/model_schema.rb, line 411 def next_sequence_value with_connection { |c| c.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 405 def prefetch_primary_key? with_connection { |c| c.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 312 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 321 def protected_environments=(environments) @protected_environments = environments.map(&:to_s) end
Returns a quoted version of the table name.
# File lib/active_record/model_schema.rb, line 285 def quoted_table_name adapter_class.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[8.0] 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 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
# File 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
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 398 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 416 def table_exists? 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 260 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 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
Protected Instance Methods
# File lib/active_record/model_schema.rb, line 549 def initialize_load_schema_monitor @load_schema_monitor = Monitor.new end
# File 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
Private Instance Methods
Computes and returns a table name according to default conventions.
# File 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
# File 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
# File 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
# File lib/active_record/model_schema.rb, line 583 def schema_loaded? @schema_loaded end
# File 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
Guesses the table name, but does not decorate it with prefix and suffix information.
# File 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