text: import datetime
  import decimal
  import hashlib
  import logging
  from time import time
  
  from django.conf import settings
  from django.utils.encoding import force_bytes
  from django.utils.timezone import utc
  
  logger = logging.getLogger('django.db.backends')
  
  
  class CursorWrapper:
      def __init__(self, cursor, db):
          self.cursor = cursor
          self.db = db
  
      WRAP_ERROR_ATTRS = frozenset(['fetchone', 'fetchmany', 'fetchall', 'nextset'])
  
      def __getattr__(self, attr):
          cursor_attr = getattr(self.cursor, attr)
          if attr in CursorWrapper.WRAP_ERROR_ATTRS:
              return self.db.wrap_database_errors(cursor_attr)
          else:
              return cursor_attr
  
      def __iter__(self):
          with self.db.wrap_database_errors:
              for item in self.cursor:
                  yield item
  
      def __enter__(self):
          return self
  
      def __exit__(self, type, value, traceback):
          # Close instead of passing through to avoid backend-specific behavior
          # (#17671). Catch errors liberally because errors in cleanup code
          # aren't useful.
          try:
              self.close()
          except self.db.Database.Error:
              pass
  
      # The following methods cannot be implemented in __getattr__, because the
      # code must run when the method is invoked, not just when it is accessed.
  
      def callproc(self, procname, params=None):
          self.db.validate_no_broken_transaction()
          with self.db.wrap_database_errors:
              if params is None:
                  return self.cursor.callproc(procname)
              else:
                  return self.cursor.callproc(procname, params)
  
      def execute(self, sql, params=None):
          self.db.validate_no_broken_transaction()
          with self.db.wrap_database_errors:
              if params is None:
                  return self.cursor.execute(sql)
              else:
                  return self.cursor.execute(sql, params)
  
      def executemany(self, sql, param_list):
          self.db.validate_no_broken_transaction()
          with self.db.wrap_database_errors:
              return self.cursor.executemany(sql, param_list)
  
  
  class CursorDebugWrapper(CursorWrapper):
  
      # XXX callproc isn't instrumented at this time.
  
      def execute(self, sql, params=None):
          start = time()
          try:
              return super(CursorDebugWrapper, self).execute(sql, params)
          finally:
              stop = time()
              duration = stop - start
              sql = self.db.ops.last_executed_query(self.cursor, sql, params)
              self.db.queries_log.append({
                  'sql': sql,
                  'time': "%.3f" % duration,
              })
              logger.debug(
                  '(%.3f) %s; args=%s', duration, sql, params,
                  extra={'duration': duration, 'sql': sql, 'params': params}
              )
  
      def executemany(self, sql, param_list):
          start = time()
          try:
              return super(CursorDebugWrapper, self).executemany(sql, param_list)
          finally:
              stop = time()
              duration = stop - start
              try:
                  times = len(param_list)
              except TypeError:           # param_list could be an iterator
                  times = '?'
              self.db.queries_log.append({
                  'sql': '%s times: %s' % (times, sql),
                  'time': "%.3f" % duration,
              })
              logger.debug(
                  '(%.3f) %s; args=%s', duration, sql, param_list,
                  extra={'duration': duration, 'sql': sql, 'params': param_list}
              )
  
  
  ###############################################
  # Converters from database (string) to Python #
  ###############################################
  
  def typecast_date(s):
      return datetime.date(*map(int, s.split('-'))) if s else None  # returns None if s is null
  
  
  def typecast_time(s):  # does NOT store time zone information
      if not s:
          return None
      hour, minutes, seconds = s.split(':')
      if '.' in seconds:  # check whether seconds have a fractional part
          seconds, microseconds = seconds.split('.')
      else:
          microseconds = '0'
      return datetime.time(int(hour), int(minutes), int(seconds), int((microseconds + '000000')[:6]))
  
  
  def typecast_timestamp(s):  # does NOT store time zone information
      # "2005-07-29 15:48:00.590358-05"
      # "2005-07-29 09:56:00-05"
      if not s:
          return None
      if ' ' not in s:
          return typecast_date(s)
      d, t = s.split()
      # Extract timezone information, if it exists. Currently we just throw
      # it away, but in the future we may make use of it.
      if '-' in t:
          t, tz = t.split('-', 1)
          tz = '-' + tz
      elif '+' in t:
          t, tz = t.split('+', 1)
          tz = '+' + tz
      else:
          tz = ''
      dates = d.split('-')
      times = t.split(':')
      seconds = times[2]
      if '.' in seconds:  # check whether seconds have a fractional part
          seconds, microseconds = seconds.split('.')
      else:
          microseconds = '0'
      tzinfo = utc if settings.USE_TZ else None
      return datetime.datetime(
          int(dates[0]), int(dates[1]), int(dates[2]),
          int(times[0]), int(times[1]), int(seconds),
          int((microseconds + '000000')[:6]), tzinfo
      )
  
  
  def typecast_decimal(s):
      if s is None or s == '':
          return None
      return decimal.Decimal(s)
  
  
  ###############################################
  # Converters from Python to database (string) #
  ###############################################
  
  def rev_typecast_decimal(d):
      if d is None:
          return None
      return str(d)
  
  
  def truncate_name(name, length=None, hash_len=4):
      """Shortens a string to a repeatable mangled version with the given length.
      """
      if length is None or len(name) <= length:
          return name
  
      hsh = hashlib.md5(force_bytes(name)).hexdigest()[:hash_len]
      return '%s%s' % (name[:length - hash_len], hsh)
  
  
  def format_number(value, max_digits, decimal_places):
      """
      Formats a number into a string with the requisite number of digits and
      decimal places.
      """
      if value is None:
          return None
      if isinstance(value, decimal.Decimal):
          context = decimal.getcontext().copy()
          if max_digits is not None:
              context.prec = max_digits
          if decimal_places is not None:
              value = value.quantize(decimal.Decimal(".1") ** decimal_places, context=context)
          else:
              context.traps[decimal.Rounded] = 1
              value = context.create_decimal(value)
          return "{:f}".format(value)
      if decimal_places is not None:
          return "%.*f" % (decimal_places, value)
      return "{:f}".format(value)
  
  
  def strip_quotes(table_name):
      """
      Strip quotes off of quoted table names to make them safe for use in index
      names, sequence names, etc. For example '"USER"."TABLE"' (an Oracle naming
      scheme) becomes 'USER"."TABLE'.
      """
      has_quotes = table_name.startswith('"') and table_name.endswith('"')
      return table_name[1:-1] if has_quotes else table_name
  