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Diffstat (limited to 'activerecord/lib/active_record/validations/uniqueness.rb')
| -rw-r--r-- | activerecord/lib/active_record/validations/uniqueness.rb | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb new file mode 100644 index 0000000000..5a1dbc8e53 --- /dev/null +++ b/activerecord/lib/active_record/validations/uniqueness.rb @@ -0,0 +1,238 @@ +# frozen_string_literal: true + +module ActiveRecord + module Validations + class UniquenessValidator < ActiveModel::EachValidator # :nodoc: + def initialize(options) + if options[:conditions] && !options[:conditions].respond_to?(:call) + raise ArgumentError, "#{options[:conditions]} was passed as :conditions but is not callable. " \ + "Pass a callable instead: `conditions: -> { where(approved: true) }`" + end + unless Array(options[:scope]).all? { |scope| scope.respond_to?(:to_sym) } + raise ArgumentError, "#{options[:scope]} is not supported format for :scope option. " \ + "Pass a symbol or an array of symbols instead: `scope: :user_id`" + end + super({ case_sensitive: true }.merge!(options)) + @klass = options[:class] + end + + def validate_each(record, attribute, value) + finder_class = find_finder_class_for(record) + value = map_enum_attribute(finder_class, attribute, value) + + relation = build_relation(finder_class, attribute, value) + if record.persisted? + if finder_class.primary_key + relation = relation.where.not(finder_class.primary_key => record.id_in_database) + else + raise UnknownPrimaryKey.new(finder_class, "Can not validate uniqueness for persisted record without primary key.") + end + end + relation = scope_relation(record, relation) + relation = relation.merge(options[:conditions]) if options[:conditions] + + if relation.exists? + error_options = options.except(:case_sensitive, :scope, :conditions) + error_options[:value] = value + + record.errors.add(attribute, :taken, error_options) + end + end + + private + # The check for an existing value should be run from a class that + # isn't abstract. This means working down from the current class + # (self), to the first non-abstract class. Since classes don't know + # their subclasses, we have to build the hierarchy between self and + # the record's class. + def find_finder_class_for(record) + class_hierarchy = [record.class] + + while class_hierarchy.first != @klass + class_hierarchy.unshift(class_hierarchy.first.superclass) + end + + class_hierarchy.detect { |klass| !klass.abstract_class? } + end + + def build_relation(klass, attribute, value) + if reflection = klass._reflect_on_association(attribute) + attribute = reflection.foreign_key + value = value.attributes[reflection.klass.primary_key] unless value.nil? + end + + if value.nil? + return klass.unscoped.where!(attribute => value) + end + + # the attribute may be an aliased attribute + if klass.attribute_alias?(attribute) + attribute = klass.attribute_alias(attribute) + end + + attribute_name = attribute.to_s + value = klass.predicate_builder.build_bind_attribute(attribute_name, value) + + table = klass.arel_table + column = klass.columns_hash[attribute_name] + + comparison = if !options[:case_sensitive] + # will use SQL LOWER function before comparison, unless it detects a case insensitive collation + klass.connection.case_insensitive_comparison(table, attribute, column, value) + else + klass.connection.case_sensitive_comparison(table, attribute, column, value) + end + klass.unscoped.where!(comparison) + end + + def scope_relation(record, relation) + Array(options[:scope]).each do |scope_item| + scope_value = if record.class._reflect_on_association(scope_item) + record.association(scope_item).reader + else + record._read_attribute(scope_item) + end + relation = relation.where(scope_item => scope_value) + end + + relation + end + + def map_enum_attribute(klass, attribute, value) + mapping = klass.defined_enums[attribute.to_s] + value = mapping[value] if value && mapping + value + end + end + + module ClassMethods + # Validates whether the value of the specified attributes are unique + # across the system. Useful for making sure that only one user + # can be named "davidhh". + # + # class Person < ActiveRecord::Base + # validates_uniqueness_of :user_name + # end + # + # It can also validate whether the value of the specified attributes are + # unique based on a <tt>:scope</tt> parameter: + # + # class Person < ActiveRecord::Base + # validates_uniqueness_of :user_name, scope: :account_id + # end + # + # Or even multiple scope parameters. For example, making sure that a + # teacher can only be on the schedule once per semester for a particular + # class. + # + # class TeacherSchedule < ActiveRecord::Base + # validates_uniqueness_of :teacher_id, scope: [:semester_id, :class_id] + # end + # + # It is also possible to limit the uniqueness constraint to a set of + # records matching certain conditions. In this example archived articles + # are not being taken into consideration when validating uniqueness + # of the title attribute: + # + # class Article < ActiveRecord::Base + # validates_uniqueness_of :title, conditions: -> { where.not(status: 'archived') } + # end + # + # When the record is created, a check is performed to make sure that no + # record exists in the database with the given value for the specified + # attribute (that maps to a column). When the record is updated, + # the same check is made but disregarding the record itself. + # + # Configuration options: + # + # * <tt>:message</tt> - Specifies a custom error message (default is: + # "has already been taken"). + # * <tt>:scope</tt> - One or more columns by which to limit the scope of + # the uniqueness constraint. + # * <tt>:conditions</tt> - Specify the conditions to be included as a + # <tt>WHERE</tt> SQL fragment to limit the uniqueness constraint lookup + # (e.g. <tt>conditions: -> { where(status: 'active') }</tt>). + # * <tt>:case_sensitive</tt> - Looks for an exact match. Ignored by + # non-text columns (+true+ by default). + # * <tt>:allow_nil</tt> - If set to +true+, skips this validation if the + # attribute is +nil+ (default is +false+). + # * <tt>:allow_blank</tt> - If set to +true+, skips this validation if the + # attribute is blank (default is +false+). + # * <tt>:if</tt> - Specifies a method, proc or string to call to determine + # if the validation should occur (e.g. <tt>if: :allow_validation</tt>, + # or <tt>if: Proc.new { |user| user.signup_step > 2 }</tt>). The method, + # proc or string should return or evaluate to a +true+ or +false+ value. + # * <tt>:unless</tt> - Specifies a method, proc or string to call to + # determine if the validation should not occur (e.g. <tt>unless: :skip_validation</tt>, + # or <tt>unless: Proc.new { |user| user.signup_step <= 2 }</tt>). The + # method, proc or string should return or evaluate to a +true+ or +false+ + # value. + # + # === Concurrency and integrity + # + # Using this validation method in conjunction with + # {ActiveRecord::Base#save}[rdoc-ref:Persistence#save] + # does not guarantee the absence of duplicate record insertions, because + # uniqueness checks on the application level are inherently prone to race + # conditions. For example, suppose that two users try to post a Comment at + # the same time, and a Comment's title must be unique. At the database-level, + # the actions performed by these users could be interleaved in the following manner: + # + # User 1 | User 2 + # ------------------------------------+-------------------------------------- + # # User 1 checks whether there's | + # # already a comment with the title | + # # 'My Post'. This is not the case. | + # SELECT * FROM comments | + # WHERE title = 'My Post' | + # | + # | # User 2 does the same thing and also + # | # infers that their title is unique. + # | SELECT * FROM comments + # | WHERE title = 'My Post' + # | + # # User 1 inserts their comment. | + # INSERT INTO comments | + # (title, content) VALUES | + # ('My Post', 'hi!') | + # | + # | # User 2 does the same thing. + # | INSERT INTO comments + # | (title, content) VALUES + # | ('My Post', 'hello!') + # | + # | # ^^^^^^ + # | # Boom! We now have a duplicate + # | # title! + # + # The best way to work around this problem is to add a unique index to the database table using + # {connection.add_index}[rdoc-ref:ConnectionAdapters::SchemaStatements#add_index]. + # In the rare case that a race condition occurs, the database will guarantee + # the field's uniqueness. + # + # When the database catches such a duplicate insertion, + # {ActiveRecord::Base#save}[rdoc-ref:Persistence#save] will raise an ActiveRecord::StatementInvalid + # exception. You can either choose to let this error propagate (which + # will result in the default Rails exception page being shown), or you + # can catch it and restart the transaction (e.g. by telling the user + # that the title already exists, and asking them to re-enter the title). + # This technique is also known as + # {optimistic concurrency control}[https://en.wikipedia.org/wiki/Optimistic_concurrency_control]. + # + # The bundled ActiveRecord::ConnectionAdapters distinguish unique index + # constraint errors from other types of database errors by throwing an + # ActiveRecord::RecordNotUnique exception. For other adapters you will + # have to parse the (database-specific) exception message to detect such + # a case. + # + # The following bundled adapters throw the ActiveRecord::RecordNotUnique exception: + # + # * ActiveRecord::ConnectionAdapters::Mysql2Adapter. + # * ActiveRecord::ConnectionAdapters::SQLite3Adapter. + # * ActiveRecord::ConnectionAdapters::PostgreSQLAdapter. + def validates_uniqueness_of(*attr_names) + validates_with UniquenessValidator, _merge_attributes(attr_names) + end + end + end +end |