371 lines
10 KiB
Python
371 lines
10 KiB
Python
from collections import namedtuple
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from itertools import islice
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from ..errors import Error as DriverError
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from .errors import InterfaceError, OperationalError, ProgrammingError
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Column = namedtuple(
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'Column',
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'name type_code display_size internal_size precision scale null_ok'
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)
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class Cursor(object):
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class States(object):
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(
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NONE,
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RUNNING,
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FINISHED,
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CURSOR_CLOSED
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) = range(4)
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_states = States()
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def __init__(self, client, connection):
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self._client = client
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self._connection = connection
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self._reset_state()
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self.arraysize = 1
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# Begin non-PEP attributes
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self._columns_with_types = None
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# End non-PEP attributes
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super(Cursor, self).__init__()
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def __repr__(self):
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is_closed = self._state == self._states.CURSOR_CLOSED
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return '<cursor object at 0x{0:x}; closed: {1:}>'.format(
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id(self), is_closed
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)
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# Iteration support.
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def __iter__(self):
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while True:
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one = self.fetchone()
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if one is None:
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return
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yield one
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# Context manager integrations.
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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self.close()
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@property
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def description(self):
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if self._state == self._states.NONE:
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return None
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columns = self._columns or []
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types = self._types or []
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return [
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Column(name, type_code, None, None, None, None, True)
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for name, type_code in zip(columns, types)
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]
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@property
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def rowcount(self):
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"""
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:return: the number of rows that the last .execute*() produced.
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"""
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return self._rowcount
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def close(self):
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"""
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Close the cursor now. The cursor will be unusable from this point
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forward; an :data:`~clickhouse_driver.dbapi.Error` (or subclass)
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exception will be raised if any operation is attempted with the
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cursor.
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"""
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self._client.disconnect()
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self._state = self._states.CURSOR_CLOSED
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try:
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# cursor can be already closed
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self._connection.cursors.remove(self)
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except ValueError:
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pass
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def execute(self, operation, parameters=None):
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"""
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Prepare and execute a database operation (query or command).
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:param operation: query or command to execute.
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:param parameters: sequence or mapping that will be bound to
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variables in the operation.
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:return: None
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"""
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self._check_cursor_closed()
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self._begin_query()
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try:
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execute, execute_kwargs = self._prepare()
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response = execute(
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operation, params=parameters, with_column_types=True,
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**execute_kwargs
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)
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except DriverError as orig:
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raise OperationalError(orig)
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self._process_response(response)
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self._end_query()
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def executemany(self, operation, seq_of_parameters):
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"""
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Prepare a database operation (query or command) and then execute it
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against all parameter sequences found in the sequence
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`seq_of_parameters`.
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:param operation: query or command to execute.
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:param seq_of_parameters: sequences or mappings for execution.
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:return: None
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"""
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self._check_cursor_closed()
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self._begin_query()
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try:
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execute, execute_kwargs = self._prepare()
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response = execute(
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operation, params=seq_of_parameters, **execute_kwargs
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)
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except DriverError as orig:
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raise OperationalError(orig)
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self._process_response(response, executemany=True)
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self._end_query()
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def fetchone(self):
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"""
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Fetch the next row of a query result set, returning a single sequence,
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or None when no more data is available.
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:return: the next row of a query result set or None.
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"""
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self._check_query_started()
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if self._stream_results:
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return next(self._rows, None)
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else:
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if not self._rows:
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return None
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return self._rows.pop(0)
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def fetchmany(self, size=None):
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"""
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Fetch the next set of rows of a query result, returning a sequence of
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sequences (e.g. a list of tuples). An empty sequence is returned when
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no more rows are available.
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:param size: amount of rows to return.
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:return: list of fetched rows or empty list.
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"""
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self._check_query_started()
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if size is None:
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size = self.arraysize
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if self._stream_results:
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if size == -1:
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return list(self._rows)
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else:
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return list(islice(self._rows, size))
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if size < 0:
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rv = self._rows
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self._rows = []
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else:
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rv = self._rows[:size]
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self._rows = self._rows[size:]
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return rv
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def fetchall(self):
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"""
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Fetch all (remaining) rows of a query result, returning them as a
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sequence of sequences (e.g. a list of tuples).
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:return: list of fetched rows.
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"""
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self._check_query_started()
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if self._stream_results:
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return list(self._rows)
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rv = self._rows
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self._rows = []
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return rv
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def setinputsizes(self, sizes):
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# Do nothing.
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pass
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def setoutputsize(self, size, column=None):
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# Do nothing.
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pass
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# Begin non-PEP methods
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@property
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def columns_with_types(self):
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"""
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:return: list of column names with corresponding types of the last
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.execute*(). E.g. [('x', 'UInt64')].
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"""
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return self._columns_with_types
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def set_stream_results(self, stream_results, max_row_buffer):
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"""
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Toggles results streaming from server. Driver will consume
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block-by-block of `max_row_buffer` size and yield row-by-row from each
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block.
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:param stream_results: enable or disable results streaming.
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:param max_row_buffer: specifies the maximum number of rows to buffer
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at a time.
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:return: None
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"""
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self._stream_results = stream_results
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self._max_row_buffer = max_row_buffer
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def set_settings(self, settings):
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"""
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Specifies settings for cursor.
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:param settings: dictionary of query settings
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:return: None
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"""
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self._settings = settings
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def set_types_check(self, types_check):
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"""
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Toggles type checking for sequence of INSERT parameters.
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Disabled by default.
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:param types_check: new types check value.
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:return: None
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"""
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self._types_check = types_check
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def set_external_table(self, name, structure, data):
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"""
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Adds external table to cursor context.
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If the same table is specified more than once the last one is used.
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:param name: name of external table
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:param structure: list of tuples (name, type) that defines table
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structure. Example [(x, 'Int32')].
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:param data: sequence of rows of tuples or dicts for transmission.
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:return: None
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"""
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self._external_tables[name] = (structure, data)
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def set_query_id(self, query_id):
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"""
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Specifies the query identifier for cursor.
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:param query_id: the query identifier.
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:return: None
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"""
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self._query_id = query_id
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# End non-PEP methods
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# Private methods.
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def _prepare(self):
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external_tables = [
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{'name': name, 'structure': structure, 'data': data}
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for name, (structure, data) in self._external_tables.items()
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] or None
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execute = self._client.execute
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if self._stream_results:
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execute = self._client.execute_iter
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self._settings = self._settings or {}
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self._settings['max_block_size'] = self._max_row_buffer
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execute_kwargs = {
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'settings': self._settings,
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'external_tables': external_tables,
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'types_check': self._types_check,
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'query_id': self._query_id
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}
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return execute, execute_kwargs
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def _process_response(self, response, executemany=False):
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if executemany:
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self._rowcount = response
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response = None
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if not response or isinstance(response, int):
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self._columns = self._types = self._rows = []
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if isinstance(response, int):
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self._rowcount = response
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return
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if self._stream_results:
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columns_with_types = next(response)
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rows = response
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else:
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rows, columns_with_types = response
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self._columns_with_types = columns_with_types
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# Only SELECT queries have columns_with_types.
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# DDL and INSERT INTO ... SELECT queries have empty columns header.
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# We need to obtain rows count only during non-streaming SELECTs.
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if columns_with_types:
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self._columns, self._types = zip(*columns_with_types)
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if not self._stream_results:
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self._rowcount = len(rows)
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else:
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self._columns = self._types = []
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self._rows = rows
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def _reset_state(self):
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"""
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Resets query state and get ready for another query.
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"""
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self._state = self._states.NONE
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self._columns = None
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self._types = None
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self._rows = None
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self._rowcount = -1
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self._stream_results = False
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self._max_row_buffer = 0
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self._settings = None
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self._query_id = None
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self._external_tables = {}
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self._types_check = False
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def _begin_query(self):
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self._state = self._states.RUNNING
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def _end_query(self):
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self._state = self._states.FINISHED
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def _check_cursor_closed(self):
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if self._state == self._states.CURSOR_CLOSED:
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raise InterfaceError('cursor already closed')
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def _check_query_started(self):
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if self._state == self._states.NONE:
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raise ProgrammingError('no results to fetch')
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