Methods
- column_defaults
- column_for_attribute
- column_names
- columns
- content_columns
- ignored_columns
- ignored_columns=
- initialize_load_schema_monitor
- next_sequence_value
- prefetch_primary_key?
- protected_environments
- protected_environments=
- quoted_table_name
- reload_schema_from_cache
- reset_column_information
- sequence_name
- sequence_name=
- table_exists?
- table_name
- table_name=
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.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 474
def column_defaults
load_schema
@column_defaults ||= _default_attributes.deep_dup.to_hash.freeze
end
π 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>, ...>
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 465
def column_for_attribute(name)
name = name.to_s
columns_hash.fetch(name) do
ConnectionAdapters::NullColumn.new(name)
end
end
π See on GitHub
column_names()
Returns an array of column names as strings.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 480
def column_names
@column_names ||= columns.map(&:name).freeze
end
π See on GitHub
columns()
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 433
def columns
load_schema unless @columns
@columns ||= columns_hash.values.freeze
end
π See on GitHub
content_columns()
Returns an array of column objects where the primary id, all columns ending in β_idβ or β_countβ, and columns used for single table inheritance have been removed.
π Source code
# File activerecord/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
π See on GitHub
ignored_columns()
The list of columns names the model should ignore. Ignored columns wonβt have attribute accessors defined, and wonβt be referenced in SQL queries.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 332
def ignored_columns
@ignored_columns || superclass.ignored_columns
end
π See on GitHub
ignored_columns=(columns)
Sets the columns names the model should ignore. Ignored columns wonβt have attribute accessors defined, and wonβt 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 βcategoryβ 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 βcategoryβ, 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
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 367
def ignored_columns=(columns)
reload_schema_from_cache
@ignored_columns = columns.map(&:to_s).freeze
end
π See on GitHub
next_sequence_value()
Returns the next value that will be used as the primary key on an insert statement.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 412
def next_sequence_value
with_connection { |c| c.next_sequence_value(sequence_name) }
end
π See on GitHub
prefetch_primary_key?()
Determines if the primary key values should be selected from their corresponding sequence before the insert statement.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 406
def prefetch_primary_key?
with_connection { |c| c.prefetch_primary_key?(table_name) }
end
π See on GitHub
protected_environments()
The array of names of environments where destructive actions should be prohibited. By default, the value is ["production"]
.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 313
def protected_environments
if defined?(@protected_environments)
@protected_environments
else
superclass.protected_environments
end
end
π See on GitHub
protected_environments=(environments)
Sets an array of names of environments where destructive actions should be prohibited.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 322
def protected_environments=(environments)
@protected_environments = environments.map(&:to_s)
end
π See on GitHub
quoted_table_name()
Returns a quoted version of the table name, used to construct SQL statements.
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 286
def quoted_table_name
@quoted_table_name ||= adapter_class.quote_table_name(table_name)
end
π 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[7.2]
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
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 525
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
π See on GitHub
sequence_name()
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 372
def sequence_name
if base_class?
@sequence_name ||= reset_sequence_name
else
(@sequence_name ||= nil) || base_class.sequence_name
end
end
π 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
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 399
def sequence_name=(value)
@sequence_name = value.to_s
@explicit_sequence_name = true
end
π See on GitHub
table_exists?()
Indicates whether the table associated with this class exists
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 417
def table_exists?
schema_cache.data_source_exists?(table_name)
end
π 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 parentβs 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 βmyapp_β as a prefix, the table name guess for an Invoice class becomes βmyapp_invoicesβ. Invoice::Lineitem becomes βmyapp_invoice_lineitemsβ.
Active Model Namingβs 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
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 260
def table_name
reset_table_name unless defined?(@table_name)
@table_name
end
π See on GitHub
table_name=(value)
Sets the table name explicitly. Example:
class Project < ActiveRecord::Base
self.table_name = "project"
end
π Source code
# File activerecord/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
@quoted_table_name = nil
@arel_table = nil
@sequence_name = nil unless @explicit_sequence_name
@predicate_builder = nil
end
π See on GitHub
Instance Protected methods
initialize_load_schema_monitor()
π Source code
# File activerecord/lib/active_record/model_schema.rb, line 549
def initialize_load_schema_monitor
@load_schema_monitor = Monitor.new
end
π See on GitHub
reload_schema_from_cache(recursive = true)
π Source code
# File activerecord/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
π See on GitHub