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cursors.py
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import re import warnings from . import err #: Regular expression for :meth:`Cursor.executemany`. #: executemany only supports simple bulk insert. #: You can use it to load large dataset. RE_INSERT_VALUES = re.compile( r"\s*((?:INSERT|REPLACE)\b.+\bVALUES?\s*)" + r"(\(\s*(?:%s|%\(.+\)s)\s*(?:,\s*(?:%s|%\(.+\)s)\s*)*\))" + r"(\s*(?:ON DUPLICATE.*)?);?\s*\Z", re.IGNORECASE | re.DOTALL, ) class Cursor: """ This is the object used to interact with the database. Do not create an instance of a Cursor yourself. Call connections.Connection.cursor(). See `Cursor <https://www.python.org/dev/peps/pep-0249/#cursor-objects>`_ in the specification. """ #: Max statement size which :meth:`executemany` generates. #: #: Max size of allowed statement is max_allowed_packet - packet_header_size. #: Default value of max_allowed_packet is 1048576. max_stmt_length = 1024000 def __init__(self, connection): self.connection = connection self.warning_count = 0 self.description = None self.rownumber = 0 self.rowcount = -1 self.arraysize = 1 self._executed = None self._result = None self._rows = None def close(self): """ Closing a cursor just exhausts all remaining data. """ conn = self.connection if conn is None: return try: while self.nextset(): pass finally: self.connection = None def __enter__(self): return self def __exit__(self, *exc_info): del exc_info self.close() def _get_db(self): if not self.connection: raise err.ProgrammingError("Cursor closed") return self.connection def _check_executed(self): if not self._executed: raise err.ProgrammingError("execute() first") def _conv_row(self, row): return row def setinputsizes(self, *args): """Does nothing, required by DB API.""" def setoutputsizes(self, *args): """Does nothing, required by DB API.""" def _nextset(self, unbuffered=False): """Get the next query set.""" conn = self._get_db() current_result = self._result if current_result is None or current_result is not conn._result: return None if not current_result.has_next: return None self._result = None self._clear_result() conn.next_result(unbuffered=unbuffered) self._do_get_result() return True def nextset(self): return self._nextset(False) def _escape_args(self, args, conn): if isinstance(args, (tuple, list)): return tuple(conn.literal(arg) for arg in args) elif isinstance(args, dict): return {key: conn.literal(val) for (key, val) in args.items()} else: # If it's not a dictionary let's try escaping it anyways. # Worst case it will throw a Value error return conn.escape(args) def mogrify(self, query, args=None): """ Returns the exact string that would be sent to the database by calling the execute() method. :param query: Query to mogrify. :type query: str :param args: Parameters used with query. (optional) :type args: tuple, list or dict :return: The query with argument binding applied. :rtype: str This method follows the extension to the DB API 2.0 followed by Psycopg. """ conn = self._get_db() if args is not None: query = query % self._escape_args(args, conn) return query def execute(self, query, args=None): """Execute a query. :param query: Query to execute. :type query: str :param args: Parameters used with query. (optional) :type args: tuple, list or dict :return: Number of affected rows. :rtype: int If args is a list or tuple, %s can be used as a placeholder in the query. If args is a dict, %(name)s can be used as a placeholder in the query. """ while self.nextset(): pass query = self.mogrify(query, args) result = self._query(query) self._executed = query return result def executemany(self, query, args): """Run several data against one query. :param query: Query to execute. :type query: str :param args: Sequence of sequences or mappings. It is used as parameter. :type args: tuple or list :return: Number of rows affected, if any. :rtype: int or None This method improves performance on multiple-row INSERT and REPLACE. Otherwise it is equivalent to looping over args with execute(). """ if not args: return m = RE_INSERT_VALUES.match(query) if m: q_prefix = m.group(1) % () q_values = m.group(2).rstrip() q_postfix = m.group(3) or "" assert q_values[0] == "(" and q_values[-1] == ")" return self._do_execute_many( q_prefix, q_values, q_postfix, args, self.max_stmt_length, self._get_db().encoding, ) self.rowcount = sum(self.execute(query, arg) for arg in args) return self.rowcount def _do_execute_many( self, prefix, values, postfix, args, max_stmt_length, encoding ): conn = self._get_db() escape = self._escape_args if isinstance(prefix, str): prefix = prefix.encode(encoding) if isinstance(postfix, str): postfix = postfix.encode(encoding) sql = bytearray(prefix) args = iter(args) v = values % escape(next(args), conn) if isinstance(v, str): v = v.encode(encoding, "surrogateescape") sql += v rows = 0 for arg in args: v = values % escape(arg, conn) if isinstance(v, str): v = v.encode(encoding, "surrogateescape") if len(sql) + len(v) + len(postfix) + 1 > max_stmt_length: rows += self.execute(sql + postfix) sql = bytearray(prefix) else: sql += b"," sql += v rows += self.execute(sql + postfix) self.rowcount = rows return rows def callproc(self, procname, args=()): """Execute stored procedure procname with args. :param procname: Name of procedure to execute on server. :type procname: str :param args: Sequence of parameters to use with procedure. :type args: tuple or list Returns the original args. Compatibility warning: PEP-249 specifies that any modified parameters must be returned. This is currently impossible as they are only available by storing them in a server variable and then retrieved by a query. Since stored procedures return zero or more result sets, there is no reliable way to get at OUT or INOUT parameters via callproc. The server variables are named @_procname_n, where procname is the parameter above and n is the position of the parameter (from zero). Once all result sets generated by the procedure have been fetched, you can issue a SELECT @_procname_0, ... query using .execute() to get any OUT or INOUT values. Compatibility warning: The act of calling a stored procedure itself creates an empty result set. This appears after any result sets generated by the procedure. This is non-standard behavior with respect to the DB-API. Be sure to use nextset() to advance through all result sets; otherwise you may get disconnected. """ conn = self._get_db() if args: fmt = f"@_{procname}_%d=%s" self._query( "SET %s" % ",".join( fmt % (index, conn.escape(arg)) for index, arg in enumerate(args) ) ) self.nextset() q = "CALL {}({})".format( procname, ",".join(["@_%s_%d" % (procname, i) for i in range(len(args))]), ) self._query(q) self._executed = q return args def fetchone(self): """Fetch the next row.""" self._check_executed() if self._rows is None or self.rownumber >= len(self._rows): return None result = self._rows[self.rownumber] self.rownumber += 1 return result def fetchmany(self, size=None): """Fetch several rows.""" self._check_executed() if self._rows is None: # Django expects () for EOF. # https://github.com/django/django/blob/0c1518ee429b01c145cf5b34eab01b0b92f8c246/django/db/backends/mysql/features.py#L8 return () end = self.rownumber + (size or self.arraysize) result = self._rows[self.rownumber : end] self.rownumber = min(end, len(self._rows)) return result def fetchall(self): """Fetch all the rows.""" self._check_executed() if self._rows is None: return [] if self.rownumber: result = self._rows[self.rownumber :] else: result = self._rows self.rownumber = len(self._rows) return result def scroll(self, value, mode="relative"): self._check_executed() if mode == "relative": r = self.rownumber + value elif mode == "absolute": r = value else: raise err.ProgrammingError("unknown scroll mode %s" % mode) if not (0 <= r < len(self._rows)): raise IndexError("out of range") self.rownumber = r def _query(self, q): conn = self._get_db() self._clear_result() conn.query(q) self._do_get_result() return self.rowcount def _clear_result(self): self.rownumber = 0 self._result = None self.rowcount = 0 self.warning_count = 0 self.description = None self.lastrowid = None self._rows = None def _do_get_result(self): conn = self._get_db() self._result = result = conn._result self.rowcount = result.affected_rows self.warning_count = result.warning_count self.description = result.description self.lastrowid = result.insert_id self._rows = result.rows def __iter__(self): return self def __next__(self): row = self.fetchone() if row is None: raise StopIteration return row def __getattr__(self, name): # DB-API 2.0 optional extension says these errors can be accessed # via Connection object. But MySQLdb had defined them on Cursor object. if name in ( "Warning", "Error", "InterfaceError", "DatabaseError", "DataError", "OperationalError", "IntegrityError", "InternalError", "ProgrammingError", "NotSupportedError", ): # Deprecated since v1.1 warnings.warn( "PyMySQL errors hould be accessed from `pymysql` package", DeprecationWarning, stacklevel=2, ) return getattr(err, name) raise AttributeError(name) class DictCursorMixin: # You can override this to use OrderedDict or other dict-like types. dict_type = dict def _do_get_result(self): super()._do_get_result() fields = [] if self.description: for f in self._result.fields: name = f.name if name in fields: name = f.table_name + "." + name fields.append(name) self._fields = fields if fields and self._rows: self._rows = [self._conv_row(r) for r in self._rows] def _conv_row(self, row): if row is None: return None return self.dict_type(zip(self._fields, row)) class DictCursor(DictCursorMixin, Cursor): """A cursor which returns results as a dictionary""" class SSCursor(Cursor): """ Unbuffered Cursor, mainly useful for queries that return a lot of data, or for connections to remote servers over a slow network. Instead of copying every row of data into a buffer, this will fetch rows as needed. The upside of this is the client uses much less memory, and rows are returned much faster when traveling over a slow network or if the result set is very big. There are limitations, though. The MySQL protocol doesn't support returning the total number of rows, so the only way to tell how many rows there are is to iterate over every row returned. Also, it currently isn't possible to scroll backwards, as only the current row is held in memory. """ def _conv_row(self, row): return row def close(self): conn = self.connection if conn is None: return if self._result is not None and self._result is conn._result: self._result._finish_unbuffered_query() try: while self.nextset(): pass finally: self.connection = None __del__ = close def _query(self, q): conn = self._get_db() self._clear_result() conn.query(q, unbuffered=True) self._do_get_result() return self.rowcount def nextset(self): return self._nextset(unbuffered=True) def read_next(self): """Read next row.""" return self._conv_row(self._result._read_rowdata_packet_unbuffered()) def fetchone(self): """Fetch next row.""" self._check_executed() row = self.read_next() if row is None: self.warning_count = self._result.warning_count return None self.rownumber += 1 return row def fetchall(self): """ Fetch all, as per MySQLdb. Pretty useless for large queries, as it is buffered. See fetchall_unbuffered(), if you want an unbuffered generator version of this method. """ return list(self.fetchall_unbuffered()) def fetchall_unbuffered(self): """ Fetch all, implemented as a generator, which isn't to standard, however, it doesn't make sense to return everything in a list, as that would use ridiculous memory for large result sets. """ return iter(self.fetchone, None) def fetchmany(self, size=None): """Fetch many.""" self._check_executed() if size is None: size = self.arraysize rows = [] for i in range(size): row = self.read_next() if row is None: self.warning_count = self._result.warning_count break rows.append(row) self.rownumber += 1 if not rows: # Django expects () for EOF. # https://github.com/django/django/blob/0c1518ee429b01c145cf5b34eab01b0b92f8c246/django/db/backends/mysql/features.py#L8 return () return rows def scroll(self, value, mode="relative"): self._check_executed() if mode == "relative": if value < 0: raise err.NotSupportedError( "Backwards scrolling not supported by this cursor" ) for _ in range(value): self.read_next() self.rownumber += value elif mode == "absolute": if value < self.rownumber: raise err.NotSupportedError( "Backwards scrolling not supported by this cursor" ) end = value - self.rownumber for _ in range(end): self.read_next() self.rownumber = value else: raise err.ProgrammingError("unknown scroll mode %s" % mode) class SSDictCursor(DictCursorMixin, SSCursor): """An unbuffered cursor, which returns results as a dictionary"""