class ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter

Constants

ER_CANNOT_ADD_FOREIGN
ER_CANNOT_CREATE_TABLE
ER_DATA_TOO_LONG
ER_DO_NOT_HAVE_DEFAULT
ER_DUP_ENTRY

See dev.mysql.com/doc/refman/5.7/en/error-messages-server.html

ER_LOCK_DEADLOCK
ER_LOCK_WAIT_TIMEOUT
ER_NOT_NULL_VIOLATION
ER_NO_REFERENCED_ROW_2
ER_OUT_OF_RANGE
NATIVE_DATABASE_TYPES

Public Class Methods

emulate_booleans() click to toggle source

By default, the Mysql2Adapter will consider all columns of type tinyint(1) as boolean. If you wish to disable this emulation you can add the following line to your application.rb file:

ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans = false
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 29
class_attribute :emulate_booleans, default: true
new(connection, logger, connection_options, config) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 53
def initialize(connection, logger, connection_options, config)
  super(connection, logger, config)

  @statements = StatementPool.new(self.class.type_cast_config_to_integer(config[:statement_limit]))

  if version < "5.1.10"
    raise "Your version of MySQL (#{version_string}) is too old. Active Record supports MySQL >= 5.1.10."
  end
end

Public Instance Methods

begin_db_transaction() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 199
def begin_db_transaction
  execute "BEGIN"
end
begin_isolated_db_transaction(isolation) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 203
def begin_isolated_db_transaction(isolation)
  execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
  begin_db_transaction
end
charset() click to toggle source

Returns the database character set.

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 271
def charset
  show_variable "character_set_database"
end
clear_cache!() click to toggle source

Clears the prepared statements cache.

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 165
def clear_cache!
  reload_type_map
  @statements.clear
end
collation() click to toggle source

Returns the database collation strategy.

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 276
def collation
  show_variable "collation_database"
end
create_database(name, options = {}) click to toggle source

Create a new MySQL database with optional :charset and :collation. Charset defaults to utf8.

Example:

create_database 'charset_test', charset: 'latin1', collation: 'latin1_bin'
create_database 'matt_development'
create_database 'matt_development', charset: :big5
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 250
def create_database(name, options = {})
  if options[:collation]
    execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT CHARACTER SET #{quote_table_name(options[:charset] || 'utf8')} COLLATE #{quote_table_name(options[:collation])}"
  else
    execute "CREATE DATABASE #{quote_table_name(name)} DEFAULT CHARACTER SET #{quote_table_name(options[:charset] || 'utf8')}"
  end
end
current_database() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 266
def current_database
  query_value("SELECT database()", "SCHEMA")
end
drop_table(table_name, options = {}) click to toggle source

Drops a table from the database.

:force

Set to :cascade to drop dependent objects as well. Defaults to false.

:if_exists

Set to true to only drop the table if it exists. Defaults to false.

:temporary

Set to true to drop temporary table. Defaults to false.

Although this command ignores most options and the block if one is given, it can be helpful to provide these in a migration's change method so it can be reverted. In that case, options and the block will be used by create_table.

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 338
def drop_table(table_name, options = {})
  execute "DROP#{' TEMPORARY' if options[:temporary]} TABLE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(table_name)}#{' CASCADE' if options[:force] == :cascade}"
end
empty_insert_statement_value() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 228
def empty_insert_statement_value
  "VALUES ()"
end
execute(sql, name = nil) click to toggle source

Executes the SQL statement in the context of this connection.

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 184
def execute(sql, name = nil)
  log(sql, name) do
    ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
      @connection.query(sql)
    end
  end
end
explain(arel, binds = []) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 174
def explain(arel, binds = [])
  sql     = "EXPLAIN #{to_sql(arel, binds)}"
  start   = Time.now
  result  = exec_query(sql, "EXPLAIN", binds)
  elapsed = Time.now - start

  MySQL::ExplainPrettyPrinter.new.pp(result, elapsed)
end
foreign_keys(table_name) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 388
      def foreign_keys(table_name)
        raise ArgumentError unless table_name.present?

        scope = quoted_scope(table_name)

        fk_info = exec_query(<<-SQL.strip_heredoc, "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',
                 rc.update_rule AS 'on_update',
                 rc.delete_rule AS 'on_delete'
          FROM information_schema.key_column_usage fk
          JOIN information_schema.referential_constraints rc
          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.table_name = #{scope[:name]}
        SQL

        fk_info.map do |row|
          options = {
            column: row["column"],
            name: row["name"],
            primary_key: row["primary_key"]
          }

          options[:on_update] = extract_foreign_key_action(row["on_update"])
          options[:on_delete] = extract_foreign_key_action(row["on_delete"])

          ForeignKeyDefinition.new(table_name, row["to_table"], options)
        end
      end
index_algorithms() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 131
def index_algorithms
  { default: "ALGORITHM = DEFAULT".dup, copy: "ALGORITHM = COPY".dup, inplace: "ALGORITHM = INPLACE".dup }
end
insert_fixtures(*) click to toggle source
Calls superclass method
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 526
def insert_fixtures(*)
  without_sql_mode("NO_AUTO_VALUE_ON_ZERO") { super }
end
native_database_types() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 127
def native_database_types
  NATIVE_DATABASE_TYPES
end
recreate_database(name, options = {}) click to toggle source

Drops the database specified on the name attribute and creates it again using the provided options.

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 236
def recreate_database(name, options = {})
  drop_database(name)
  sql = create_database(name, options)
  reconnect!
  sql
end
rename_index(table_name, old_name, new_name) click to toggle source
Calls superclass method
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 342
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
rename_table(table_name, new_name) click to toggle source

Renames a table.

Example:

rename_table('octopuses', 'octopi')
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 318
def rename_table(table_name, new_name)
  execute "RENAME TABLE #{quote_table_name(table_name)} TO #{quote_table_name(new_name)}"
  rename_table_indexes(table_name, new_name)
end
show_variable(name) click to toggle source

SHOW VARIABLES LIKE 'name'

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 469
def show_variable(name)
  query_value("SELECT @@#{name}", "SCHEMA")
rescue ActiveRecord::StatementInvalid
  nil
end
strict_mode?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 518
def strict_mode?
  self.class.type_cast_config_to_boolean(@config.fetch(:strict, true))
end
supports_advisory_locks?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 115
def supports_advisory_locks?
  true
end
supports_datetime_with_precision?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 99
def supports_datetime_with_precision?
  if mariadb?
    version >= "5.3.0"
  else
    version >= "5.6.4"
  end
end
supports_explain?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 83
def supports_explain?
  true
end
supports_foreign_keys?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 91
def supports_foreign_keys?
  true
end
supports_index_sort_order?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 75
def supports_index_sort_order?
  !mariadb? && version >= "8.0.1"
end
supports_indexes_in_create?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 87
def supports_indexes_in_create?
  true
end
supports_transaction_isolation?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 79
def supports_transaction_isolation?
  true
end
supports_views?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 95
def supports_views?
  true
end
supports_virtual_columns?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 107
def supports_virtual_columns?
  if mariadb?
    version >= "5.2.0"
  else
    version >= "5.7.5"
  end
end
truncate(table_name, name = nil) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 280
def truncate(table_name, name = nil)
  execute "TRUNCATE TABLE #{quote_table_name(table_name)}", name
end

Private Instance Methods

add_column_sql(table_name, column_name, type, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 663
def add_column_sql(table_name, column_name, type, options = {})
  td = create_table_definition(table_name)
  cd = td.new_column_definition(column_name, type, options)
  schema_creation.accept(AddColumnDefinition.new(cd))
end
add_index_length(quoted_columns, **options) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 603
def add_index_length(quoted_columns, **options)
  if length = options[:length]
    case length
    when Hash
      length = length.symbolize_keys
      quoted_columns.each { |name, column| column << "(#{length[name]})" if length[name].present? }
    when Integer
      quoted_columns.each { |name, column| column << "(#{length})" }
    end
  end

  quoted_columns
end
add_index_sql(table_name, column_name, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 711
def add_index_sql(table_name, column_name, options = {})
  index_name, index_type, index_columns, _, index_algorithm, index_using = add_index_options(table_name, column_name, options)
  index_algorithm[0, 0] = ", " if index_algorithm.present?
  "ADD #{index_type} INDEX #{quote_column_name(index_name)} #{index_using} (#{index_columns})#{index_algorithm}"
end
add_options_for_index_columns(quoted_columns, **options) click to toggle source
Calls superclass method
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 617
def add_options_for_index_columns(quoted_columns, **options)
  quoted_columns = add_index_length(quoted_columns, options)
  super
end
add_timestamps_sql(table_name, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 722
def add_timestamps_sql(table_name, options = {})
  [add_column_sql(table_name, :created_at, :datetime, options), add_column_sql(table_name, :updated_at, :datetime, options)]
end
arel_visitor() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 810
def arel_visitor
  Arel::Visitors::MySQL.new(self)
end
can_perform_case_insensitive_comparison_for?(column) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 498
def can_perform_case_insensitive_comparison_for?(column)
  column.case_sensitive?
end
change_column_sql(table_name, column_name, type, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 669
def change_column_sql(table_name, column_name, type, options = {})
  column = column_for(table_name, column_name)

  unless options.key?(:default)
    options[:default] = column.default
  end

  unless options.key?(:null)
    options[:null] = column.null
  end

  unless options.key?(:comment)
    options[:comment] = column.comment
  end

  td = create_table_definition(table_name)
  cd = td.new_column_definition(column.name, type, options)
  schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
end
configure_connection() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 747
def configure_connection
  variables = @config.fetch(:variables, {}).stringify_keys

  # By default, MySQL 'where id is null' selects the last inserted id; Turn this off.
  variables["sql_auto_is_null"] = 0

  # Increase timeout so the server doesn't disconnect us.
  wait_timeout = self.class.type_cast_config_to_integer(@config[:wait_timeout])
  wait_timeout = 2147483 unless wait_timeout.is_a?(Integer)
  variables["wait_timeout"] = wait_timeout

  defaults = [":default", :default].to_set

  # Make MySQL reject illegal values rather than truncating or blanking them, see
  # https://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_strict_all_tables
  # If the user has provided another value for sql_mode, don't replace it.
  if sql_mode = variables.delete("sql_mode")
    sql_mode = quote(sql_mode)
  elsif !defaults.include?(strict_mode?)
    if strict_mode?
      sql_mode = "CONCAT(@@sql_mode, ',STRICT_ALL_TABLES')"
    else
      sql_mode = "REPLACE(@@sql_mode, 'STRICT_TRANS_TABLES', '')"
      sql_mode = "REPLACE(#{sql_mode}, 'STRICT_ALL_TABLES', '')"
      sql_mode = "REPLACE(#{sql_mode}, 'TRADITIONAL', '')"
    end
    sql_mode = "CONCAT(#{sql_mode}, ',NO_AUTO_VALUE_ON_ZERO')"
  end
  sql_mode_assignment = "@@SESSION.sql_mode = #{sql_mode}, " if sql_mode

  # NAMES does not have an equals sign, see
  # https://dev.mysql.com/doc/refman/5.7/en/set-names.html
  # (trailing comma because variable_assignments will always have content)
  if @config[:encoding]
    encoding = "NAMES #{@config[:encoding]}".dup
    encoding << " COLLATE #{@config[:collation]}" if @config[:collation]
    encoding << ", "
  end

  # Gather up all of the SET variables...
  variable_assignments = variables.map do |k, v|
    if defaults.include?(v)
      "@@SESSION.#{k} = DEFAULT" # Sets the value to the global or compile default
    elsif !v.nil?
      "@@SESSION.#{k} = #{quote(v)}"
    end
    # or else nil; compact to clear nils out
  end.compact.join(", ")

  # ...and send them all in one query
  execute "SET #{encoding} #{sql_mode_assignment} #{variable_assignments}"
end
extract_precision(sql_type) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 595
def extract_precision(sql_type)
  if /\A(?:date)?time(?:stamp)?\b/.match?(sql_type)
    super || 0
  else
    super
  end
end
initialize_type_map(m = type_map) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 545
def initialize_type_map(m = type_map)
  super

  register_class_with_limit m, %r(char)i, MysqlString

  m.register_type %r(tinytext)i,   Type::Text.new(limit: 2**8 - 1)
  m.register_type %r(tinyblob)i,   Type::Binary.new(limit: 2**8 - 1)
  m.register_type %r(text)i,       Type::Text.new(limit: 2**16 - 1)
  m.register_type %r(blob)i,       Type::Binary.new(limit: 2**16 - 1)
  m.register_type %r(mediumtext)i, Type::Text.new(limit: 2**24 - 1)
  m.register_type %r(mediumblob)i, Type::Binary.new(limit: 2**24 - 1)
  m.register_type %r(longtext)i,   Type::Text.new(limit: 2**32 - 1)
  m.register_type %r(longblob)i,   Type::Binary.new(limit: 2**32 - 1)
  m.register_type %r(^float)i,     Type::Float.new(limit: 24)
  m.register_type %r(^double)i,    Type::Float.new(limit: 53)
  m.register_type %r(^json)i,      Type::Json.new

  register_integer_type m, %r(^bigint)i,    limit: 8
  register_integer_type m, %r(^int)i,       limit: 4
  register_integer_type m, %r(^mediumint)i, limit: 3
  register_integer_type m, %r(^smallint)i,  limit: 2
  register_integer_type m, %r(^tinyint)i,   limit: 1

  m.register_type %r(^tinyint\(1\))i, Type::Boolean.new if emulate_booleans
  m.alias_type %r(year)i,          "integer"
  m.alias_type %r(bit)i,           "binary"

  m.register_type(%r(enum)i) do |sql_type|
    limit = sql_type[/^enum\((.+)\)/i, 1]
      .split(",").map { |enum| enum.strip.length - 2 }.max
    MysqlString.new(limit: limit)
  end

  m.register_type(%r(^set)i) do |sql_type|
    limit = sql_type[/^set\((.+)\)/i, 1]
      .split(",").map { |set| set.strip.length - 1 }.sum - 1
    MysqlString.new(limit: limit)
  end
end
mismatched_foreign_key(message) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 814
def mismatched_foreign_key(message)
  parts = message.scan(/`(\w+)`[ $)]/).flatten
  MismatchedForeignKey.new(
    self,
    message: message,
    table: parts[0],
    foreign_key: parts[1],
    target_table: parts[2],
    primary_key: parts[3],
  )
end
register_integer_type(mapping, key, options) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 585
def register_integer_type(mapping, key, options)
  mapping.register_type(key) do |sql_type|
    if /\bunsigned\b/.match?(sql_type)
      Type::UnsignedInteger.new(options)
    else
      Type::Integer.new(options)
    end
  end
end
remove_column_sql(table_name, column_name, type = nil, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 703
def remove_column_sql(table_name, column_name, type = nil, options = {})
  "DROP #{quote_column_name(column_name)}"
end
remove_columns_sql(table_name, *column_names) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 707
def remove_columns_sql(table_name, *column_names)
  column_names.map { |column_name| remove_column_sql(table_name, column_name) }
end
remove_index_sql(table_name, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 717
def remove_index_sql(table_name, options = {})
  index_name = index_name_for_remove(table_name, options)
  "DROP INDEX #{index_name}"
end
remove_timestamps_sql(table_name, options = {}) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 726
def remove_timestamps_sql(table_name, options = {})
  [remove_column_sql(table_name, :updated_at), remove_column_sql(table_name, :created_at)]
end
rename_column_sql(table_name, column_name, new_column_name) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 689
def rename_column_sql(table_name, column_name, new_column_name)
  column  = column_for(table_name, column_name)
  options = {
    default: column.default,
    null: column.null,
    auto_increment: column.auto_increment?
  }

  current_type = exec_query("SHOW COLUMNS FROM #{quote_table_name(table_name)} LIKE #{quote(column_name)}", "SCHEMA").first["Type"]
  td = create_table_definition(table_name)
  cd = td.new_column_definition(new_column_name, current_type, options)
  schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
end
subquery_for(key, select) click to toggle source

MySQL is too stupid to create a temporary table for use subquery, so we have to give it some prompting in the form of a subsubquery. Ugh!

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 732
def subquery_for(key, select)
  subselect = select.clone
  subselect.projections = [key]

  # Materialize subquery by adding distinct
  # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
  subselect.distinct unless select.limit || select.offset || select.orders.any?

  Arel::SelectManager.new(subselect.as("__active_record_temp")).project(Arel.sql(key.name))
end
supports_rename_index?() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 743
def supports_rename_index?
  mariadb? ? false : version >= "5.7.6"
end
translate_exception(exception, message) click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 634
def translate_exception(exception, message)
  case error_number(exception)
  when ER_DUP_ENTRY
    RecordNotUnique.new(message)
  when ER_NO_REFERENCED_ROW_2
    InvalidForeignKey.new(message)
  when ER_CANNOT_ADD_FOREIGN
    mismatched_foreign_key(message)
  when ER_CANNOT_CREATE_TABLE
    if message.include?("errno: 150")
      mismatched_foreign_key(message)
    else
      super
    end
  when ER_DATA_TOO_LONG
    ValueTooLong.new(message)
  when ER_OUT_OF_RANGE
    RangeError.new(message)
  when ER_NOT_NULL_VIOLATION, ER_DO_NOT_HAVE_DEFAULT
    NotNullViolation.new(message)
  when ER_LOCK_DEADLOCK
    Deadlocked.new(message)
  when ER_LOCK_WAIT_TIMEOUT
    TransactionTimeout.new(message)
  else
    super
  end
end
version_string() click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 857
def version_string
  full_version.match(/^(?:5\.5\.5-)?(\d+\.\d+\.\d+)/)[1]
end
without_sql_mode(mode) { || ... } click to toggle source
# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 532
def without_sql_mode(mode)
  result = execute("SELECT @@SESSION.sql_mode")
  current_mode = result.first[0]
  return yield unless current_mode.include?(mode)

  sql_mode = "REPLACE(@@sql_mode, '#{mode}', '')"
  execute("SET @@SESSION.sql_mode = #{sql_mode}")
  yield
ensure
  sql_mode = "CONCAT(@@sql_mode, ',#{mode}')"
  execute("SET @@SESSION.sql_mode = #{sql_mode}")
end