Merge pull request rails#47971 from alpaca-tc/add_support_using_keyword_for_unique_constraint

Adds support `USING INDEX` for unique constraints in PostgreSQL.

Author: yahonda

activerecord/CHANGELOG.md

@@ -228,11 +228,12 @@
     add_unique_key :items, [:position], deferrable: :deferred
     ```
 
-    PostgreSQL allows users to create a unique constraints on top of the unique
-    index that cannot be deferred. In this case, even if users creates deferrable
-    unique constraint, the existing unique index does not allow users to violate uniqueness
-    within the transaction. If you want to change existing unique index to deferrable,
-    you need execute `remove_index` before creating deferrable unique constraints.
+    If you want to change an existing unique index to deferrable, you can use :using_index
+    to create deferrable unique constraints.
+
+    ```ruby
+    add_unique_key :items, deferrable: :deferred, using_index: "index_items_on_position"
+    ```
 
     *Hiroyuki Ishii*
 

activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb

@@ -53,7 +53,12 @@ def visit_UniqueKeyDefinition(o)
             sql = ["CONSTRAINT"]
             sql << quote_column_name(o.name)
             sql << "UNIQUE"
-            sql << "(#{column_name})"
+
+            if o.using_index
+              sql << "USING INDEX #{quote_column_name(o.using_index)}"
+            else
+              sql << "(#{column_name})"
+            end
 
             if o.deferrable
               sql << "DEFERRABLE INITIALLY #{o.deferrable.to_s.upcase}"

activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb

@@ -220,6 +220,10 @@ def deferrable
           options[:deferrable]
         end
 
+        def using_index
+          options[:using_index]
+        end
+
         def export_name_on_schema_dump?
           !ActiveRecord::SchemaDumper.unique_ignore_pattern.match?(name) if name
         end

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -700,24 +700,24 @@ def remove_exclusion_constraint(table_name, expression = nil, **options)
 
         # Adds a new unique constraint to the table.
         #
-        # PostgreSQL allows users to create a unique constraints on top of the unique index
-        # that cannot be deferred. In this case, even if users creates deferrable unique constraint,
-        # the existing unique index does not allow users to violate uniqueness within the transaction.
-        # If you want to change existing unique index to deferrable, you need execute `remove_index`
-        # before creating deferrable unique constraints.
-        #
         #   add_unique_key :sections, [:position], deferrable: :deferred, name: "unique_position"
         #
         # generates:
         #
         #   ALTER TABLE "sections" ADD CONSTRAINT unique_position UNIQUE (position) DEFERRABLE INITIALLY DEFERRED
         #
+        # If you want to change an existing unique index to deferrable, you can use :using_index to create deferrable unique constraints.
+        #
+        #   add_unique_key :sections, deferrable: :deferred, name: "unique_position", using_index: "index_sections_on_position"
+        #
         # The +options+ hash can include the following keys:
         # [<tt>:name</tt>]
         #   The constraint name. Defaults to <tt>uniq_rails_<identifier></tt>.
         # [<tt>:deferrable</tt>]
         #   Specify whether or not the unique constraint should be deferrable. Valid values are +false+ or +:immediate+ or +:deferred+ to specify the default behavior. Defaults to +false+.
-        def add_unique_key(table_name, column_name, **options)
+        # [<tt>:using_index</tt>]
+        #   To specify an existing unique index name. Defaults to +nil+.
+        def add_unique_key(table_name, column_name = nil, **options)
           options = unique_key_options(table_name, column_name, options)
           at = create_alter_table(table_name)
           at.add_unique_key(column_name, options)
@@ -728,6 +728,10 @@ def add_unique_key(table_name, column_name, **options)
         def unique_key_options(table_name, column_name, options) # :nodoc:
           assert_valid_deferrable(options[:deferrable])
 
+          if column_name && options[:using_index]
+            raise ArgumentError, "Cannot specify both column_name and :using_index options."
+          end
+
           options = options.dup
           options[:name] ||= unique_key_name(table_name, column_name: column_name, **options)
           options
@@ -1016,8 +1020,8 @@ def exclusion_constraint_for!(table_name, expression: nil, **options)
 
           def unique_key_name(table_name, **options)
             options.fetch(:name) do
-              column_name = options.fetch(:column_name)
-              identifier = "#{table_name}_#{column_name}_unique"
+              column_name_or_index_name = options.fetch(:column_name) || options[:using_index]
+              identifier = "#{table_name}_#{column_name_or_index_name}_unique"
               hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
 
               "uniq_rails_#{hashed_identifier}"

activerecord/lib/active_record/migration/command_recorder.rb

@@ -318,6 +318,13 @@ def invert_remove_exclusion_constraint(args)
           super
         end
 
+        def invert_add_unique_key(args)
+          options = args.dup.extract_options!
+
+          raise ActiveRecord::IrreversibleMigration, "add_unique_key is not reversible if given an using_index." if options[:using_index]
+          super
+        end
+
         def invert_remove_unique_key(args)
           _table, columns = args.dup.tap(&:extract_options!)
 

activerecord/test/cases/migration/command_recorder_test.rb

@@ -471,6 +471,12 @@ def test_invert_remove_check_constraint_without_expression
         end
       end
 
+      def test_invert_add_unique_key_constraint_with_using_index
+        assert_raises(ActiveRecord::IrreversibleMigration) do
+          @recorder.inverse_of :add_unique_key, [:dogs, using_index: "unique_index"]
+        end
+      end
+
       def test_invert_remove_unique_key_constraint
         enable = @recorder.inverse_of :remove_unique_key, [:dogs, ["speed"], deferrable: :deferred, name: "uniq_speed"]
         assert_equal [:add_unique_key, [:dogs, ["speed"], deferrable: :deferred, name: "uniq_speed"], nil], enable

activerecord/test/cases/migration/unique_key_test.rb

@@ -147,6 +147,42 @@ def test_added_deferrable_initially_immediate_unique_key
           end
         end
 
+        def test_add_unique_key_with_name_and_using_index
+          @connection.add_index :sections, [:position], name: "unique_index", unique: true
+          @connection.add_unique_key :sections, name: "unique_constraint", deferrable: :immediate, using_index: "unique_index"
+
+          unique_keys = @connection.unique_keys("sections")
+          assert_equal 1, unique_keys.size
+
+          constraint = unique_keys.first
+          assert_equal "sections", constraint.table_name
+          assert_equal "unique_constraint", constraint.name
+          assert_equal ["position"], constraint.columns
+          assert_equal :immediate, constraint.deferrable
+        end
+
+        def test_add_unique_key_with_only_using_index
+          @connection.add_index :sections, [:position], name: "unique_index", unique: true
+          @connection.add_unique_key :sections, using_index: "unique_index"
+
+          unique_keys = @connection.unique_keys("sections")
+          assert_equal 1, unique_keys.size
+
+          constraint = unique_keys.first
+          assert_equal "sections", constraint.table_name
+          assert_equal "uniq_rails_79b901ffb4", constraint.name
+          assert_equal ["position"], constraint.columns
+          assert_equal false, constraint.deferrable
+        end
+
+        def test_add_unique_key_with_columns_and_using_index
+          @connection.add_index :sections, [:position], name: "unique_index", unique: true
+
+          assert_raises(ArgumentError) do
+            @connection.add_unique_key :sections, [:position], using_index: "unique_index"
+          end
+        end
+
         def test_remove_unique_key
           assert_equal 0, @connection.unique_keys("sections").size