Fix finalize_column_type_change to not recreate already existing in…

…dexes on the temporary column

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## master (unreleased)
 
+- Fix `finalize_column_type_change` to not recreate already existing indexes on the temporary column
 - Remove potentially heavy queries used to get the ranges of a background migration
 
 ## 0.12.0 (2024-01-18)

lib/online_migrations/change_column_type_helpers.rb

@@ -416,15 +416,8 @@ def __copy_indexes(table_name, from_column, to_column)
               end
             end
 
-          if index.name.include?(from_column)
-            name = index.name.gsub(from_column, to_column)
-          end
-
-          name = index_name(table_name, new_columns) if !name || name.length > max_identifier_length
-
           options = {
             unique: index.unique,
-            name: name,
             length: index.lengths,
             order: index.orders,
           }

lib/online_migrations/schema_statements.rb

@@ -681,32 +681,26 @@ def add_reference_concurrently(table_name, ref_name, **options)
     # @see https://edgeapi.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_index
     #
     def add_index(table_name, column_name, **options)
-      algorithm = options[:algorithm]
-
-      __ensure_not_in_transaction! if algorithm == :concurrently
-
-      column_names = index_column_names(column_name || options[:column])
-
-      index_name = options[:name]
-      index_name ||= index_name(table_name, column_names)
+      __ensure_not_in_transaction! if options[:algorithm] == :concurrently
 
-      if index_exists?(table_name, column_name, **options)
+      index = indexes(table_name).find { |i| i.defined_for?(column_name, **options) }
+      if index
         schema = __schema_for_table(table_name)
 
-        if __index_valid?(index_name, schema: schema)
+        if __index_valid?(index.name, schema: schema)
           Utils.say("Index was not created because it already exists.")
           return
         else
           Utils.say("Recreating invalid index: table_name: #{table_name}, column_name: #{column_name}")
-          remove_index(table_name, column_name, name: index_name, algorithm: algorithm)
+          remove_index(table_name, column_name, **options)
         end
       end
 
       if OnlineMigrations.config.statement_timeout
         # "CREATE INDEX CONCURRENTLY" requires a "SHARE UPDATE EXCLUSIVE" lock.
         # It only conflicts with constraint validations, creating/removing indexes,
         # and some other "ALTER TABLE"s.
-        super(table_name, column_name, **options.merge(name: index_name))
+        super
       else
         OnlineMigrations.deprecator.warn(<<~MSG)
           Running `add_index` without a statement timeout is deprecated.
@@ -716,7 +710,7 @@ def add_index(table_name, column_name, **options)
         MSG
 
         disable_statement_timeout do
-          super(table_name, column_name, **options.merge(name: index_name))
+          super
         end
       end
     end

test/schema_statements/changing_column_type_test.rb

@@ -351,6 +351,21 @@ def test_finalize_column_type_change_keeps_columns_in_sync
       assert_equal project.id, old_id
     end
 
+    def test_finalize_column_type_change_does_not_recreate_existing_index
+      # assert_not @connection.index_exists?(:projects, :company_id)
+      @connection.add_index(:projects, :company_id)
+
+      @connection.initialize_column_type_change(:projects, :company_id, :bigint)
+      # Lets imagine, that the index was added before, manually, to the column.
+      @connection.add_index(:projects, :company_id_for_type_change, name: "my_custom_name") # use custom index name
+
+      refute_sql("CREATE INDEX") do
+        @connection.finalize_column_type_change(:projects, :company_id)
+        assert @connection.index_exists?(:projects, :company_id)
+        assert @connection.index_exists?(:projects, :company_id_for_type_change)
+      end
+    end
+
     def test_finalize_columns_type_change
       @connection.initialize_columns_type_change(:projects, [[:id, :bigint], [:name, :string]])
       @connection.finalize_columns_type_change(:projects, :id, :name)