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module ActiveRecord
module ModelSchema
extend ActiveSupport::Concern
included do
##
# :singleton-method:
# Accessor for the prefix type that will be prepended to every primary key column name.
# The options are :table_name and :table_name_with_underscore. If the first is specified,
# the Product class will look for "productid" instead of "id" as the primary column. If the
# latter is specified, the Product class will look for "product_id" instead of "id". Remember
# that this is a global setting for all Active Records.
mattr_accessor :primary_key_prefix_type, instance_writer: false
##
# :singleton-method:
# Accessor for the name of the prefix string to prepend to every table name. So if set
# to "basecamp_", all table names will be named like "basecamp_projects", "basecamp_people",
# etc. This is a convenient way of creating a namespace for tables in a shared database.
# By default, the prefix is the empty string.
#
# If you are organising your models within modules you can add a prefix to the models within
# a namespace by defining a singleton method in the parent module called table_name_prefix which
# returns your chosen prefix.
class_attribute :table_name_prefix, instance_writer: false
self.table_name_prefix = ""
##
# :singleton-method:
# Works like +table_name_prefix+, but appends instead of prepends (set to "_basecamp" gives "projects_basecamp",
# "people_basecamp"). By default, the suffix is the empty string.
#
# If you are organising your models within modules, you can add a suffix to the models within
# a namespace by defining a singleton method in the parent module called table_name_suffix which
# returns your chosen suffix.
class_attribute :table_name_suffix, instance_writer: false
self.table_name_suffix = ""
##
# :singleton-method:
# Accessor for the name of the schema migrations table. By default, the value is "schema_migrations"
class_attribute :schema_migrations_table_name, instance_accessor: false
self.schema_migrations_table_name = "schema_migrations"
##
# :singleton-method:
# Accessor for the name of the internal metadata table. By default, the value is "ar_internal_metadata"
class_attribute :internal_metadata_table_name, instance_accessor: false
self.internal_metadata_table_name = "ar_internal_metadata"
##
# :singleton-method:
# Accessor for an array of names of environments where destructive actions should be prohibited. By default,
# the value is ["production"]
class_attribute :protected_environments, instance_accessor: false
self.protected_environments = ["production"]
##
# :singleton-method:
# Indicates whether table names should be the pluralized versions of the corresponding class names.
# If true, the default table name for a Product class will be +products+. If false, it would just be +product+.
# See table_name for the full rules on table/class naming. This is true, by default.
class_attribute :pluralize_table_names, instance_writer: false
self.pluralize_table_names = true
##
# :singleton-method:
# Accessor for 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.
class_attribute :ignored_columns, instance_accessor: false
self.ignored_columns = [].freeze
self.inheritance_column = "type"
delegate :type_for_attribute, to: :class
end
# Derives the join table name for +first_table+ and +second_table+. The
# table names appear in alphabetical order. A common prefix is removed
# (useful for namespaced models like Music::Artist and Music::Record):
#
# artists, records => artists_records
# records, artists => artists_records
# music_artists, music_records => music_artists_records
def self.derive_join_table_name(first_table, second_table) # :nodoc:
[first_table.to_s, second_table.to_s].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').tr("\0", "_")
end
module ClassMethods
# 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
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
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 a quoted version of the table name, used to construct SQL statements.
def quoted_table_name
@quoted_table_name ||= connection.quote_table_name(table_name)
end
# Computes the table name, (re)sets it internally, and returns it.
def reset_table_name #:nodoc:
self.table_name = if abstract_class?
superclass == Base ? nil : superclass.table_name
elsif superclass.abstract_class?
superclass.table_name || compute_table_name
else
compute_table_name
end
end
def full_table_name_prefix #:nodoc:
(parents.detect { |p| p.respond_to?(:table_name_prefix) } || self).table_name_prefix
end
def full_table_name_suffix #:nodoc:
(parents.detect { |p| p.respond_to?(:table_name_suffix) } || self).table_name_suffix
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'
def inheritance_column
(@inheritance_column ||= nil) || superclass.inheritance_column
end
# Sets the value of inheritance_column
def inheritance_column=(value)
@inheritance_column = value.to_s
@explicit_inheritance_column = true
end
def sequence_name
if base_class == self
@sequence_name ||= reset_sequence_name
else
(@sequence_name ||= nil) || base_class.sequence_name
end
end
def reset_sequence_name #:nodoc:
@explicit_sequence_name = false
@sequence_name = connection.default_sequence_name(table_name, primary_key)
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
def sequence_name=(value)
@sequence_name = value.to_s
@explicit_sequence_name = true
end
# Determines if the primary key values should be selected from their
# corresponding sequence before the insert statement.
def prefetch_primary_key?
connection.prefetch_primary_key?(table_name)
end
# Returns the next value that will be used as the primary key on
# an insert statement.
def next_sequence_value
connection.next_sequence_value(sequence_name)
end
# Indicates whether the table associated with this class exists
def table_exists?
connection.schema_cache.data_source_exists?(table_name)
end
def attributes_builder # :nodoc:
@attributes_builder ||= AttributeSet::Builder.new(attribute_types, primary_key) do |name|
unless columns_hash.key?(name)
_default_attributes[name].dup
end
end
end
def columns_hash # :nodoc:
load_schema
@columns_hash
end
def columns
load_schema
@columns ||= columns_hash.values
end
def attribute_types # :nodoc:
load_schema
@attribute_types ||= Hash.new(Type.default_value)
end
def yaml_encoder # :nodoc:
@yaml_encoder ||= AttributeSet::YAMLEncoder.new(attribute_types)
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
def type_for_attribute(attr_name, &block)
if block
attribute_types.fetch(attr_name, &block)
else
attribute_types[attr_name]
end
end
# Returns a hash where the keys are column names and the values are
# default values when instantiating the Active Record object for this table.
def column_defaults
load_schema
_default_attributes.to_hash
end
def _default_attributes # :nodoc:
@default_attributes ||= AttributeSet.new({})
end
# Returns an array of column names as strings.
def column_names
@column_names ||= columns.map(&:name)
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.
def content_columns
@content_columns ||= columns.reject do |c|
c.name == primary_key ||
c.name == inheritance_column ||
c.name.end_with?("_id") ||
c.name.end_with?("_count")
end
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[5.0]
# 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
def reset_column_information
connection.clear_cache!
undefine_attribute_methods
connection.schema_cache.clear_data_source_cache!(table_name)
reload_schema_from_cache
end
private
def schema_loaded?
defined?(@columns_hash) && @columns_hash
end
def load_schema
unless schema_loaded?
load_schema!
end
end
def load_schema!
@columns_hash = connection.schema_cache.columns_hash(table_name).except(*ignored_columns)
@columns_hash.each do |name, column|
define_attribute(
name,
connection.lookup_cast_type_from_column(column),
default: column.default,
user_provided_default: false
)
end
end
def reload_schema_from_cache
@arel_engine = nil
@arel_table = nil
@column_names = nil
@attribute_types = nil
@content_columns = nil
@default_attributes = nil
@inheritance_column = nil unless defined?(@explicit_inheritance_column) && @explicit_inheritance_column
@attributes_builder = nil
@columns = nil
@columns_hash = nil
@attribute_names = nil
@yaml_encoder = nil
direct_descendants.each do |descendant|
descendant.send(:reload_schema_from_cache)
end
end
# Guesses the table name, but does not decorate it with prefix and suffix information.
def undecorated_table_name(class_name = base_class.name)
table_name = class_name.to_s.demodulize.underscore
pluralize_table_names ? table_name.pluralize : table_name
end
# Computes and returns a table name according to default conventions.
def compute_table_name
base = base_class
if self == base
# Nested classes are prefixed with singular parent table name.
if parent < Base && !parent.abstract_class?
contained = parent.table_name
contained = contained.singularize if parent.pluralize_table_names
contained += "_"
end
"#{full_table_name_prefix}#{contained}#{undecorated_table_name(name)}#{full_table_name_suffix}"
else
# STI subclasses always use their superclass' table.
base.table_name
end
end
end
end
end