Fix copying indexes with long names when changing column type

Fixes #44.

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## master (unreleased)
 
+- Fix copying indexes with long names when changing column type
 - Enhance error messages with the link to the detailed description
 
 ## 0.9.2 (2023-11-02)

lib/online_migrations/change_column_type_helpers.rb

@@ -423,6 +423,10 @@ def __copy_indexes(table_name, from_column, to_column)
 
           name = index.name.gsub(from_column, to_column)
 
+          # Generate a shorter name if needed.
+          max_identifier_length = 63 # could use just `max_identifier_length` method for ActiveRecord >= 5.0.
+          name = index_name(table_name, new_columns) if name.length > max_identifier_length
+
           options = {
             unique: index.unique,
             name: name,

lib/online_migrations/command_checker.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "erb"
-require "openssl"
 require "set"
 
 module OnlineMigrations
@@ -616,30 +615,14 @@ def add_check_constraint(table_name, expression, **options)
       def add_unique_constraint(table_name, column_name = nil, **options)
         return if new_or_small_table?(table_name) || options[:using_index] || !column_name
 
-        index_name = index_name(table_name, column_name)
+        index_name = Utils.index_name(table_name, column_name)
 
         raise_error :add_unique_constraint,
           add_index_code: command_str(:add_index, table_name, column_name, unique: true, name: index_name, algorithm: :concurrently),
           add_code: command_str(:add_unique_constraint, table_name, **options.merge(using_index: index_name)),
           remove_code: command_str(:remove_unique_constraint, table_name, column_name)
       end
 
-      # Implementation is from Active Record
-      def index_name(table_name, column_name)
-        max_index_name_size = 62
-        name = "index_#{table_name}_on_#{Array(column_name) * '_and_'}"
-        return name if name.bytesize <= max_index_name_size
-
-        # Fallback to short version, add hash to ensure uniqueness
-        hashed_identifier = "_#{OpenSSL::Digest::SHA256.hexdigest(name).first(10)}"
-        name = "idx_on_#{Array(column_name) * '_'}"
-
-        short_limit = max_index_name_size - hashed_identifier.bytesize
-        short_name = name[0, short_limit]
-
-        "#{short_name}#{hashed_identifier}"
-      end
-
       def validate_constraint(*)
         if crud_blocked?
           raise_error :validate_constraint

lib/online_migrations/schema_statements.rb

@@ -777,6 +777,22 @@ def remove_index(table_name, column_name = nil, **options)
       end
     end
 
+    # @private
+    # From ActiveRecord. Will not be needed for ActiveRecord >= 7.1.
+    def index_name(table_name, options)
+      if options.is_a?(Hash)
+        if options[:column]
+          Utils.index_name(table_name, options[:column])
+        elsif options[:name]
+          options[:name]
+        else
+          raise ArgumentError, "You must specify the index name"
+        end
+      else
+        index_name(table_name, column: options)
+      end
+    end
+
     # Extends default method to be idempotent and accept `:validate` option for Active Record < 5.2.
     #
     # @see https://edgeapi.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_foreign_key

lib/online_migrations/utils.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "openssl"
+
 module OnlineMigrations
   # @private
   module Utils
@@ -78,6 +80,23 @@ def foreign_table_name(ref_name, options)
         end
       end
 
+      # Implementation is from ActiveRecord.
+      # This is not needed for ActiveRecord < 7.1 (https://github.com/rails/rails/pull/47753).
+      def index_name(table_name, column_name)
+        max_index_name_size = 62
+        name = "index_#{table_name}_on_#{Array(column_name) * '_and_'}"
+        return name if name.bytesize <= max_index_name_size
+
+        # Fallback to short version, add hash to ensure uniqueness
+        hashed_identifier = "_#{OpenSSL::Digest::SHA256.hexdigest(name).first(10)}"
+        name = "idx_on_#{Array(column_name) * '_'}"
+
+        short_limit = max_index_name_size - hashed_identifier.bytesize
+        short_name = name[0, short_limit]
+
+        "#{short_name}#{hashed_identifier}"
+      end
+
       def ar_partial_writes?
         ActiveRecord::Base.public_send(ar_partial_writes_setting)
       end

test/schema_statements/changing_column_type_test.rb

@@ -261,6 +261,21 @@ def test_finalize_column_type_change_copies_indexes
       assert_equal(indexes_count, @connection.indexes(:projects).count { |index| index.columns.include?("name_for_type_change") })
     end
 
+    def test_finalize_column_type_change_copies_indexes_with_long_names
+      max_identifier_length = 63 # could use just `max_identifier_length` method for ActiveRecord >= 5.0.
+      long_column_name = "a" * (max_identifier_length - "index_projects_on_".length)
+
+      @connection.change_table(:projects) do |t|
+        t.text long_column_name
+        t.index long_column_name, name: "index_projects_on_#{long_column_name}"
+      end
+
+      @connection.initialize_column_type_change(:projects, long_column_name, :string)
+      @connection.finalize_column_type_change(:projects, long_column_name)
+
+      assert_equal(1, @connection.indexes(:projects).count { |index| index.columns.include?("#{long_column_name}_for_type_change") })
+    end
+
     def test_finalize_column_type_change_copies_foreign_key
       @connection.initialize_column_type_change(:projects, :user_id, :bigint)
       @connection.finalize_column_type_change(:projects, :user_id)