aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/validations/uniqueness.rb
blob: ee080451a924c1826f8030a748a21fd747e452bb (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
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
        super({ case_sensitive: true }.merge!(options))
        @klass = options[:class]
      end

      def validate_each(record, attribute, value)
        finder_class = find_finder_class_for(record)
        table = finder_class.arel_table
        value = map_enum_attribute(finder_class, attribute, value)
        value = deserialize_attribute(record, attribute, value)

        relation = build_relation(finder_class, table, attribute, value)
        relation = relation.and(table[finder_class.primary_key.to_sym].not_eq(record.id)) if record.persisted?
        relation = scope_relation(record, table, relation)
        relation = finder_class.unscoped.where(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

    protected
      # 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) #:nodoc:
        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, table, attribute, value) #:nodoc:
        if reflection = klass.reflect_on_association(attribute)
          attribute = reflection.foreign_key
          value = value.attributes[reflection.primary_key_column.name] unless value.nil?
        end

        attribute_name = attribute.to_s

        # the attribute may be an aliased attribute
        if klass.attribute_aliases[attribute_name]
          attribute = klass.attribute_aliases[attribute_name]
          attribute_name = attribute.to_s
        end

        column = klass.columns_hash[attribute_name]
        value  = klass.connection.type_cast(value, column)
        value  = value.to_s[0, column.limit] if value && column.limit && column.text?

        if !options[:case_sensitive] && value && column.text?
          # 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
      end

      def scope_relation(record, table, relation)
        Array(options[:scope]).each do |scope_item|
          if reflection = record.class.reflect_on_association(scope_item)
            scope_value = record.send(reflection.foreign_key)
            scope_item  = reflection.foreign_key
          else
            scope_value = record.read_attribute(scope_item)
          end
          relation = relation.and(table[scope_item].eq(scope_value))
        end

        relation
      end

      def deserialize_attribute(record, attribute, value)
        coder = record.class.serialized_attributes[attribute.to_s]
        value = coder.dump value if value && coder
        value
      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 ot 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
      # 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!
      #
      # This could even happen if you use transactions with the 'serializable'
      # isolation level. The best way to work around this problem is to add a unique
      # index to the database table using
      # ActiveRecord::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 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}[http://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::MysqlAdapter.
      # * 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