module ActiveRecord::ConnectionAdapters

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 65
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 < '5.0.0'
    raise "Your version of MySQL (#{full_version.match(/^\d+\.\d+\.\d+/)[0]}) is too old. Active Record supports MySQL >= 5.0."
  end
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 228
def begin_db_transaction
  execute "BEGIN"
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 232
def begin_isolated_db_transaction(isolation)
  execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
  begin_db_transaction
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 615
def case_sensitive_comparison(table, attribute, column, value)
  if !value.nil? && column.collation && !column.case_sensitive?
    table[attribute].eq(Arel::Nodes::Bin.new(Arel::Nodes::BindParam.new))
  else
    super
  end
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 300
def charset
  show_variable 'character_set_database'
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 198
def clear_cache!
  reload_type_map
  @statements.clear
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 305
def collation
  show_variable 'collation_database'
end

# File 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 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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 295
def current_database
  select_value 'SELECT DATABASE() as db'
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 347
def data_source_exists?(table_name)
  return false unless table_name.present?

  schema, name = extract_schema_qualified_name(table_name)

  sql = "SELECT table_name FROM information_schema.tables "
  sql << "WHERE table_schema = #{quote(schema)} AND table_name = #{quote(name)}"

  select_values(sql, 'SCHEMA').any?
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 325
def data_sources
  sql = "SELECT table_name FROM information_schema.tables "
  sql << "WHERE table_schema = #{quote(@config[:database])}"

  select_values(sql, 'SCHEMA')
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 465
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 257
def empty_insert_statement_value
  "VALUES ()"
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 217
def execute(sql, name = nil)
  log(sql, name) { @connection.query(sql) }
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 207
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 515
      def foreign_keys(table_name)
        raise ArgumentError unless table_name.present?

        schema, name = extract_schema_qualified_name(table_name)

        fk_info = select_all("          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 = #{quote(schema)}
            AND fk.table_name = #{quote(name)}
".strip_heredoc, 'SCHEMA')

        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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 160
def index_algorithms
  { default: 'ALGORITHM = DEFAULT', copy: 'ALGORITHM = COPY', inplace: 'ALGORITHM = INPLACE' }
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 156
def native_database_types
  NATIVE_DATABASE_TYPES
end

# File 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 lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 469
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 lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 445
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 594
def show_variable(name)
  select_value("SELECT @@#{name}", 'SCHEMA')
rescue ActiveRecord::StatementInvalid
  nil
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 643
def strict_mode?
  self.class.type_cast_config_to_boolean(@config.fetch(:strict, true))
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 144
def supports_advisory_locks?
  true
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 136
def supports_datetime_with_precision?
  if mariadb?
    version >= '5.3.0'
  else
    version >= '5.6.4'
  end
end

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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 128
def supports_foreign_keys?
  true
end

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

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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 92
def supports_migrations?
  true
end

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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 106
def supports_statement_cache?
  true
end

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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 132
def supports_views?
  true
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 336
      def table_exists?(table_name)
        # Update lib/active_record/internal_metadata.rb when this gets removed
        ActiveSupport::Deprecation.warn("          #table_exists? currently checks both tables and views.
          This behavior is deprecated and will be changed with Rails 5.1 to only check tables.
          Use #data_source_exists? instead.
".squish)

        data_source_exists?(table_name)
      end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 332
def truncate(table_name, name = nil)
  execute "TRUNCATE TABLE #{quote_table_name(table_name)}", name
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 571
def type_to_sql(type, limit = nil, precision = nil, scale = nil, unsigned = nil)
  sql = case type.to_s
  when 'integer'
    integer_to_sql(limit)
  when 'text'
    text_to_sql(limit)
  when 'blob'
    binary_to_sql(limit)
  when 'binary'
    if (0..0xfff) === limit
      "varbinary(#{limit})"
    else
      binary_to_sql(limit)
    end
  else
    super(type, limit, precision, scale)
  end

  sql << ' unsigned' if unsigned && type != :primary_key
  sql
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 647
def valid_type?(type)
  !native_database_types[type].nil?
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 747
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 715
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 791
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 729
def add_options_for_index_columns(quoted_columns, **options)
  quoted_columns = add_index_length(quoted_columns, options)
  super
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 802
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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 753
def change_column_sql(table_name, column_name, type, options = {})
  column = column_for(table_name, column_name)

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

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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 703
def extract_precision(sql_type)
  if /time/ === sql_type
    super || 0
  else
    super
  end
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 711
def fetch_type_metadata(sql_type, extra = "")
  MySQL::TypeMetadata.new(super(sql_type), extra: extra, strict: strict_mode?)
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 783
def remove_column_sql(table_name, column_name, type = nil, options = {})
  "DROP #{quote_column_name(column_name)}"
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 787
def remove_columns_sql(table_name, *column_names)
  column_names.map {|column_name| remove_column_sql(table_name, column_name) }
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 797
def remove_index_sql(table_name, options = {})
  index_name = index_name_for_remove(table_name, options)
  "DROP INDEX #{index_name}"
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 806
def remove_timestamps_sql(table_name, options = {})
  [remove_column_sql(table_name, :updated_at), remove_column_sql(table_name, :created_at)]
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 769
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 = select_one("SHOW COLUMNS FROM #{quote_table_name(table_name)} LIKE '#{column_name}'", 'SCHEMA')["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

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 734
def translate_exception(exception, message)
  case error_number(exception)
  when 1062
    RecordNotUnique.new(message)
  when 1452
    InvalidForeignKey.new(message)
  when 1406
    ValueTooLong.new(message)
  else
    super
  end
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 623
def can_perform_case_insensitive_comparison_for?(column)
  column.case_sensitive?
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 831
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 = @config[:wait_timeout]
  wait_timeout = 2147483 unless wait_timeout.is_a?(Integer)
  variables['wait_timeout'] = self.class.type_cast_config_to_integer(wait_timeout)

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

  # Make MySQL reject illegal values rather than truncating or blanking them, see
  # http://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
  # http://dev.mysql.com/doc/refman/5.7/en/set-statement.html#id944430
  # (trailing comma because variable_assignments will always have content)
  if @config[:encoding]
    encoding = "NAMES #{@config[:encoding]}"
    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
  @connection.query  "SET #{encoding} #{sql_mode_assignment} #{variable_assignments}"
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 814
def subquery_for(key, select)
  subsubselect = select.clone
  subsubselect.projections = [key]

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

  subselect = Arel::SelectManager.new(select.engine)
  subselect.project Arel.sql(key.name)
  subselect.from subsubselect.as('__active_record_temp')
end

# File lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 827
def supports_rename_index?
  mariadb? ? false : version >= '5.7.6'
end