# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 57
def dbconsole(config, options = {})
  mysql_config = config.configuration_hash

  args = {
    host: "--host",
    port: "--port",
    socket: "--socket",
    username: "--user",
    encoding: "--default-character-set",
    sslca: "--ssl-ca",
    sslcert: "--ssl-cert",
    sslcapath: "--ssl-capath",
    sslcipher: "--ssl-cipher",
    sslkey: "--ssl-key",
    ssl_mode: "--ssl-mode"
  }.filter_map { |opt, arg| "#{arg}=#{mysql_config[opt]}" if mysql_config[opt] }

  if mysql_config[:password] && options[:include_password]
    args << "--password=#{mysql_config[:password]}"
  elsif mysql_config[:password] && !mysql_config[:password].to_s.empty?
    args << "-p"
  end

  args << config.database

  find_cmd_and_exec(["mysql", "mysql5"], *args)
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 29
class_attribute :emulate_booleans, default: true

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 304
def charset
  show_variable "character_set_database"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 509
      def check_constraints(table_name)
        if supports_check_constraints?
          scope = quoted_scope(table_name)

          sql = <<~SQL
            SELECT cc.constraint_name AS 'name',
                  cc.check_clause AS 'expression'
            FROM information_schema.check_constraints cc
            JOIN information_schema.table_constraints tc
            USING (constraint_schema, constraint_name)
            WHERE tc.table_schema = #{scope[:schema]}
              AND tc.table_name = #{scope[:name]}
              AND cc.constraint_schema = #{scope[:schema]}
          SQL
          sql += " AND cc.table_name = #{scope[:name]}" if mariadb?

          chk_info = internal_exec_query(sql, "SCHEMA")

          chk_info.map do |row|
            options = {
              name: row["name"]
            }
            expression = row["expression"]
            expression = expression[1..-2] if expression.start_with?("(") && expression.end_with?(")")
            expression = strip_whitespace_characters(expression)

            unless mariadb?
              # MySQL returns check constraints expression in an already escaped form.
              # This leads to duplicate escaping later (e.g. when the expression is used in the SchemaDumper).
              expression = expression.gsub("\\'", "'")
            end

            CheckConstraintDefinition.new(table_name, expression, options)
          end
        else
          raise NotImplementedError
        end
      end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 309
def collation
  show_variable "collation_database"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 279
def create_database(name, options = {})
  if options[:collation]
    execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT COLLATE #{quote_table_name(options[:collation])}"
  elsif options[:charset]
    execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT CHARACTER SET #{quote_table_name(options[:charset])}"
  elsif row_format_dynamic_by_default?
    execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT CHARACTER SET `utf8mb4`"
  else
    raise "Configure a supported :charset and ensure innodb_large_prefix is enabled to support indexes on varchar(255) string columns."
  end
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 299
def current_database
  query_value("SELECT database()", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 357
def drop_table(table_name, **options)
  schema_cache.clear_data_source_cache!(table_name.to_s)
  execute "DROP#{' TEMPORARY' if options[:temporary]} TABLE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(table_name)}#{' CASCADE' if options[:force] == :cascade}"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 464
      def foreign_keys(table_name)
        raise ArgumentError unless table_name.present?

        scope = quoted_scope(table_name)

        # MySQL returns 1 row for each column of composite foreign keys.
        fk_info = internal_exec_query(<<~SQL, "SCHEMA")
          SELECT fk.referenced_table_name AS 'to_table',
                 fk.referenced_column_name AS 'primary_key',
                 fk.column_name AS 'column',
                 fk.constraint_name AS 'name',
                 fk.ordinal_position AS 'position',
                 rc.update_rule AS 'on_update',
                 rc.delete_rule AS 'on_delete'
          FROM information_schema.referential_constraints rc
          JOIN information_schema.key_column_usage fk
          USING (constraint_schema, constraint_name)
          WHERE fk.referenced_column_name IS NOT NULL
            AND fk.table_schema = #{scope[:schema]}
            AND fk.table_name = #{scope[:name]}
            AND rc.constraint_schema = #{scope[:schema]}
            AND rc.table_name = #{scope[:name]}
        SQL

        grouped_fk = fk_info.group_by { |row| row["name"] }.values.each { |group| group.sort_by! { |row| row["position"] } }
        grouped_fk.map do |group|
          row = group.first
          options = {
            name: row["name"],
            on_update: extract_foreign_key_action(row["on_update"]),
            on_delete: extract_foreign_key_action(row["on_delete"])
          }

          if group.one?
            options[:column] = unquote_identifier(row["column"])
            options[:primary_key] = row["primary_key"]
          else
            options[:column] = group.map { |row| unquote_identifier(row["column"]) }
            options[:primary_key] = group.map { |row| row["primary_key"] }
          end

          ForeignKeyDefinition.new(table_name, unquote_identifier(row["to_table"]), options)
        end
      end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 185
def index_algorithms
  {
    default: "ALGORITHM = DEFAULT",
    copy:    "ALGORITHM = COPY",
    inplace: "ALGORITHM = INPLACE",
    instant: "ALGORITHM = INSTANT",
  }
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 181
def native_database_types
  NATIVE_DATABASE_TYPES
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 265
def recreate_database(name, options = {})
  drop_database(name)
  sql = create_database(name, options)
  reconnect!
  sql
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 362
def rename_index(table_name, old_name, new_name)
  if supports_rename_index?
    validate_index_length!(table_name, new_name)

    execute "ALTER TABLE #{quote_table_name(table_name)} RENAME INDEX #{quote_table_name(old_name)} TO #{quote_table_name(new_name)}"
  else
    super
  end
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 334
def rename_table(table_name, new_name, **options)
  validate_table_length!(new_name) unless options[:_uses_legacy_table_name]
  schema_cache.clear_data_source_cache!(table_name.to_s)
  schema_cache.clear_data_source_cache!(new_name.to_s)
  execute "RENAME TABLE #{quote_table_name(table_name)} TO #{quote_table_name(new_name)}"
  rename_table_indexes(table_name, new_name)
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 578
def show_variable(name)
  query_value("SELECT @@#{name}", "SCHEMA")
rescue ActiveRecord::StatementInvalid
  nil
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 629
def strict_mode?
  self.class.type_cast_config_to_boolean(@config.fetch(:strict, true))
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 161
def supports_advisory_locks?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 96
def supports_bulk_alter?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 128
def supports_check_constraints?
  if mariadb?
    database_version >= "10.3.10" || (database_version < "10.3" && database_version >= "10.2.22")
  else
    database_version >= "8.0.16"
  end
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 153
def supports_common_table_expressions?
  if mariadb?
    database_version >= "10.2.1"
  else
    database_version >= "8.0.1"
  end
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 140
def supports_datetime_with_precision?
  mariadb? || database_version >= "5.6.4"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 116
def supports_explain?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 104
def supports_expression_index?
  !mariadb? && database_version >= "8.0.13"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 124
def supports_foreign_keys?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 100
def supports_index_sort_order?
  !mariadb? && database_version >= "8.0.1"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 120
def supports_indexes_in_create?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 165
def supports_insert_on_duplicate_skip?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 169
def supports_insert_on_duplicate_update?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 149
def supports_optimizer_hints?
  !mariadb? && database_version >= "5.7.7"
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 112
def supports_restart_db_transaction?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 108
def supports_transaction_isolation?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 136
def supports_views?
  true
end

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 144
def supports_virtual_columns?
  mariadb? || database_version >= "5.7.5"
end