1394 lines
48 KiB
Python
1394 lines
48 KiB
Python
import datetime
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import time
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from django.db.utils import DatabaseError
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try:
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from django.utils.six.moves import _thread as thread
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except ImportError:
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from django.utils.six.moves import _dummy_thread as thread
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from collections import namedtuple
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from contextlib import contextmanager
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from importlib import import_module
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from django.conf import settings
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from django.db import DEFAULT_DB_ALIAS
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from django.db.backends.signals import connection_created
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from django.db.backends import util
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from django.db.transaction import TransactionManagementError
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from django.db.utils import DatabaseErrorWrapper
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from django.utils.functional import cached_property
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from django.utils import six
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from django.utils import timezone
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class BaseDatabaseWrapper(object):
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"""
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Represents a database connection.
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"""
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ops = None
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vendor = 'unknown'
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def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS,
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allow_thread_sharing=False):
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# `settings_dict` should be a dictionary containing keys such as
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# NAME, USER, etc. It's called `settings_dict` instead of `settings`
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# to disambiguate it from Django settings modules.
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self.connection = None
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self.queries = []
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self.settings_dict = settings_dict
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self.alias = alias
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self.use_debug_cursor = None
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# Savepoint management related attributes
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self.savepoint_state = 0
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# Transaction management related attributes
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self.autocommit = False
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self.transaction_state = []
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# Tracks if the connection is believed to be in transaction. This is
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# set somewhat aggressively, as the DBAPI doesn't make it easy to
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# deduce if the connection is in transaction or not.
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self._dirty = False
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# Tracks if the connection is in a transaction managed by 'atomic'.
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self.in_atomic_block = False
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# List of savepoints created by 'atomic'
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self.savepoint_ids = []
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# Tracks if the outermost 'atomic' block should commit on exit,
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# ie. if autocommit was active on entry.
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self.commit_on_exit = True
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# Tracks if the transaction should be rolled back to the next
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# available savepoint because of an exception in an inner block.
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self.needs_rollback = False
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# Connection termination related attributes
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self.close_at = None
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self.errors_occurred = False
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# Thread-safety related attributes
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self.allow_thread_sharing = allow_thread_sharing
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self._thread_ident = thread.get_ident()
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def __eq__(self, other):
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if isinstance(other, BaseDatabaseWrapper):
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return self.alias == other.alias
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return NotImplemented
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def __ne__(self, other):
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return not self == other
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def __hash__(self):
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return hash(self.alias)
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##### Backend-specific methods for creating connections and cursors #####
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def get_connection_params(self):
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"""Returns a dict of parameters suitable for get_new_connection."""
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raise NotImplementedError
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def get_new_connection(self, conn_params):
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"""Opens a connection to the database."""
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raise NotImplementedError
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def init_connection_state(self):
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"""Initializes the database connection settings."""
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raise NotImplementedError
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def create_cursor(self):
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"""Creates a cursor. Assumes that a connection is established."""
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raise NotImplementedError
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##### Backend-specific methods for creating connections #####
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def connect(self):
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"""Connects to the database. Assumes that the connection is closed."""
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# In case the previous connection was closed while in an atomic block
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self.in_atomic_block = False
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self.savepoint_ids = []
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# Reset parameters defining when to close the connection
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max_age = self.settings_dict['CONN_MAX_AGE']
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self.close_at = None if max_age is None else time.time() + max_age
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self.errors_occurred = False
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# Establish the connection
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conn_params = self.get_connection_params()
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self.connection = self.get_new_connection(conn_params)
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self.init_connection_state()
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if self.settings_dict['AUTOCOMMIT']:
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self.set_autocommit(True)
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connection_created.send(sender=self.__class__, connection=self)
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def ensure_connection(self):
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"""
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Guarantees that a connection to the database is established.
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"""
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if self.connection is None:
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with self.wrap_database_errors():
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self.connect()
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##### Backend-specific wrappers for PEP-249 connection methods #####
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def _cursor(self):
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self.ensure_connection()
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with self.wrap_database_errors():
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return self.create_cursor()
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def _commit(self):
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if self.connection is not None:
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with self.wrap_database_errors():
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return self.connection.commit()
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def _rollback(self):
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if self.connection is not None:
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with self.wrap_database_errors():
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return self.connection.rollback()
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def _close(self):
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if self.connection is not None:
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with self.wrap_database_errors():
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return self.connection.close()
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##### Generic wrappers for PEP-249 connection methods #####
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def cursor(self):
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"""
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Creates a cursor, opening a connection if necessary.
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"""
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self.validate_thread_sharing()
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if (self.use_debug_cursor or
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(self.use_debug_cursor is None and settings.DEBUG)):
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cursor = self.make_debug_cursor(self._cursor())
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else:
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cursor = util.CursorWrapper(self._cursor(), self)
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return cursor
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def commit(self):
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"""
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Commits a transaction and resets the dirty flag.
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"""
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self.validate_thread_sharing()
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self.validate_no_atomic_block()
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self._commit()
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self.set_clean()
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def rollback(self):
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"""
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Rolls back a transaction and resets the dirty flag.
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"""
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self.validate_thread_sharing()
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self.validate_no_atomic_block()
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self._rollback()
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self.set_clean()
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def close(self):
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"""
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Closes the connection to the database.
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"""
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self.validate_thread_sharing()
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# Don't call validate_no_atomic_block() to avoid making it difficult
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# to get rid of a connection in an invalid state. The next connect()
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# will reset the transaction state anyway.
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try:
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self._close()
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finally:
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self.connection = None
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self.set_clean()
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##### Backend-specific savepoint management methods #####
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def _savepoint(self, sid):
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self.cursor().execute(self.ops.savepoint_create_sql(sid))
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def _savepoint_rollback(self, sid):
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self.cursor().execute(self.ops.savepoint_rollback_sql(sid))
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def _savepoint_commit(self, sid):
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self.cursor().execute(self.ops.savepoint_commit_sql(sid))
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def _savepoint_allowed(self):
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# Savepoints cannot be created outside a transaction
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return self.features.uses_savepoints and not self.get_autocommit()
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##### Generic savepoint management methods #####
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def savepoint(self):
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"""
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Creates a savepoint inside the current transaction. Returns an
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identifier for the savepoint that will be used for the subsequent
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rollback or commit. Does nothing if savepoints are not supported.
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"""
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if not self._savepoint_allowed():
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return
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thread_ident = thread.get_ident()
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tid = str(thread_ident).replace('-', '')
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self.savepoint_state += 1
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sid = "s%s_x%d" % (tid, self.savepoint_state)
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self.validate_thread_sharing()
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self._savepoint(sid)
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return sid
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def savepoint_rollback(self, sid):
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"""
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Rolls back to a savepoint. Does nothing if savepoints are not supported.
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"""
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if not self._savepoint_allowed():
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return
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self.validate_thread_sharing()
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self._savepoint_rollback(sid)
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def savepoint_commit(self, sid):
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"""
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Releases a savepoint. Does nothing if savepoints are not supported.
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"""
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if not self._savepoint_allowed():
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return
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self.validate_thread_sharing()
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self._savepoint_commit(sid)
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def clean_savepoints(self):
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"""
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Resets the counter used to generate unique savepoint ids in this thread.
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"""
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self.savepoint_state = 0
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##### Backend-specific transaction management methods #####
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def _set_autocommit(self, autocommit):
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"""
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Backend-specific implementation to enable or disable autocommit.
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"""
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raise NotImplementedError
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##### Generic transaction management methods #####
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def enter_transaction_management(self, managed=True, forced=False):
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"""
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Enters transaction management for a running thread. It must be balanced with
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the appropriate leave_transaction_management call, since the actual state is
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managed as a stack.
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The state and dirty flag are carried over from the surrounding block or
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from the settings, if there is no surrounding block (dirty is always false
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when no current block is running).
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If you switch off transaction management and there is a pending
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commit/rollback, the data will be commited, unless "forced" is True.
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"""
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self.validate_no_atomic_block()
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self.transaction_state.append(managed)
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if not managed and self.is_dirty() and not forced:
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self.commit()
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self.set_clean()
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if managed == self.get_autocommit():
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self.set_autocommit(not managed)
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def leave_transaction_management(self):
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"""
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Leaves transaction management for a running thread. A dirty flag is carried
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over to the surrounding block, as a commit will commit all changes, even
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those from outside. (Commits are on connection level.)
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"""
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self.validate_no_atomic_block()
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if self.transaction_state:
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del self.transaction_state[-1]
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else:
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raise TransactionManagementError(
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"This code isn't under transaction management")
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if self.transaction_state:
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managed = self.transaction_state[-1]
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else:
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managed = not self.settings_dict['AUTOCOMMIT']
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if self._dirty:
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self.rollback()
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if managed == self.get_autocommit():
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self.set_autocommit(not managed)
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raise TransactionManagementError(
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"Transaction managed block ended with pending COMMIT/ROLLBACK")
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if managed == self.get_autocommit():
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self.set_autocommit(not managed)
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def get_autocommit(self):
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"""
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Check the autocommit state.
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"""
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self.ensure_connection()
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return self.autocommit
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def set_autocommit(self, autocommit):
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"""
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Enable or disable autocommit.
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"""
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self.validate_no_atomic_block()
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self.ensure_connection()
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self._set_autocommit(autocommit)
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self.autocommit = autocommit
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def get_rollback(self):
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"""
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Get the "needs rollback" flag -- for *advanced use* only.
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"""
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if not self.in_atomic_block:
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raise TransactionManagementError(
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"The rollback flag doesn't work outside of an 'atomic' block.")
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return self.needs_rollback
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def set_rollback(self, rollback):
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"""
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Set or unset the "needs rollback" flag -- for *advanced use* only.
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"""
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if not self.in_atomic_block:
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raise TransactionManagementError(
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"The rollback flag doesn't work outside of an 'atomic' block.")
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self.needs_rollback = rollback
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def validate_no_atomic_block(self):
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"""
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Raise an error if an atomic block is active.
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"""
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if self.in_atomic_block:
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raise TransactionManagementError(
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"This is forbidden when an 'atomic' block is active.")
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def abort(self):
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"""
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Roll back any ongoing transaction and clean the transaction state
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stack.
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"""
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if self._dirty:
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self.rollback()
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while self.transaction_state:
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self.leave_transaction_management()
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def is_dirty(self):
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"""
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Returns True if the current transaction requires a commit for changes to
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happen.
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"""
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return self._dirty
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def set_dirty(self):
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"""
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Sets a dirty flag for the current thread and code streak. This can be used
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to decide in a managed block of code to decide whether there are open
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changes waiting for commit.
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"""
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if not self.get_autocommit():
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self._dirty = True
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def set_clean(self):
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"""
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Resets a dirty flag for the current thread and code streak. This can be used
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to decide in a managed block of code to decide whether a commit or rollback
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should happen.
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"""
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self._dirty = False
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self.clean_savepoints()
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##### Foreign key constraints checks handling #####
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@contextmanager
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def constraint_checks_disabled(self):
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"""
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Context manager that disables foreign key constraint checking.
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"""
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disabled = self.disable_constraint_checking()
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try:
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yield
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finally:
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if disabled:
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self.enable_constraint_checking()
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def disable_constraint_checking(self):
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"""
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Backends can implement as needed to temporarily disable foreign key
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constraint checking. Should return True if the constraints were
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disabled and will need to be reenabled.
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"""
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return False
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def enable_constraint_checking(self):
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"""
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Backends can implement as needed to re-enable foreign key constraint
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checking.
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"""
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pass
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def check_constraints(self, table_names=None):
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"""
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Backends can override this method if they can apply constraint
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checking (e.g. via "SET CONSTRAINTS ALL IMMEDIATE"). Should raise an
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IntegrityError if any invalid foreign key references are encountered.
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"""
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pass
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##### Connection termination handling #####
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def is_usable(self):
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"""
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Tests if the database connection is usable.
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This function may assume that self.connection is not None.
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"""
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raise NotImplementedError
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def close_if_unusable_or_obsolete(self):
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"""
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Closes the current connection if unrecoverable errors have occurred,
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or if it outlived its maximum age.
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"""
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if self.connection is not None:
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# If the application didn't restore the original autocommit setting,
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# don't take chances, drop the connection.
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if self.get_autocommit() != self.settings_dict['AUTOCOMMIT']:
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self.close()
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return
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if self.errors_occurred:
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if self.is_usable():
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self.errors_occurred = False
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else:
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self.close()
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return
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if self.close_at is not None and time.time() >= self.close_at:
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self.close()
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return
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|
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##### Thread safety handling #####
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def validate_thread_sharing(self):
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"""
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Validates that the connection isn't accessed by another thread than the
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one which originally created it, unless the connection was explicitly
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authorized to be shared between threads (via the `allow_thread_sharing`
|
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property). Raises an exception if the validation fails.
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"""
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if not (self.allow_thread_sharing
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or self._thread_ident == thread.get_ident()):
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raise DatabaseError("DatabaseWrapper objects created in a "
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"thread can only be used in that same thread. The object "
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"with alias '%s' was created in thread id %s and this is "
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"thread id %s."
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% (self.alias, self._thread_ident, thread.get_ident()))
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##### Miscellaneous #####
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def wrap_database_errors(self):
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"""
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Context manager and decorator that re-throws backend-specific database
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exceptions using Django's common wrappers.
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"""
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return DatabaseErrorWrapper(self)
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|
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def make_debug_cursor(self, cursor):
|
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"""
|
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Creates a cursor that logs all queries in self.queries.
|
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"""
|
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return util.CursorDebugWrapper(cursor, self)
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|
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@contextmanager
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def temporary_connection(self):
|
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"""
|
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Context manager that ensures that a connection is established, and
|
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if it opened one, closes it to avoid leaving a dangling connection.
|
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This is useful for operations outside of the request-response cycle.
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Provides a cursor: with self.temporary_connection() as cursor: ...
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"""
|
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must_close = self.connection is None
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cursor = self.cursor()
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try:
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yield cursor
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finally:
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cursor.close()
|
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if must_close:
|
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self.close()
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|
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def _start_transaction_under_autocommit(self):
|
|
"""
|
|
Only required when autocommits_when_autocommit_is_off = True.
|
|
"""
|
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raise NotImplementedError
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|
|
def schema_editor(self, *args, **kwargs):
|
|
"Returns a new instance of this backend's SchemaEditor"
|
|
raise NotImplementedError()
|
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|
|
|
|
class BaseDatabaseFeatures(object):
|
|
allows_group_by_pk = False
|
|
# True if django.db.backend.utils.typecast_timestamp is used on values
|
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# returned from dates() calls.
|
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needs_datetime_string_cast = True
|
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empty_fetchmany_value = []
|
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update_can_self_select = True
|
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|
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# Does the backend distinguish between '' and None?
|
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interprets_empty_strings_as_nulls = False
|
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|
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# Does the backend allow inserting duplicate rows when a unique_together
|
|
# constraint exists, but one of the unique_together columns is NULL?
|
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ignores_nulls_in_unique_constraints = True
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|
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can_use_chunked_reads = True
|
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can_return_id_from_insert = False
|
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has_bulk_insert = False
|
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uses_savepoints = False
|
|
can_combine_inserts_with_and_without_auto_increment_pk = False
|
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|
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# If True, don't use integer foreign keys referring to, e.g., positive
|
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# integer primary keys.
|
|
related_fields_match_type = False
|
|
allow_sliced_subqueries = True
|
|
has_select_for_update = False
|
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has_select_for_update_nowait = False
|
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|
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supports_select_related = True
|
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|
|
# Does the default test database allow multiple connections?
|
|
# Usually an indication that the test database is in-memory
|
|
test_db_allows_multiple_connections = True
|
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|
|
# Can an object be saved without an explicit primary key?
|
|
supports_unspecified_pk = False
|
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|
|
# Can a fixture contain forward references? i.e., are
|
|
# FK constraints checked at the end of transaction, or
|
|
# at the end of each save operation?
|
|
supports_forward_references = True
|
|
|
|
# Does a dirty transaction need to be rolled back
|
|
# before the cursor can be used again?
|
|
requires_rollback_on_dirty_transaction = False
|
|
|
|
# Does the backend allow very long model names without error?
|
|
supports_long_model_names = True
|
|
|
|
# Is there a REAL datatype in addition to floats/doubles?
|
|
has_real_datatype = False
|
|
supports_subqueries_in_group_by = True
|
|
supports_bitwise_or = True
|
|
|
|
# Do time/datetime fields have microsecond precision?
|
|
supports_microsecond_precision = True
|
|
|
|
# Does the __regex lookup support backreferencing and grouping?
|
|
supports_regex_backreferencing = True
|
|
|
|
# Can date/datetime lookups be performed using a string?
|
|
supports_date_lookup_using_string = True
|
|
|
|
# Can datetimes with timezones be used?
|
|
supports_timezones = True
|
|
|
|
# Does the database have a copy of the zoneinfo database?
|
|
has_zoneinfo_database = True
|
|
|
|
# When performing a GROUP BY, is an ORDER BY NULL required
|
|
# to remove any ordering?
|
|
requires_explicit_null_ordering_when_grouping = False
|
|
|
|
# Does the backend order NULL values as largest or smallest?
|
|
nulls_order_largest = False
|
|
|
|
# Is there a 1000 item limit on query parameters?
|
|
supports_1000_query_parameters = True
|
|
|
|
# Can an object have a primary key of 0? MySQL says No.
|
|
allows_primary_key_0 = True
|
|
|
|
# Do we need to NULL a ForeignKey out, or can the constraint check be
|
|
# deferred
|
|
can_defer_constraint_checks = False
|
|
|
|
# date_interval_sql can properly handle mixed Date/DateTime fields and timedeltas
|
|
supports_mixed_date_datetime_comparisons = True
|
|
|
|
# Does the backend support tablespaces? Default to False because it isn't
|
|
# in the SQL standard.
|
|
supports_tablespaces = False
|
|
|
|
# Does the backend reset sequences between tests?
|
|
supports_sequence_reset = True
|
|
|
|
# Confirm support for introspected foreign keys
|
|
# Every database can do this reliably, except MySQL,
|
|
# which can't do it for MyISAM tables
|
|
can_introspect_foreign_keys = True
|
|
|
|
# Support for the DISTINCT ON clause
|
|
can_distinct_on_fields = False
|
|
|
|
# Does the backend decide to commit before SAVEPOINT statements
|
|
# when autocommit is disabled? http://bugs.python.org/issue8145#msg109965
|
|
autocommits_when_autocommit_is_off = False
|
|
|
|
# Can we roll back DDL in a transaction?
|
|
can_rollback_ddl = False
|
|
|
|
# Can we issue more than one ALTER COLUMN clause in an ALTER TABLE?
|
|
supports_combined_alters = False
|
|
|
|
# What's the maximum length for index names?
|
|
max_index_name_length = 63
|
|
|
|
# Does it support foreign keys?
|
|
supports_foreign_keys = True
|
|
|
|
# Does it support CHECK constraints?
|
|
supports_check_constraints = True
|
|
|
|
# Does the backend support 'pyformat' style ("... %(name)s ...", {'name': value})
|
|
# parameter passing? Note this can be provided by the backend even if not
|
|
# supported by the Python driver
|
|
supports_paramstyle_pyformat = True
|
|
|
|
# Does the backend require literal defaults, rather than parameterised ones?
|
|
requires_literal_defaults = False
|
|
|
|
# Does the backend require a connection reset after each material schema change?
|
|
connection_persists_old_columns = False
|
|
|
|
def __init__(self, connection):
|
|
self.connection = connection
|
|
|
|
@cached_property
|
|
def supports_transactions(self):
|
|
"Confirm support for transactions"
|
|
try:
|
|
# Make sure to run inside a managed transaction block,
|
|
# otherwise autocommit will cause the confimation to
|
|
# fail.
|
|
self.connection.enter_transaction_management()
|
|
cursor = self.connection.cursor()
|
|
cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
|
|
self.connection.commit()
|
|
cursor.execute('INSERT INTO ROLLBACK_TEST (X) VALUES (8)')
|
|
self.connection.rollback()
|
|
cursor.execute('SELECT COUNT(X) FROM ROLLBACK_TEST')
|
|
count, = cursor.fetchone()
|
|
cursor.execute('DROP TABLE ROLLBACK_TEST')
|
|
self.connection.commit()
|
|
finally:
|
|
self.connection.leave_transaction_management()
|
|
return count == 0
|
|
|
|
@cached_property
|
|
def supports_stddev(self):
|
|
"Confirm support for STDDEV and related stats functions"
|
|
class StdDevPop(object):
|
|
sql_function = 'STDDEV_POP'
|
|
|
|
try:
|
|
self.connection.ops.check_aggregate_support(StdDevPop())
|
|
return True
|
|
except NotImplementedError:
|
|
return False
|
|
|
|
|
|
class BaseDatabaseOperations(object):
|
|
"""
|
|
This class encapsulates all backend-specific differences, such as the way
|
|
a backend performs ordering or calculates the ID of a recently-inserted
|
|
row.
|
|
"""
|
|
compiler_module = "django.db.models.sql.compiler"
|
|
|
|
def __init__(self, connection):
|
|
self.connection = connection
|
|
self._cache = None
|
|
|
|
def autoinc_sql(self, table, column):
|
|
"""
|
|
Returns any SQL needed to support auto-incrementing primary keys, or
|
|
None if no SQL is necessary.
|
|
|
|
This SQL is executed when a table is created.
|
|
"""
|
|
return None
|
|
|
|
def bulk_batch_size(self, fields, objs):
|
|
"""
|
|
Returns the maximum allowed batch size for the backend. The fields
|
|
are the fields going to be inserted in the batch, the objs contains
|
|
all the objects to be inserted.
|
|
"""
|
|
return len(objs)
|
|
|
|
def cache_key_culling_sql(self):
|
|
"""
|
|
Returns an SQL query that retrieves the first cache key greater than the
|
|
n smallest.
|
|
|
|
This is used by the 'db' cache backend to determine where to start
|
|
culling.
|
|
"""
|
|
return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"
|
|
|
|
def date_extract_sql(self, lookup_type, field_name):
|
|
"""
|
|
Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
|
|
extracts a value from the given date field field_name.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def date_interval_sql(self, sql, connector, timedelta):
|
|
"""
|
|
Implements the date interval functionality for expressions
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def date_trunc_sql(self, lookup_type, field_name):
|
|
"""
|
|
Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
|
|
truncates the given date field field_name to a date object with only
|
|
the given specificity.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def datetime_cast_sql(self):
|
|
"""
|
|
Returns the SQL necessary to cast a datetime value so that it will be
|
|
retrieved as a Python datetime object instead of a string.
|
|
|
|
This SQL should include a '%s' in place of the field's name.
|
|
"""
|
|
return "%s"
|
|
|
|
def datetime_extract_sql(self, lookup_type, field_name, tzname):
|
|
"""
|
|
Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
|
|
'second', returns the SQL that extracts a value from the given
|
|
datetime field field_name, and a tuple of parameters.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def datetime_trunc_sql(self, lookup_type, field_name, tzname):
|
|
"""
|
|
Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
|
|
'second', returns the SQL that truncates the given datetime field
|
|
field_name to a datetime object with only the given specificity, and
|
|
a tuple of parameters.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def deferrable_sql(self):
|
|
"""
|
|
Returns the SQL necessary to make a constraint "initially deferred"
|
|
during a CREATE TABLE statement.
|
|
"""
|
|
return ''
|
|
|
|
def distinct_sql(self, fields):
|
|
"""
|
|
Returns an SQL DISTINCT clause which removes duplicate rows from the
|
|
result set. If any fields are given, only the given fields are being
|
|
checked for duplicates.
|
|
"""
|
|
if fields:
|
|
raise NotImplementedError('DISTINCT ON fields is not supported by this database backend')
|
|
else:
|
|
return 'DISTINCT'
|
|
|
|
def drop_foreignkey_sql(self):
|
|
"""
|
|
Returns the SQL command that drops a foreign key.
|
|
"""
|
|
return "DROP CONSTRAINT"
|
|
|
|
def drop_sequence_sql(self, table):
|
|
"""
|
|
Returns any SQL necessary to drop the sequence for the given table.
|
|
Returns None if no SQL is necessary.
|
|
"""
|
|
return None
|
|
|
|
def fetch_returned_insert_id(self, cursor):
|
|
"""
|
|
Given a cursor object that has just performed an INSERT...RETURNING
|
|
statement into a table that has an auto-incrementing ID, returns the
|
|
newly created ID.
|
|
"""
|
|
return cursor.fetchone()[0]
|
|
|
|
def field_cast_sql(self, db_type, internal_type):
|
|
"""
|
|
Given a column type (e.g. 'BLOB', 'VARCHAR'), and an internal type
|
|
(e.g. 'GenericIPAddressField'), returns the SQL necessary to cast it
|
|
before using it in a WHERE statement. Note that the resulting string
|
|
should contain a '%s' placeholder for the column being searched against.
|
|
"""
|
|
return '%s'
|
|
|
|
def force_no_ordering(self):
|
|
"""
|
|
Returns a list used in the "ORDER BY" clause to force no ordering at
|
|
all. Returning an empty list means that nothing will be included in the
|
|
ordering.
|
|
"""
|
|
return []
|
|
|
|
def for_update_sql(self, nowait=False):
|
|
"""
|
|
Returns the FOR UPDATE SQL clause to lock rows for an update operation.
|
|
"""
|
|
if nowait:
|
|
return 'FOR UPDATE NOWAIT'
|
|
else:
|
|
return 'FOR UPDATE'
|
|
|
|
def fulltext_search_sql(self, field_name):
|
|
"""
|
|
Returns the SQL WHERE clause to use in order to perform a full-text
|
|
search of the given field_name. Note that the resulting string should
|
|
contain a '%s' placeholder for the value being searched against.
|
|
"""
|
|
raise NotImplementedError('Full-text search is not implemented for this database backend')
|
|
|
|
def last_executed_query(self, cursor, sql, params):
|
|
"""
|
|
Returns a string of the query last executed by the given cursor, with
|
|
placeholders replaced with actual values.
|
|
|
|
`sql` is the raw query containing placeholders, and `params` is the
|
|
sequence of parameters. These are used by default, but this method
|
|
exists for database backends to provide a better implementation
|
|
according to their own quoting schemes.
|
|
"""
|
|
from django.utils.encoding import force_text
|
|
|
|
# Convert params to contain Unicode values.
|
|
to_unicode = lambda s: force_text(s, strings_only=True, errors='replace')
|
|
if isinstance(params, (list, tuple)):
|
|
u_params = tuple(to_unicode(val) for val in params)
|
|
elif params is None:
|
|
u_params = ()
|
|
else:
|
|
u_params = dict((to_unicode(k), to_unicode(v)) for k, v in params.items())
|
|
|
|
return six.text_type("QUERY = %r - PARAMS = %r") % (sql, u_params)
|
|
|
|
def last_insert_id(self, cursor, table_name, pk_name):
|
|
"""
|
|
Given a cursor object that has just performed an INSERT statement into
|
|
a table that has an auto-incrementing ID, returns the newly created ID.
|
|
|
|
This method also receives the table name and the name of the primary-key
|
|
column.
|
|
"""
|
|
return cursor.lastrowid
|
|
|
|
def lookup_cast(self, lookup_type):
|
|
"""
|
|
Returns the string to use in a query when performing lookups
|
|
("contains", "like", etc). The resulting string should contain a '%s'
|
|
placeholder for the column being searched against.
|
|
"""
|
|
return "%s"
|
|
|
|
def max_in_list_size(self):
|
|
"""
|
|
Returns the maximum number of items that can be passed in a single 'IN'
|
|
list condition, or None if the backend does not impose a limit.
|
|
"""
|
|
return None
|
|
|
|
def max_name_length(self):
|
|
"""
|
|
Returns the maximum length of table and column names, or None if there
|
|
is no limit.
|
|
"""
|
|
return None
|
|
|
|
def no_limit_value(self):
|
|
"""
|
|
Returns the value to use for the LIMIT when we are wanting "LIMIT
|
|
infinity". Returns None if the limit clause can be omitted in this case.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def pk_default_value(self):
|
|
"""
|
|
Returns the value to use during an INSERT statement to specify that
|
|
the field should use its default value.
|
|
"""
|
|
return 'DEFAULT'
|
|
|
|
def process_clob(self, value):
|
|
"""
|
|
Returns the value of a CLOB column, for backends that return a locator
|
|
object that requires additional processing.
|
|
"""
|
|
return value
|
|
|
|
def return_insert_id(self):
|
|
"""
|
|
For backends that support returning the last insert ID as part
|
|
of an insert query, this method returns the SQL and params to
|
|
append to the INSERT query. The returned fragment should
|
|
contain a format string to hold the appropriate column.
|
|
"""
|
|
pass
|
|
|
|
def compiler(self, compiler_name):
|
|
"""
|
|
Returns the SQLCompiler class corresponding to the given name,
|
|
in the namespace corresponding to the `compiler_module` attribute
|
|
on this backend.
|
|
"""
|
|
if self._cache is None:
|
|
self._cache = import_module(self.compiler_module)
|
|
return getattr(self._cache, compiler_name)
|
|
|
|
def quote_name(self, name):
|
|
"""
|
|
Returns a quoted version of the given table, index or column name. Does
|
|
not quote the given name if it's already been quoted.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def quote_parameter(self, value):
|
|
"""
|
|
Returns a quoted version of the value so it's safe to use in an SQL
|
|
string. This should NOT be used to prepare SQL statements to send to
|
|
the database; it is meant for outputting SQL statements to a file
|
|
or the console for later execution by a developer/DBA.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def random_function_sql(self):
|
|
"""
|
|
Returns an SQL expression that returns a random value.
|
|
"""
|
|
return 'RANDOM()'
|
|
|
|
def regex_lookup(self, lookup_type):
|
|
"""
|
|
Returns the string to use in a query when performing regular expression
|
|
lookups (using "regex" or "iregex"). The resulting string should
|
|
contain a '%s' placeholder for the column being searched against.
|
|
|
|
If the feature is not supported (or part of it is not supported), a
|
|
NotImplementedError exception can be raised.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def savepoint_create_sql(self, sid):
|
|
"""
|
|
Returns the SQL for starting a new savepoint. Only required if the
|
|
"uses_savepoints" feature is True. The "sid" parameter is a string
|
|
for the savepoint id.
|
|
"""
|
|
return "SAVEPOINT %s" % self.quote_name(sid)
|
|
|
|
def savepoint_commit_sql(self, sid):
|
|
"""
|
|
Returns the SQL for committing the given savepoint.
|
|
"""
|
|
return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
|
|
|
|
def savepoint_rollback_sql(self, sid):
|
|
"""
|
|
Returns the SQL for rolling back the given savepoint.
|
|
"""
|
|
return "ROLLBACK TO SAVEPOINT %s" % self.quote_name(sid)
|
|
|
|
def set_time_zone_sql(self):
|
|
"""
|
|
Returns the SQL that will set the connection's time zone.
|
|
|
|
Returns '' if the backend doesn't support time zones.
|
|
"""
|
|
return ''
|
|
|
|
def sql_flush(self, style, tables, sequences, allow_cascade=False):
|
|
"""
|
|
Returns a list of SQL statements required to remove all data from
|
|
the given database tables (without actually removing the tables
|
|
themselves).
|
|
|
|
The returned value also includes SQL statements required to reset DB
|
|
sequences passed in :param sequences:.
|
|
|
|
The `style` argument is a Style object as returned by either
|
|
color_style() or no_style() in django.core.management.color.
|
|
|
|
The `allow_cascade` argument determines whether truncation may cascade
|
|
to tables with foreign keys pointing the tables being truncated.
|
|
PostgreSQL requires a cascade even if these tables are empty.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def sequence_reset_by_name_sql(self, style, sequences):
|
|
"""
|
|
Returns a list of the SQL statements required to reset sequences
|
|
passed in :param sequences:.
|
|
|
|
The `style` argument is a Style object as returned by either
|
|
color_style() or no_style() in django.core.management.color.
|
|
"""
|
|
return []
|
|
|
|
def sequence_reset_sql(self, style, model_list):
|
|
"""
|
|
Returns a list of the SQL statements required to reset sequences for
|
|
the given models.
|
|
|
|
The `style` argument is a Style object as returned by either
|
|
color_style() or no_style() in django.core.management.color.
|
|
"""
|
|
return [] # No sequence reset required by default.
|
|
|
|
def start_transaction_sql(self):
|
|
"""
|
|
Returns the SQL statement required to start a transaction.
|
|
"""
|
|
return "BEGIN;"
|
|
|
|
def end_transaction_sql(self, success=True):
|
|
"""
|
|
Returns the SQL statement required to end a transaction.
|
|
"""
|
|
if not success:
|
|
return "ROLLBACK;"
|
|
return "COMMIT;"
|
|
|
|
def tablespace_sql(self, tablespace, inline=False):
|
|
"""
|
|
Returns the SQL that will be used in a query to define the tablespace.
|
|
|
|
Returns '' if the backend doesn't support tablespaces.
|
|
|
|
If inline is True, the SQL is appended to a row; otherwise it's appended
|
|
to the entire CREATE TABLE or CREATE INDEX statement.
|
|
"""
|
|
return ''
|
|
|
|
def prep_for_like_query(self, x):
|
|
"""Prepares a value for use in a LIKE query."""
|
|
from django.utils.encoding import force_text
|
|
return force_text(x).replace("\\", "\\\\").replace("%", "\%").replace("_", "\_")
|
|
|
|
# Same as prep_for_like_query(), but called for "iexact" matches, which
|
|
# need not necessarily be implemented using "LIKE" in the backend.
|
|
prep_for_iexact_query = prep_for_like_query
|
|
|
|
def validate_autopk_value(self, value):
|
|
"""
|
|
Certain backends do not accept some values for "serial" fields
|
|
(for example zero in MySQL). This method will raise a ValueError
|
|
if the value is invalid, otherwise returns validated value.
|
|
"""
|
|
return value
|
|
|
|
def value_to_db_date(self, value):
|
|
"""
|
|
Transform a date value to an object compatible with what is expected
|
|
by the backend driver for date columns.
|
|
"""
|
|
if value is None:
|
|
return None
|
|
return six.text_type(value)
|
|
|
|
def value_to_db_datetime(self, value):
|
|
"""
|
|
Transform a datetime value to an object compatible with what is expected
|
|
by the backend driver for datetime columns.
|
|
"""
|
|
if value is None:
|
|
return None
|
|
return six.text_type(value)
|
|
|
|
def value_to_db_time(self, value):
|
|
"""
|
|
Transform a time value to an object compatible with what is expected
|
|
by the backend driver for time columns.
|
|
"""
|
|
if value is None:
|
|
return None
|
|
if timezone.is_aware(value):
|
|
raise ValueError("Django does not support timezone-aware times.")
|
|
return six.text_type(value)
|
|
|
|
def value_to_db_decimal(self, value, max_digits, decimal_places):
|
|
"""
|
|
Transform a decimal.Decimal value to an object compatible with what is
|
|
expected by the backend driver for decimal (numeric) columns.
|
|
"""
|
|
if value is None:
|
|
return None
|
|
return util.format_number(value, max_digits, decimal_places)
|
|
|
|
def year_lookup_bounds_for_date_field(self, value):
|
|
"""
|
|
Returns a two-elements list with the lower and upper bound to be used
|
|
with a BETWEEN operator to query a DateField value using a year
|
|
lookup.
|
|
|
|
`value` is an int, containing the looked-up year.
|
|
"""
|
|
first = datetime.date(value, 1, 1)
|
|
second = datetime.date(value, 12, 31)
|
|
return [first, second]
|
|
|
|
def year_lookup_bounds_for_datetime_field(self, value):
|
|
"""
|
|
Returns a two-elements list with the lower and upper bound to be used
|
|
with a BETWEEN operator to query a DateTimeField value using a year
|
|
lookup.
|
|
|
|
`value` is an int, containing the looked-up year.
|
|
"""
|
|
first = datetime.datetime(value, 1, 1)
|
|
second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
|
|
if settings.USE_TZ:
|
|
tz = timezone.get_current_timezone()
|
|
first = timezone.make_aware(first, tz)
|
|
second = timezone.make_aware(second, tz)
|
|
return [first, second]
|
|
|
|
def convert_values(self, value, field):
|
|
"""
|
|
Coerce the value returned by the database backend into a consistent type
|
|
that is compatible with the field type.
|
|
"""
|
|
if value is None:
|
|
return value
|
|
internal_type = field.get_internal_type()
|
|
if internal_type == 'FloatField':
|
|
return float(value)
|
|
elif (internal_type and (internal_type.endswith('IntegerField')
|
|
or internal_type == 'AutoField')):
|
|
return int(value)
|
|
return value
|
|
|
|
def check_aggregate_support(self, aggregate_func):
|
|
"""Check that the backend supports the provided aggregate
|
|
|
|
This is used on specific backends to rule out known aggregates
|
|
that are known to have faulty implementations. If the named
|
|
aggregate function has a known problem, the backend should
|
|
raise NotImplementedError.
|
|
"""
|
|
pass
|
|
|
|
def combine_expression(self, connector, sub_expressions):
|
|
"""Combine a list of subexpressions into a single expression, using
|
|
the provided connecting operator. This is required because operators
|
|
can vary between backends (e.g., Oracle with %% and &) and between
|
|
subexpression types (e.g., date expressions)
|
|
"""
|
|
conn = ' %s ' % connector
|
|
return conn.join(sub_expressions)
|
|
|
|
def modify_insert_params(self, placeholders, params):
|
|
"""Allow modification of insert parameters. Needed for Oracle Spatial
|
|
backend due to #10888.
|
|
"""
|
|
return params
|
|
|
|
|
|
# Structure returned by the DB-API cursor.description interface (PEP 249)
|
|
FieldInfo = namedtuple('FieldInfo',
|
|
'name type_code display_size internal_size precision scale null_ok'
|
|
)
|
|
|
|
|
|
class BaseDatabaseIntrospection(object):
|
|
"""
|
|
This class encapsulates all backend-specific introspection utilities
|
|
"""
|
|
data_types_reverse = {}
|
|
|
|
def __init__(self, connection):
|
|
self.connection = connection
|
|
|
|
def get_field_type(self, data_type, description):
|
|
"""Hook for a database backend to use the cursor description to
|
|
match a Django field type to a database column.
|
|
|
|
For Oracle, the column data_type on its own is insufficient to
|
|
distinguish between a FloatField and IntegerField, for example."""
|
|
return self.data_types_reverse[data_type]
|
|
|
|
def table_name_converter(self, name):
|
|
"""Apply a conversion to the name for the purposes of comparison.
|
|
|
|
The default table name converter is for case sensitive comparison.
|
|
"""
|
|
return name
|
|
|
|
def table_names(self, cursor=None):
|
|
"""
|
|
Returns a list of names of all tables that exist in the database.
|
|
The returned table list is sorted by Python's default sorting. We
|
|
do NOT use database's ORDER BY here to avoid subtle differences
|
|
in sorting order between databases.
|
|
"""
|
|
if cursor is None:
|
|
cursor = self.connection.cursor()
|
|
return sorted(self.get_table_list(cursor))
|
|
|
|
def get_table_list(self, cursor):
|
|
"""
|
|
Returns an unsorted list of names of all tables that exist in the
|
|
database.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def django_table_names(self, only_existing=False):
|
|
"""
|
|
Returns a list of all table names that have associated Django models and
|
|
are in INSTALLED_APPS.
|
|
|
|
If only_existing is True, the resulting list will only include the tables
|
|
that actually exist in the database.
|
|
"""
|
|
from django.db import models, router
|
|
tables = set()
|
|
for app in models.get_apps():
|
|
for model in models.get_models(app):
|
|
if not model._meta.managed:
|
|
continue
|
|
if not router.allow_migrate(self.connection.alias, model):
|
|
continue
|
|
tables.add(model._meta.db_table)
|
|
tables.update(f.m2m_db_table() for f in model._meta.local_many_to_many)
|
|
tables = list(tables)
|
|
if only_existing:
|
|
existing_tables = self.table_names()
|
|
tables = [
|
|
t
|
|
for t in tables
|
|
if self.table_name_converter(t) in existing_tables
|
|
]
|
|
return tables
|
|
|
|
def installed_models(self, tables):
|
|
"Returns a set of all models represented by the provided list of table names."
|
|
from django.db import models, router
|
|
all_models = []
|
|
for app in models.get_apps():
|
|
for model in models.get_models(app):
|
|
if router.allow_migrate(self.connection.alias, model):
|
|
all_models.append(model)
|
|
tables = list(map(self.table_name_converter, tables))
|
|
return set([
|
|
m for m in all_models
|
|
if self.table_name_converter(m._meta.db_table) in tables
|
|
])
|
|
|
|
def sequence_list(self):
|
|
"Returns a list of information about all DB sequences for all models in all apps."
|
|
from django.db import models, router
|
|
|
|
apps = models.get_apps()
|
|
sequence_list = []
|
|
|
|
for app in apps:
|
|
for model in models.get_models(app):
|
|
if not model._meta.managed:
|
|
continue
|
|
if model._meta.swapped:
|
|
continue
|
|
if not router.allow_migrate(self.connection.alias, model):
|
|
continue
|
|
for f in model._meta.local_fields:
|
|
if isinstance(f, models.AutoField):
|
|
sequence_list.append({'table': model._meta.db_table, 'column': f.column})
|
|
break # Only one AutoField is allowed per model, so don't bother continuing.
|
|
|
|
for f in model._meta.local_many_to_many:
|
|
# If this is an m2m using an intermediate table,
|
|
# we don't need to reset the sequence.
|
|
if f.rel.through is None:
|
|
sequence_list.append({'table': f.m2m_db_table(), 'column': None})
|
|
|
|
return sequence_list
|
|
|
|
def get_key_columns(self, cursor, table_name):
|
|
"""
|
|
Backends can override this to return a list of (column_name, referenced_table_name,
|
|
referenced_column_name) for all key columns in given table.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def get_primary_key_column(self, cursor, table_name):
|
|
"""
|
|
Returns the name of the primary key column for the given table.
|
|
"""
|
|
for column in six.iteritems(self.get_indexes(cursor, table_name)):
|
|
if column[1]['primary_key']:
|
|
return column[0]
|
|
return None
|
|
|
|
def get_indexes(self, cursor, table_name):
|
|
"""
|
|
Returns a dictionary of indexed fieldname -> infodict for the given
|
|
table, where each infodict is in the format:
|
|
{'primary_key': boolean representing whether it's the primary key,
|
|
'unique': boolean representing whether it's a unique index}
|
|
|
|
Only single-column indexes are introspected.
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def get_constraints(self, cursor, table_name):
|
|
"""
|
|
Retrieves any constraints or keys (unique, pk, fk, check, index)
|
|
across one or more columns.
|
|
|
|
Returns a dict mapping constraint names to their attributes,
|
|
where attributes is a dict with keys:
|
|
* columns: List of columns this covers
|
|
* primary_key: True if primary key, False otherwise
|
|
* unique: True if this is a unique constraint, False otherwise
|
|
* foreign_key: (table, column) of target, or None
|
|
* check: True if check constraint, False otherwise
|
|
* index: True if index, False otherwise.
|
|
|
|
Some backends may return special constraint names that don't exist
|
|
if they don't name constraints of a certain type (e.g. SQLite)
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
|
|
class BaseDatabaseClient(object):
|
|
"""
|
|
This class encapsulates all backend-specific methods for opening a
|
|
client shell.
|
|
"""
|
|
# This should be a string representing the name of the executable
|
|
# (e.g., "psql"). Subclasses must override this.
|
|
executable_name = None
|
|
|
|
def __init__(self, connection):
|
|
# connection is an instance of BaseDatabaseWrapper.
|
|
self.connection = connection
|
|
|
|
def runshell(self):
|
|
raise NotImplementedError()
|
|
|
|
|
|
class BaseDatabaseValidation(object):
|
|
"""
|
|
This class encapsualtes all backend-specific model validation.
|
|
"""
|
|
def __init__(self, connection):
|
|
self.connection = connection
|
|
|
|
def validate_field(self, errors, opts, f):
|
|
"By default, there is no backend-specific validation"
|
|
pass
|