# Copyright 2009-2010 10gen, Inc. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. """Cursor class to iterate over Mongo query results.""" from bson.code import Code from bson.son import SON from pymongo import (helpers, message, ReadPreference) from pymongo.errors import (InvalidOperation, AutoReconnect) _QUERY_OPTIONS = { "tailable_cursor": 2, "slave_okay": 4, "oplog_replay": 8, "no_timeout": 16, "await_data": 32, "exhaust": 64, "partial": 128} # TODO might be cool to be able to do find().include("foo") or # find().exclude(["bar", "baz"]) or find().slice("a", 1, 2) as an # alternative to the fields specifier. class Cursor(object): """A cursor / iterator over Mongo query results. """ def __init__(self, collection, spec=None, fields=None, skip=0, limit=0, timeout=True, snapshot=False, tailable=False, sort=None, max_scan=None, as_class=None, slave_okay=False, await_data=False, partial=False, manipulate=True, read_preference=ReadPreference.PRIMARY, _must_use_master=False, _is_command=False, _uuid_subtype=None, **kwargs): """Create a new cursor. Should not be called directly by application developers - see :meth:`~pymongo.collection.Collection.find` instead. .. mongodoc:: cursors """ self.__id = None if spec is None: spec = {} if not isinstance(spec, dict): raise TypeError("spec must be an instance of dict") if not isinstance(skip, int): raise TypeError("skip must be an instance of int") if not isinstance(limit, int): raise TypeError("limit must be an instance of int") if not isinstance(timeout, bool): raise TypeError("timeout must be an instance of bool") if not isinstance(snapshot, bool): raise TypeError("snapshot must be an instance of bool") if not isinstance(tailable, bool): raise TypeError("tailable must be an instance of bool") if not isinstance(slave_okay, bool): raise TypeError("slave_okay must be an instance of bool") if not isinstance(await_data, bool): raise TypeError("await_data must be an instance of bool") if not isinstance(partial, bool): raise TypeError("partial must be an instance of bool") if fields is not None: if not fields: fields = {"_id": 1} if not isinstance(fields, dict): fields = helpers._fields_list_to_dict(fields) if as_class is None: as_class = collection.database.connection.document_class self.__collection = collection self.__spec = spec self.__fields = fields self.__skip = skip self.__limit = limit self.__batch_size = 0 # This is ugly. People want to be able to do cursor[5:5] and # get an empty result set (old behavior was an # exception). It's hard to do that right, though, because the # server uses limit(0) to mean 'no limit'. So we set __empty # in that case and check for it when iterating. We also unset # it anytime we change __limit. self.__empty = False self.__timeout = timeout self.__tailable = tailable self.__await_data = tailable and await_data self.__partial = partial self.__snapshot = snapshot self.__ordering = sort and helpers._index_document(sort) or None self.__max_scan = max_scan self.__explain = False self.__hint = None self.__as_class = as_class self.__slave_okay = slave_okay self.__manipulate = manipulate self.__read_preference = read_preference self.__tz_aware = collection.database.connection.tz_aware self.__must_use_master = _must_use_master self.__is_command = _is_command self.__uuid_subtype = _uuid_subtype or collection.uuid_subtype self.__query_flags = 0 self.__data = [] self.__connection_id = None self.__retrieved = 0 self.__killed = False # this is for passing network_timeout through if it's specified # need to use kwargs as None is a legit value for network_timeout self.__kwargs = kwargs @property def collection(self): """The :class:`~pymongo.collection.Collection` that this :class:`Cursor` is iterating. .. versionadded:: 1.1 """ return self.__collection def __del__(self): if self.__id and not self.__killed: self.__die() def rewind(self): """Rewind this cursor to it's unevaluated state. Reset this cursor if it has been partially or completely evaluated. Any options that are present on the cursor will remain in effect. Future iterating performed on this cursor will cause new queries to be sent to the server, even if the resultant data has already been retrieved by this cursor. """ self.__data = [] self.__id = None self.__connection_id = None self.__retrieved = 0 self.__killed = False return self def clone(self): """Get a clone of this cursor. Returns a new Cursor instance with options matching those that have been set on the current instance. The clone will be completely unevaluated, even if the current instance has been partially or completely evaluated. """ copy = Cursor(self.__collection, self.__spec, self.__fields, self.__skip, self.__limit, self.__timeout, self.__snapshot, self.__tailable) copy.__ordering = self.__ordering copy.__explain = self.__explain copy.__hint = self.__hint copy.__batch_size = self.__batch_size copy.__max_scan = self.__max_scan copy.__as_class = self.__as_class copy.__slave_okay = self.__slave_okay copy.__await_data = self.__await_data copy.__partial = self.__partial copy.__manipulate = self.__manipulate copy.__read_preference = self.__read_preference copy.__must_use_master = self.__must_use_master copy.__is_command = self.__is_command copy.__uuid_subtype = self.__uuid_subtype copy.__query_flags = self.__query_flags copy.__kwargs = self.__kwargs return copy def __die(self): """Closes this cursor. """ if self.__id and not self.__killed: connection = self.__collection.database.connection if self.__connection_id is not None: connection.close_cursor(self.__id, self.__connection_id) else: connection.close_cursor(self.__id) self.__killed = True def close(self): """Explicitly close this cursor. Required for PyPy, Jython and other Python implementations that don't use reference counting garbage collection. """ self.__die() def __query_spec(self): """Get the spec to use for a query. """ spec = self.__spec if not self.__is_command and "$query" not in self.__spec: spec = SON({"$query": self.__spec}) if self.__ordering: spec["$orderby"] = self.__ordering if self.__explain: spec["$explain"] = True if self.__hint: spec["$hint"] = self.__hint if self.__snapshot: spec["$snapshot"] = True if self.__max_scan: spec["$maxScan"] = self.__max_scan return spec def __query_options(self): """Get the query options string to use for this query. """ options = self.__query_flags if self.__tailable: options |= _QUERY_OPTIONS["tailable_cursor"] if self.__slave_okay or self.__read_preference: options |= _QUERY_OPTIONS["slave_okay"] if not self.__timeout: options |= _QUERY_OPTIONS["no_timeout"] if self.__await_data: options |= _QUERY_OPTIONS["await_data"] if self.__partial: options |= _QUERY_OPTIONS["partial"] return options def __check_okay_to_chain(self): """Check if it is okay to chain more options onto this cursor. """ if self.__retrieved or self.__id is not None: raise InvalidOperation("cannot set options after executing query") def add_option(self, mask): """Set arbitary query flags using a bitmask. To set the tailable flag: cursor.add_option(2) """ if not isinstance(mask, int): raise TypeError("mask must be an int") self.__check_okay_to_chain() self.__query_flags |= mask return self def remove_option(self, mask): """Unset arbitrary query flags using a bitmask. To unset the tailable flag: cursor.remove_option(2) """ if not isinstance(mask, int): raise TypeError("mask must be an int") self.__check_okay_to_chain() self.__query_flags &= ~mask return self def limit(self, limit): """Limits the number of results to be returned by this cursor. Raises TypeError if limit is not an instance of int. Raises InvalidOperation if this cursor has already been used. The last `limit` applied to this cursor takes precedence. A limit of ``0`` is equivalent to no limit. :Parameters: - `limit`: the number of results to return .. mongodoc:: limit """ if not isinstance(limit, int): raise TypeError("limit must be an int") self.__check_okay_to_chain() self.__empty = False self.__limit = limit return self def batch_size(self, batch_size): """Set the size for batches of results returned by this cursor. Raises :class:`TypeError` if `batch_size` is not an instance of :class:`int`. Raises :class:`ValueError` if `batch_size` is less than ``0``. Raises :class:`~pymongo.errors.InvalidOperation` if this :class:`Cursor` has already been used. The last `batch_size` applied to this cursor takes precedence. :Parameters: - `batch_size`: The size of each batch of results requested. .. versionadded:: 1.9 """ if not isinstance(batch_size, int): raise TypeError("batch_size must be an int") if batch_size < 0: raise ValueError("batch_size must be >= 0") self.__check_okay_to_chain() self.__batch_size = batch_size == 1 and 2 or batch_size return self def skip(self, skip): """Skips the first `skip` results of this cursor. Raises TypeError if skip is not an instance of int. Raises InvalidOperation if this cursor has already been used. The last `skip` applied to this cursor takes precedence. :Parameters: - `skip`: the number of results to skip """ if not isinstance(skip, (int, long)): raise TypeError("skip must be an int") self.__check_okay_to_chain() self.__skip = skip return self def __getitem__(self, index): """Get a single document or a slice of documents from this cursor. Raises :class:`~pymongo.errors.InvalidOperation` if this cursor has already been used. To get a single document use an integral index, e.g.:: >>> db.test.find()[50] An :class:`IndexError` will be raised if the index is negative or greater than the amount of documents in this cursor. Any limit applied to this cursor will be ignored. To get a slice of documents use a slice index, e.g.:: >>> db.test.find()[20:25] This will return this cursor with a limit of ``5`` and skip of ``20`` applied. Using a slice index will override any prior limits or skips applied to this cursor (including those applied through previous calls to this method). Raises :class:`IndexError` when the slice has a step, a negative start value, or a stop value less than or equal to the start value. :Parameters: - `index`: An integer or slice index to be applied to this cursor """ self.__check_okay_to_chain() self.__empty = False if isinstance(index, slice): if index.step is not None: raise IndexError("Cursor instances do not support slice steps") skip = 0 if index.start is not None: if index.start < 0: raise IndexError("Cursor instances do not support" "negative indices") skip = index.start if index.stop is not None: limit = index.stop - skip if limit < 0: raise IndexError("stop index must be greater than start" "index for slice %r" % index) if limit == 0: self.__empty = True else: limit = 0 self.__skip = skip self.__limit = limit return self if isinstance(index, (int, long)): if index < 0: raise IndexError("Cursor instances do not support negative" "indices") clone = self.clone() clone.skip(index + self.__skip) clone.limit(-1) # use a hard limit for doc in clone: return doc raise IndexError("no such item for Cursor instance") raise TypeError("index %r cannot be applied to Cursor " "instances" % index) def max_scan(self, max_scan): """Limit the number of documents to scan when performing the query. Raises :class:`~pymongo.errors.InvalidOperation` if this cursor has already been used. Only the last :meth:`max_scan` applied to this cursor has any effect. :Parameters: - `max_scan`: the maximum number of documents to scan .. note:: Requires server version **>= 1.5.1** .. versionadded:: 1.7 """ self.__check_okay_to_chain() self.__max_scan = max_scan return self def sort(self, key_or_list, direction=None): """Sorts this cursor's results. Takes either a single key and a direction, or a list of (key, direction) pairs. The key(s) must be an instance of ``(str, unicode)``, and the direction(s) must be one of (:data:`~pymongo.ASCENDING`, :data:`~pymongo.DESCENDING`). Raises :class:`~pymongo.errors.InvalidOperation` if this cursor has already been used. Only the last :meth:`sort` applied to this cursor has any effect. :Parameters: - `key_or_list`: a single key or a list of (key, direction) pairs specifying the keys to sort on - `direction` (optional): only used if `key_or_list` is a single key, if not given :data:`~pymongo.ASCENDING` is assumed """ self.__check_okay_to_chain() keys = helpers._index_list(key_or_list, direction) self.__ordering = helpers._index_document(keys) return self def count(self, with_limit_and_skip=False): """Get the size of the results set for this query. Returns the number of documents in the results set for this query. Does not take :meth:`limit` and :meth:`skip` into account by default - set `with_limit_and_skip` to ``True`` if that is the desired behavior. Raises :class:`~pymongo.errors.OperationFailure` on a database error. With :class:`~pymongo.replica_set_connection.ReplicaSetConnection` or :class:`~pymongo.master_slave_connection.MasterSlaveConnection`, if `read_preference` is not :attr:`pymongo.ReadPreference.PRIMARY` or (deprecated) `slave_okay` is `True` the count command will be sent to a secondary or slave. :Parameters: - `with_limit_and_skip` (optional): take any :meth:`limit` or :meth:`skip` that has been applied to this cursor into account when getting the count .. note:: The `with_limit_and_skip` parameter requires server version **>= 1.1.4-** .. versionadded:: 1.1.1 The `with_limit_and_skip` parameter. :meth:`~pymongo.cursor.Cursor.__len__` was deprecated in favor of calling :meth:`count` with `with_limit_and_skip` set to ``True``. """ command = {"query": self.__spec, "fields": self.__fields} command['read_preference'] = self.__read_preference command['slave_okay'] = self.__slave_okay use_master = not self.__slave_okay and not self.__read_preference command['_use_master'] = use_master if with_limit_and_skip: if self.__limit: command["limit"] = self.__limit if self.__skip: command["skip"] = self.__skip database = self.__collection.database r = database.command("count", self.__collection.name, allowable_errors=["ns missing"], uuid_subtype = self.__uuid_subtype, **command) if r.get("errmsg", "") == "ns missing": return 0 return int(r["n"]) def distinct(self, key): """Get a list of distinct values for `key` among all documents in the result set of this query. Raises :class:`TypeError` if `key` is not an instance of :class:`basestring`. With :class:`~pymongo.replica_set_connection.ReplicaSetConnection` or :class:`~pymongo.master_slave_connection.MasterSlaveConnection`, if `read_preference` is not :attr:`pymongo.ReadPreference.PRIMARY` or (deprecated) `slave_okay` is `True` the distinct command will be sent to a secondary or slave. :Parameters: - `key`: name of key for which we want to get the distinct values .. note:: Requires server version **>= 1.1.3+** .. seealso:: :meth:`pymongo.collection.Collection.distinct` .. versionadded:: 1.2 """ if not isinstance(key, basestring): raise TypeError("key must be an instance of basestring") options = {"key": key} if self.__spec: options["query"] = self.__spec options['read_preference'] = self.__read_preference options['slave_okay'] = self.__slave_okay use_master = not self.__slave_okay and not self.__read_preference options['_use_master'] = use_master database = self.__collection.database return database.command("distinct", self.__collection.name, uuid_subtype = self.__uuid_subtype, **options)["values"] def explain(self): """Returns an explain plan record for this cursor. .. mongodoc:: explain """ c = self.clone() c.__explain = True # always use a hard limit for explains if c.__limit: c.__limit = -abs(c.__limit) return c.next() def hint(self, index): """Adds a 'hint', telling Mongo the proper index to use for the query. Judicious use of hints can greatly improve query performance. When doing a query on multiple fields (at least one of which is indexed) pass the indexed field as a hint to the query. Hinting will not do anything if the corresponding index does not exist. Raises :class:`~pymongo.errors.InvalidOperation` if this cursor has already been used. `index` should be an index as passed to :meth:`~pymongo.collection.Collection.create_index` (e.g. ``[('field', ASCENDING)]``). If `index` is ``None`` any existing hints for this query are cleared. The last hint applied to this cursor takes precedence over all others. :Parameters: - `index`: index to hint on (as an index specifier) """ self.__check_okay_to_chain() if index is None: self.__hint = None return self self.__hint = helpers._index_document(index) return self def where(self, code): """Adds a $where clause to this query. The `code` argument must be an instance of :class:`basestring` or :class:`~bson.code.Code` containing a JavaScript expression. This expression will be evaluated for each document scanned. Only those documents for which the expression evaluates to *true* will be returned as results. The keyword *this* refers to the object currently being scanned. Raises :class:`TypeError` if `code` is not an instance of :class:`basestring`. Raises :class:`~pymongo.errors.InvalidOperation` if this :class:`Cursor` has already been used. Only the last call to :meth:`where` applied to a :class:`Cursor` has any effect. :Parameters: - `code`: JavaScript expression to use as a filter """ self.__check_okay_to_chain() if not isinstance(code, Code): code = Code(code) self.__spec["$where"] = code return self def __send_message(self, message): """Send a query or getmore message and handles the response. """ db = self.__collection.database kwargs = {"_must_use_master": self.__must_use_master} kwargs["read_preference"] = self.__read_preference if self.__connection_id is not None: kwargs["_connection_to_use"] = self.__connection_id kwargs.update(self.__kwargs) response = db.connection._send_message_with_response(message, **kwargs) if isinstance(response, tuple): (connection_id, response) = response else: connection_id = None self.__connection_id = connection_id try: response = helpers._unpack_response(response, self.__id, self.__as_class, self.__tz_aware) except AutoReconnect: db.connection.disconnect() raise self.__id = response["cursor_id"] # starting from doesn't get set on getmore's for tailable cursors if not self.__tailable: assert response["starting_from"] == self.__retrieved self.__retrieved += response["number_returned"] self.__data = response["data"] if self.__limit and self.__id and self.__limit <= self.__retrieved: self.__die() def _refresh(self): """Refreshes the cursor with more data from Mongo. Returns the length of self.__data after refresh. Will exit early if self.__data is already non-empty. Raises OperationFailure when the cursor cannot be refreshed due to an error on the query. """ if len(self.__data) or self.__killed: return len(self.__data) if self.__id is None: # Query ntoreturn = self.__batch_size if self.__limit: if self.__batch_size: ntoreturn = min(self.__limit, self.__batch_size) else: ntoreturn = self.__limit self.__send_message( message.query(self.__query_options(), self.__collection.full_name, self.__skip, ntoreturn, self.__query_spec(), self.__fields, self.__uuid_subtype)) if not self.__id: self.__killed = True elif self.__id: # Get More if self.__limit: limit = self.__limit - self.__retrieved if self.__batch_size: limit = min(limit, self.__batch_size) else: limit = self.__batch_size self.__send_message( message.get_more(self.__collection.full_name, limit, self.__id)) return len(self.__data) @property def alive(self): """Does this cursor have the potential to return more data? This is mostly useful with `tailable cursors `_ since they will stop iterating even though they *may* return more results in the future. .. versionadded:: 1.5 """ return bool(len(self.__data) or (not self.__killed)) def __iter__(self): return self def next(self): if self.__empty: raise StopIteration db = self.__collection.database if len(self.__data) or self._refresh(): if self.__manipulate: return db._fix_outgoing(self.__data.pop(0), self.__collection) else: return self.__data.pop(0) else: raise StopIteration def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): self.__die()