Merge pull request #49178 from ccutrer/add_check_constraint_if_not_exists

Adds support for `if_not_exists` when adding a check constraint.

activerecord/CHANGELOG.md

@@ -1,3 +1,11 @@
+*   Adds support for `if_not_exists` when adding a check constraint.
+
+    ```ruby
+    add_check_constraint :posts, "post_type IN ('blog', 'comment', 'share')", if_not_exists: true
+    ```
+
+    *Cody Cutrer*
+
 *   Raise an `ArgumentError` when `#accepts_nested_attributes_for` is declared more than once for an association in
     the same class. Previously, the last declaration would silently override the previous one. Overriding in a subclass
     is still allowed.

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

@@ -1225,12 +1225,16 @@ module ActiveRecord
       # The +options+ hash can include the following keys:
       # [<tt>:name</tt>]
       #   The constraint name. Defaults to <tt>chk_rails_<identifier></tt>.
+      # [<tt>:if_not_exists</tt>]
+      #   Silently ignore if the constraint already exists, rather than raise an error.
       # [<tt>:validate</tt>]
       #   (PostgreSQL only) Specify whether or not the constraint should be validated. Defaults to +true+.
-      def add_check_constraint(table_name, expression, **options)
+      def add_check_constraint(table_name, expression, if_not_exists: false, **options)
         return unless supports_check_constraints?
 
         options = check_constraint_options(table_name, expression, options)
+        return if if_not_exists && check_constraint_exists?(table_name, **options)
+
         at = create_alter_table(table_name)
         at.add_check_constraint(expression, options)
 

activerecord/lib/active_record/migration/command_recorder.rb

@@ -308,12 +308,19 @@ module ActiveRecord
         end
 
         def invert_add_check_constraint(args)
-          args.last.delete(:validate) if args.last.is_a?(Hash)
+          if (options = args.last).is_a?(Hash)
+            options.delete(:validate)
+            options[:if_exists] = options.delete(:if_not_exists) if options.key?(:if_not_exists)
+          end
           super
         end
 
         def invert_remove_check_constraint(args)
           raise ActiveRecord::IrreversibleMigration, "remove_check_constraint is only reversible if given an expression." if args.size < 2
+
+          if (options = args.last).is_a?(Hash)
+            options[:if_not_exists] = options.delete(:if_exists) if options.key?(:if_exists)
+          end
           super
         end
 

activerecord/test/cases/migration/check_constraint_test.rb

@@ -123,6 +123,14 @@ if ActiveRecord::Base.connection.supports_check_constraints?
           end
         end
 
+        def test_add_check_constraint_with_if_not_exists_options
+          @connection.add_check_constraint :trades, "quantity > 0"
+
+          assert_nothing_raised do
+            @connection.add_check_constraint :trades, "quantity > 0", if_not_exists: true
+          end
+        end
+
         if supports_non_unique_constraint_name?
           def test_add_constraint_with_same_name_to_different_table
             @connection.add_check_constraint :trades, "quantity > 0", name: "greater_than_zero"

activerecord/test/cases/migration/command_recorder_test.rb

@@ -460,6 +460,16 @@ module ActiveRecord
         end
       end
 
+      def test_invert_add_check_constraint
+        enable = @recorder.inverse_of :add_check_constraint, [:dogs, "speed > 0", name: "speed_check"]
+        assert_equal [:remove_check_constraint, [:dogs, "speed > 0", name: "speed_check"], nil], enable
+      end
+
+      def test_invert_add_check_constraint_if_not_exists
+        enable = @recorder.inverse_of :add_check_constraint, [:dogs, "speed > 0", name: "speed_check", if_not_exists: true]
+        assert_equal [:remove_check_constraint, [:dogs, "speed > 0", name: "speed_check", if_exists: true], nil], enable
+      end
+
       def test_invert_remove_check_constraint
         enable = @recorder.inverse_of :remove_check_constraint, [:dogs, "speed > 0", name: "speed_check"]
         assert_equal [:add_check_constraint, [:dogs, "speed > 0", name: "speed_check"], nil], enable
@@ -471,6 +481,11 @@ module ActiveRecord
         end
       end
 
+      def test_invert_remove_check_constraint_if_exists
+        enable = @recorder.inverse_of :remove_check_constraint, [:dogs, "speed > 0", name: "speed_check", if_exists: true]
+        assert_equal [:add_check_constraint, [:dogs, "speed > 0", name: "speed_check", if_not_exists: true], nil], enable
+      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"]