text: """
  Oracle database backend for Django.
  
  Requires cx_Oracle: https://oracle.github.io/python-cx_Oracle/
  """
  import datetime
  import decimal
  import os
  import platform
  
  from django.conf import settings
  from django.core.exceptions import ImproperlyConfigured
  from django.db import utils
  from django.db.backends.base.base import BaseDatabaseWrapper
  from django.utils.encoding import force_bytes, force_text
  from django.utils.functional import cached_property
  
  
  def _setup_environment(environ):
      # Cygwin requires some special voodoo to set the environment variables
      # properly so that Oracle will see them.
      if platform.system().upper().startswith('CYGWIN'):
          try:
              import ctypes
          except ImportError as e:
              raise ImproperlyConfigured("Error loading ctypes: %s; "
                                         "the Oracle backend requires ctypes to "
                                         "operate correctly under Cygwin." % e)
          kernel32 = ctypes.CDLL('kernel32')
          for name, value in environ:
              kernel32.SetEnvironmentVariableA(name, value)
      else:
          os.environ.update(environ)
  
  
  _setup_environment([
      # Oracle takes client-side character set encoding from the environment.
      ('NLS_LANG', '.AL32UTF8'),
      # This prevents unicode from getting mangled by getting encoded into the
      # potentially non-unicode database character set.
      ('ORA_NCHAR_LITERAL_REPLACE', 'TRUE'),
  ])
  
  
  try:
      import cx_Oracle as Database
  except ImportError as e:
      raise ImproperlyConfigured("Error loading cx_Oracle module: %s" % e)
  
  # Some of these import cx_Oracle, so import them after checking if it's installed.
  from .client import DatabaseClient                          # NOQA isort:skip
  from .creation import DatabaseCreation                      # NOQA isort:skip
  from .features import DatabaseFeatures                      # NOQA isort:skip
  from .introspection import DatabaseIntrospection            # NOQA isort:skip
  from .operations import DatabaseOperations                  # NOQA isort:skip
  from .schema import DatabaseSchemaEditor                    # NOQA isort:skip
  from .utils import Oracle_datetime                          # NOQA isort:skip
  from .validation import DatabaseValidation                  # NOQA isort:skip
  
  
  class _UninitializedOperatorsDescriptor:
  
      def __get__(self, instance, cls=None):
          # If connection.operators is looked up before a connection has been
          # created, transparently initialize connection.operators to avert an
          # AttributeError.
          if instance is None:
              raise AttributeError("operators not available as class attribute")
          # Creating a cursor will initialize the operators.
          instance.cursor().close()
          return instance.__dict__['operators']
  
  
  class DatabaseWrapper(BaseDatabaseWrapper):
      vendor = 'oracle'
      display_name = 'Oracle'
      # This dictionary maps Field objects to their associated Oracle column
      # types, as strings. Column-type strings can contain format strings; they'll
      # be interpolated against the values of Field.__dict__ before being output.
      # If a column type is set to None, it won't be included in the output.
      #
      # Any format strings starting with "qn_" are quoted before being used in the
      # output (the "qn_" prefix is stripped before the lookup is performed.
      data_types = {
          'AutoField': 'NUMBER(11) GENERATED BY DEFAULT ON NULL AS IDENTITY',
          'BigAutoField': 'NUMBER(19) GENERATED BY DEFAULT ON NULL AS IDENTITY',
          'BinaryField': 'BLOB',
          'BooleanField': 'NUMBER(1)',
          'CharField': 'NVARCHAR2(%(max_length)s)',
          'DateField': 'DATE',
          'DateTimeField': 'TIMESTAMP',
          'DecimalField': 'NUMBER(%(max_digits)s, %(decimal_places)s)',
          'DurationField': 'INTERVAL DAY(9) TO SECOND(6)',
          'FileField': 'NVARCHAR2(%(max_length)s)',
          'FilePathField': 'NVARCHAR2(%(max_length)s)',
          'FloatField': 'DOUBLE PRECISION',
          'IntegerField': 'NUMBER(11)',
          'BigIntegerField': 'NUMBER(19)',
          'IPAddressField': 'VARCHAR2(15)',
          'GenericIPAddressField': 'VARCHAR2(39)',
          'NullBooleanField': 'NUMBER(1)',
          'OneToOneField': 'NUMBER(11)',
          'PositiveIntegerField': 'NUMBER(11)',
          'PositiveSmallIntegerField': 'NUMBER(11)',
          'SlugField': 'NVARCHAR2(%(max_length)s)',
          'SmallIntegerField': 'NUMBER(11)',
          'TextField': 'NCLOB',
          'TimeField': 'TIMESTAMP',
          'URLField': 'VARCHAR2(%(max_length)s)',
          'UUIDField': 'VARCHAR2(32)',
      }
      data_type_check_constraints = {
          'BooleanField': '%(qn_column)s IN (0,1)',
          'NullBooleanField': '%(qn_column)s IN (0,1)',
          'PositiveIntegerField': '%(qn_column)s >= 0',
          'PositiveSmallIntegerField': '%(qn_column)s >= 0',
      }
  
      # Oracle doesn't support a database index on these columns.
      _limited_data_types = ('clob', 'nclob', 'blob')
  
      operators = _UninitializedOperatorsDescriptor()
  
      _standard_operators = {
          'exact': '= %s',
          'iexact': '= UPPER(%s)',
          'contains': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
          'icontains': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
          'gt': '> %s',
          'gte': '>= %s',
          'lt': '< %s',
          'lte': '<= %s',
          'startswith': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
          'endswith': "LIKE TRANSLATE(%s USING NCHAR_CS) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
          'istartswith': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
          'iendswith': "LIKE UPPER(TRANSLATE(%s USING NCHAR_CS)) ESCAPE TRANSLATE('\\' USING NCHAR_CS)",
      }
  
      _likec_operators = {
          **_standard_operators,
          'contains': "LIKEC %s ESCAPE '\\'",
          'icontains': "LIKEC UPPER(%s) ESCAPE '\\'",
          'startswith': "LIKEC %s ESCAPE '\\'",
          'endswith': "LIKEC %s ESCAPE '\\'",
          'istartswith': "LIKEC UPPER(%s) ESCAPE '\\'",
          'iendswith': "LIKEC UPPER(%s) ESCAPE '\\'",
      }
  
      # The patterns below are used to generate SQL pattern lookup clauses when
      # the right-hand side of the lookup isn't a raw string (it might be an expression
      # or the result of a bilateral transformation).
      # In those cases, special characters for LIKE operators (e.g. \, %, _)
      # should be escaped on the database side.
      #
      # Note: we use str.format() here for readability as '%' is used as a wildcard for
      # the LIKE operator.
      pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\', '\\'), '%%', '\%%'), '_', '\_')"
      _pattern_ops = {
          'contains': "'%%' || {} || '%%'",
          'icontains': "'%%' || UPPER({}) || '%%'",
          'startswith': "{} || '%%'",
          'istartswith': "UPPER({}) || '%%'",
          'endswith': "'%%' || {}",
          'iendswith': "'%%' || UPPER({})",
      }
  
      _standard_pattern_ops = {k: "LIKE TRANSLATE( " + v + " USING NCHAR_CS)"
                                  " ESCAPE TRANSLATE('\\' USING NCHAR_CS)"
                               for k, v in _pattern_ops.items()}
      _likec_pattern_ops = {k: "LIKEC " + v + " ESCAPE '\\'"
                            for k, v in _pattern_ops.items()}
  
      Database = Database
      SchemaEditorClass = DatabaseSchemaEditor
      # Classes instantiated in __init__().
      client_class = DatabaseClient
      creation_class = DatabaseCreation
      features_class = DatabaseFeatures
      introspection_class = DatabaseIntrospection
      ops_class = DatabaseOperations
      validation_class = DatabaseValidation
  
      def __init__(self, *args, **kwargs):
          super().__init__(*args, **kwargs)
          use_returning_into = self.settings_dict["OPTIONS"].get('use_returning_into', True)
          self.features.can_return_id_from_insert = use_returning_into
  
      def _dsn(self):
          settings_dict = self.settings_dict
          if not settings_dict['HOST'].strip():
              settings_dict['HOST'] = 'localhost'
          if settings_dict['PORT']:
              return Database.makedsn(settings_dict['HOST'], int(settings_dict['PORT']), settings_dict['NAME'])
          return settings_dict['NAME']
  
      def _connect_string(self):
          return '%s/\\"%s\\"@%s' % (self.settings_dict['USER'], self.settings_dict['PASSWORD'], self._dsn())
  
      def get_connection_params(self):
          conn_params = self.settings_dict['OPTIONS'].copy()
          if 'use_returning_into' in conn_params:
              del conn_params['use_returning_into']
          return conn_params
  
      def get_new_connection(self, conn_params):
          return Database.connect(
              user=self.settings_dict['USER'],
              password=self.settings_dict['PASSWORD'],
              dsn=self._dsn(),
              **conn_params,
          )
  
      def init_connection_state(self):
          cursor = self.create_cursor()
          # Set the territory first. The territory overrides NLS_DATE_FORMAT
          # and NLS_TIMESTAMP_FORMAT to the territory default. When all of
          # these are set in single statement it isn't clear what is supposed
          # to happen.
          cursor.execute("ALTER SESSION SET NLS_TERRITORY = 'AMERICA'")
          # Set Oracle date to ANSI date format.  This only needs to execute
          # once when we create a new connection. We also set the Territory
          # to 'AMERICA' which forces Sunday to evaluate to a '1' in
          # TO_CHAR().
          cursor.execute(
              "ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'"
              " NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'" +
              (" TIME_ZONE = 'UTC'" if settings.USE_TZ else '')
          )
          cursor.close()
          if 'operators' not in self.__dict__:
              # Ticket #14149: Check whether our LIKE implementation will
              # work for this connection or we need to fall back on LIKEC.
              # This check is performed only once per DatabaseWrapper
              # instance per thread, since subsequent connections will use
              # the same settings.
              cursor = self.create_cursor()
              try:
                  cursor.execute("SELECT 1 FROM DUAL WHERE DUMMY %s"
                                 % self._standard_operators['contains'],
                                 ['X'])
              except Database.DatabaseError:
                  self.operators = self._likec_operators
                  self.pattern_ops = self._likec_pattern_ops
              else:
                  self.operators = self._standard_operators
                  self.pattern_ops = self._standard_pattern_ops
              cursor.close()
          self.connection.stmtcachesize = 20
          # Ensure all changes are preserved even when AUTOCOMMIT is False.
          if not self.get_autocommit():
              self.commit()
  
      def create_cursor(self, name=None):
          return FormatStylePlaceholderCursor(self.connection)
  
      def _commit(self):
          if self.connection is not None:
              try:
                  return self.connection.commit()
              except Database.DatabaseError as e:
                  # cx_Oracle raises a cx_Oracle.DatabaseError exception
                  # with the following attributes and values:
                  #  code = 2091
                  #  message = 'ORA-02091: transaction rolled back
                  #            'ORA-02291: integrity constraint (TEST_DJANGOTEST.SYS
                  #               _C00102056) violated - parent key not found'
                  # We convert that particular case to our IntegrityError exception
                  x = e.args[0]
                  if hasattr(x, 'code') and hasattr(x, 'message') \
                     and x.code == 2091 and 'ORA-02291' in x.message:
                      raise utils.IntegrityError(*tuple(e.args))
                  raise
  
      # Oracle doesn't support releasing savepoints. But we fake them when query
      # logging is enabled to keep query counts consistent with other backends.
      def _savepoint_commit(self, sid):
          if self.queries_logged:
              self.queries_log.append({
                  'sql': '-- RELEASE SAVEPOINT %s (faked)' % self.ops.quote_name(sid),
                  'time': '0.000',
              })
  
      def _set_autocommit(self, autocommit):
          with self.wrap_database_errors:
              self.connection.autocommit = autocommit
  
      def check_constraints(self, table_names=None):
          """
          Check constraints by setting them to immediate. Return them to deferred
          afterward.
          """
          self.cursor().execute('SET CONSTRAINTS ALL IMMEDIATE')
          self.cursor().execute('SET CONSTRAINTS ALL DEFERRED')
  
      def is_usable(self):
          try:
              self.connection.ping()
          except Database.Error:
              return False
          else:
              return True
  
      @cached_property
      def oracle_version(self):
          with self.temporary_connection():
              return tuple(int(x) for x in self.connection.version.split('.'))
  
  
  class OracleParam:
      """
      Wrapper object for formatting parameters for Oracle. If the string
      representation of the value is large enough (greater than 4000 characters)
      the input size needs to be set as CLOB. Alternatively, if the parameter
      has an `input_size` attribute, then the value of the `input_size` attribute
      will be used instead. Otherwise, no input size will be set for the
      parameter when executing the query.
      """
  
      def __init__(self, param, cursor, strings_only=False):
          # With raw SQL queries, datetimes can reach this function
          # without being converted by DateTimeField.get_db_prep_value.
          if settings.USE_TZ and (isinstance(param, datetime.datetime) and
                                  not isinstance(param, Oracle_datetime)):
              param = Oracle_datetime.from_datetime(param)
  
          string_size = 0
          # Oracle doesn't recognize True and False correctly.
          if param is True:
              param = 1
          elif param is False:
              param = 0
          if hasattr(param, 'bind_parameter'):
              self.force_bytes = param.bind_parameter(cursor)
          elif isinstance(param, (Database.Binary, datetime.timedelta)):
              self.force_bytes = param
          else:
              # To transmit to the database, we need Unicode if supported
              # To get size right, we must consider bytes.
              self.force_bytes = force_text(param, cursor.charset, strings_only)
              if isinstance(self.force_bytes, str):
                  # We could optimize by only converting up to 4000 bytes here
                  string_size = len(force_bytes(param, cursor.charset, strings_only))
          if hasattr(param, 'input_size'):
              # If parameter has `input_size` attribute, use that.
              self.input_size = param.input_size
          elif string_size > 4000:
              # Mark any string param greater than 4000 characters as a CLOB.
              self.input_size = Database.CLOB
          elif isinstance(param, datetime.datetime):
              self.input_size = Database.TIMESTAMP
          else:
              self.input_size = None
  
  
  class VariableWrapper:
      """
      An adapter class for cursor variables that prevents the wrapped object
      from being converted into a string when used to instantiate an OracleParam.
      This can be used generally for any other object that should be passed into
      Cursor.execute as-is.
      """
  
      def __init__(self, var):
          self.var = var
  
      def bind_parameter(self, cursor):
          return self.var
  
      def __getattr__(self, key):
          return getattr(self.var, key)
  
      def __setattr__(self, key, value):
          if key == 'var':
              self.__dict__[key] = value
          else:
              setattr(self.var, key, value)
  
  
  class FormatStylePlaceholderCursor:
      """
      Django uses "format" (e.g. '%s') style placeholders, but Oracle uses ":var"
      style. This fixes it -- but note that if you want to use a literal "%s" in
      a query, you'll need to use "%%s".
      """
      charset = 'utf-8'
  
      def __init__(self, connection):
          self.cursor = connection.cursor()
          self.cursor.outputtypehandler = self._output_type_handler
  
      @staticmethod
      def _output_number_converter(value):
          return decimal.Decimal(value) if '.' in value else int(value)
  
      @staticmethod
      def _get_decimal_converter(precision, scale):
          if scale == 0:
              return int
          context = decimal.Context(prec=precision)
          quantize_value = decimal.Decimal(1).scaleb(-scale)
          return lambda v: decimal.Decimal(v).quantize(quantize_value, context=context)
  
      @staticmethod
      def _output_type_handler(cursor, name, defaultType, length, precision, scale):
          """
          Called for each db column fetched from cursors. Return numbers as the
          appropriate Python type.
          """
          if defaultType == Database.NUMBER:
              if scale == -127:
                  if precision == 0:
                      # NUMBER column: decimal-precision floating point.
                      # This will normally be an integer from a sequence,
                      # but it could be a decimal value.
                      outconverter = FormatStylePlaceholderCursor._output_number_converter
                  else:
                      # FLOAT column: binary-precision floating point.
                      # This comes from FloatField columns.
                      outconverter = float
              elif precision > 0:
                  # NUMBER(p,s) column: decimal-precision fixed point.
                  # This comes from IntegerField and DecimalField columns.
                  outconverter = FormatStylePlaceholderCursor._get_decimal_converter(precision, scale)
              else:
                  # No type information. This normally comes from a
                  # mathematical expression in the SELECT list. Guess int
                  # or Decimal based on whether it has a decimal point.
                  outconverter = FormatStylePlaceholderCursor._output_number_converter
              return cursor.var(
                  Database.STRING,
                  size=255,
                  arraysize=cursor.arraysize,
                  outconverter=outconverter,
              )
  
      def _format_params(self, params):
          try:
              return {k: OracleParam(v, self, True) for k, v in params.items()}
          except AttributeError:
              return tuple(OracleParam(p, self, True) for p in params)
  
      def _guess_input_sizes(self, params_list):
          # Try dict handling; if that fails, treat as sequence
          if hasattr(params_list[0], 'keys'):
              sizes = {}
              for params in params_list:
                  for k, value in params.items():
                      if value.input_size:
                          sizes[k] = value.input_size
              if sizes:
                  self.setinputsizes(**sizes)
          else:
              # It's not a list of dicts; it's a list of sequences
              sizes = [None] * len(params_list[0])
              for params in params_list:
                  for i, value in enumerate(params):
                      if value.input_size:
                          sizes[i] = value.input_size
              if sizes:
                  self.setinputsizes(*sizes)
  
      def _param_generator(self, params):
          # Try dict handling; if that fails, treat as sequence
          if hasattr(params, 'items'):
              return {k: v.force_bytes for k, v in params.items()}
          else:
              return [p.force_bytes for p in params]
  
      def _fix_for_params(self, query, params, unify_by_values=False):
          # cx_Oracle wants no trailing ';' for SQL statements.  For PL/SQL, it
          # it does want a trailing ';' but not a trailing '/'.  However, these
          # characters must be included in the original query in case the query
          # is being passed to SQL*Plus.
          if query.endswith(';') or query.endswith('/'):
              query = query[:-1]
          if params is None:
              params = []
          elif hasattr(params, 'keys'):
              # Handle params as dict
              args = {k: ":%s" % k for k in params}
              query = query % args
          elif unify_by_values and params:
              # Handle params as a dict with unified query parameters by their
              # values. It can be used only in single query execute() because
              # executemany() shares the formatted query with each of the params
              # list. e.g. for input params = [0.75, 2, 0.75, 'sth', 0.75]
              # params_dict = {0.75: ':arg0', 2: ':arg1', 'sth': ':arg2'}
              # args = [':arg0', ':arg1', ':arg0', ':arg2', ':arg0']
              # params = {':arg0': 0.75, ':arg1': 2, ':arg2': 'sth'}
              params_dict = {param: ':arg%d' % i for i, param in enumerate(set(params))}
              args = [params_dict[param] for param in params]
              params = {value: key for key, value in params_dict.items()}
              query = query % tuple(args)
          else:
              # Handle params as sequence
              args = [(':arg%d' % i) for i in range(len(params))]
              query = query % tuple(args)
          return query, self._format_params(params)
  
      def execute(self, query, params=None):
          query, params = self._fix_for_params(query, params, unify_by_values=True)
          self._guess_input_sizes([params])
          return self.cursor.execute(query, self._param_generator(params))
  
      def executemany(self, query, params=None):
          if not params:
              # No params given, nothing to do
              return None
          # uniform treatment for sequences and iterables
          params_iter = iter(params)
          query, firstparams = self._fix_for_params(query, next(params_iter))
          # we build a list of formatted params; as we're going to traverse it
          # more than once, we can't make it lazy by using a generator
          formatted = [firstparams] + [self._format_params(p) for p in params_iter]
          self._guess_input_sizes(formatted)
          return self.cursor.executemany(query, [self._param_generator(p) for p in formatted])
  
      def close(self):
          try:
              self.cursor.close()
          except Database.InterfaceError:
              # already closed
              pass
  
      def var(self, *args):
          return VariableWrapper(self.cursor.var(*args))
  
      def arrayvar(self, *args):
          return VariableWrapper(self.cursor.arrayvar(*args))
  
      def __getattr__(self, attr):
          return getattr(self.cursor, attr)
  
      def __iter__(self):
          return iter(self.cursor)
  