cursor
– Tools for iterating over MongoDB query results¶
Cursor class to iterate over Mongo query results.
- class pymongo.cursor.CursorType¶
- NON_TAILABLE¶
The standard cursor type.
- TAILABLE¶
The tailable cursor type.
Tailable cursors are only for use with capped collections. They are not closed when the last data is retrieved but are kept open and the cursor location marks the final document position. If more data is received iteration of the cursor will continue from the last document received.
- TAILABLE_AWAIT¶
A tailable cursor with the await option set.
Creates a tailable cursor that will wait for a few seconds after returning the full result set so that it can capture and return additional data added during the query.
- EXHAUST¶
An exhaust cursor.
MongoDB will stream batched results to the client without waiting for the client to request each batch, reducing latency.
- class pymongo.cursor.Cursor(collection, filter=None, projection=None, skip=0, limit=0, no_cursor_timeout=False, cursor_type=CursorType.NON_TAILABLE, sort=None, allow_partial_results=False, oplog_replay=False, batch_size=0, collation=None, hint=None, max_scan=None, max_time_ms=None, max=None, min=None, return_key=False, show_record_id=False, snapshot=False, comment=None, session=None, allow_disk_use=None)¶
Create a new cursor.
Should not be called directly by application developers - see
find()
instead.See also
The MongoDB documentation on cursors.
- c[index]
See
__getitem__()
and read the warning.
- __getitem__(index: int) pymongo.typings._DocumentType ¶
- __getitem__(index: slice) Cursor[_DocumentType]
Get a single document or a slice of documents from this cursor.
Warning
A
Cursor
is not a Pythonlist
. Each index access or slice requires that a new query be run using skip and limit. Do not iterate the cursor using index accesses. The following example is extremely inefficient and may return surprising results:cursor = db.collection.find() # Warning: This runs a new query for each document. # Don't do this! for idx in range(10): print(cursor[idx])
Raises
InvalidOperation
if this cursor has already been used.To get a single document use an integral index, e.g.:
>>> db.test.find()[50]
An
IndexError
will be raised if the index is negative or greater than the amount of documents in this cursor. Any limit previously 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 of20
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). RaisesIndexError
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
- add_option(mask: int) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Set arbitrary query flags using a bitmask.
To set the tailable flag: cursor.add_option(2)
- property address: Optional[Tuple[str, Any]]¶
The (host, port) of the server used, or None.
Changed in version 3.0: Renamed from “conn_id”.
- property alive: bool¶
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.
With regular cursors, simply use a for loop instead of
alive
:for doc in collection.find(): print(doc)
- allow_disk_use(allow_disk_use: bool) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Specifies whether MongoDB can use temporary disk files while processing a blocking sort operation.
Raises
TypeError
if allow_disk_use is not a boolean.Note
allow_disk_use requires server version >= 4.4
- Parameters
allow_disk_use: if True, MongoDB may use temporary disk files to store data exceeding the system memory limit while processing a blocking sort operation.
New in version 3.11.
- batch_size(batch_size: int) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Limits the number of documents returned in one batch. Each batch requires a round trip to the server. It can be adjusted to optimize performance and limit data transfer.
Note
batch_size can not override MongoDB’s internal limits on the amount of data it will return to the client in a single batch (i.e if you set batch size to 1,000,000,000, MongoDB will currently only return 4-16MB of results per batch).
Raises
TypeError
if batch_size is not an integer. RaisesValueError
if batch_size is less than0
. RaisesInvalidOperation
if thisCursor
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.
- clone() pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
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.
- collation(collation: Optional[Union[Mapping[str, Any], Collation]]) Cursor[_DocumentType] ¶
Adds a
Collation
to this query.Raises
TypeError
if collation is not an instance ofCollation
or adict
. RaisesInvalidOperation
if thisCursor
has already been used. Only the last collation applied to this cursor has any effect.- Parameters
collation: An instance of
Collation
.
- property collection: Collection[_DocumentType]¶
The
Collection
that thisCursor
is iterating.
- comment(comment: Any) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Adds a ‘comment’ to the cursor.
http://mongodb.com/docs/manual/reference/operator/comment/
- Parameters
comment: A string to attach to the query to help interpret and trace the operation in the server logs and in profile data.
New in version 2.7.
- distinct(key: str) List ¶
Get a list of distinct values for key among all documents in the result set of this query.
Raises
TypeError
if key is not an instance ofbasestring
(str
in python 3).The
distinct()
method obeys theread_preference
of theCollection
instance on whichfind()
was called.- Parameters
key: name of key for which we want to get the distinct values
- explain() pymongo.typings._DocumentType ¶
Returns an explain plan record for this cursor.
Note
This method uses the default verbosity mode of the explain command,
allPlansExecution
. To use a different verbosity usecommand()
to run the explain command directly.See also
The MongoDB documentation on explain.
- hint(index: Optional[Union[str, Sequence[Tuple[str, Union[int, str, Mapping[str, Any]]]]]]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
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. Raises
OperationFailure
if the provided hint requires an index that does not exist on this collection, and raisesInvalidOperation
if this cursor has already been used.index should be an index as passed to
create_index()
(e.g.[('field', ASCENDING)]
) or the name of the index. If index isNone
any existing hint for this query is cleared. The last hint applied to this cursor takes precedence over all others.- Parameters
index: index to hint on (as an index specifier)
- limit(limit: int) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Limits the number of results to be returned by this cursor.
Raises
TypeError
if limit is not an integer. RaisesInvalidOperation
if thisCursor
has already been used. The last limit applied to this cursor takes precedence. A limit of0
is equivalent to no limit.- Parameters
limit: the number of results to return
See also
The MongoDB documentation on limit.
- max(spec: Sequence[Tuple[str, Union[int, str, Mapping[str, Any]]]]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Adds
max
operator that specifies upper bound for specific index.When using
max
,hint()
should also be configured to ensure the query uses the expected index and starting in MongoDB 4.2hint()
will be required.- Parameters
spec: a list of field, limit pairs specifying the exclusive upper bound for all keys of a specific index in order.
Changed in version 3.8: Deprecated cursors that use
max
without ahint()
.New in version 2.7.
- max_await_time_ms(max_await_time_ms: Optional[int]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Specifies a time limit for a getMore operation on a
TAILABLE_AWAIT
cursor. For all other types of cursor max_await_time_ms is ignored.Raises
TypeError
if max_await_time_ms is not an integer orNone
. RaisesInvalidOperation
if thisCursor
has already been used.Note
max_await_time_ms requires server version >= 3.2
- Parameters
max_await_time_ms: the time limit after which the operation is aborted
New in version 3.2.
- max_scan(max_scan: Optional[int]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
DEPRECATED - Limit the number of documents to scan when performing the query.
Raises
InvalidOperation
if this cursor has already been used. Only the lastmax_scan()
applied to this cursor has any effect.- Parameters
max_scan: the maximum number of documents to scan
Changed in version 3.7: Deprecated
max_scan()
. Support for this option is deprecated in MongoDB 4.0. Usemax_time_ms()
instead to limit server side execution time.
- max_time_ms(max_time_ms: Optional[int]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Specifies a time limit for a query operation. If the specified time is exceeded, the operation will be aborted and
ExecutionTimeout
is raised. If max_time_ms isNone
no limit is applied.Raises
TypeError
if max_time_ms is not an integer orNone
. RaisesInvalidOperation
if thisCursor
has already been used.- Parameters
max_time_ms: the time limit after which the operation is aborted
- min(spec: Sequence[Tuple[str, Union[int, str, Mapping[str, Any]]]]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Adds
min
operator that specifies lower bound for specific index.When using
min
,hint()
should also be configured to ensure the query uses the expected index and starting in MongoDB 4.2hint()
will be required.- Parameters
spec: a list of field, limit pairs specifying the inclusive lower bound for all keys of a specific index in order.
Changed in version 3.8: Deprecated cursors that use
min
without ahint()
.New in version 2.7.
- next() pymongo.typings._DocumentType ¶
Advance the cursor.
- remove_option(mask: int) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Unset arbitrary query flags using a bitmask.
To unset the tailable flag: cursor.remove_option(2)
- rewind() pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Rewind this cursor to its 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.
- property session: Optional[ClientSession]¶
The cursor’s
ClientSession
, or None.New in version 3.6.
- skip(skip: int) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Skips the first skip results of this cursor.
Raises
TypeError
if skip is not an integer. RaisesValueError
if skip is less than0
. RaisesInvalidOperation
if thisCursor
has already been used. The last skip applied to this cursor takes precedence.- Parameters
skip: the number of results to skip
- sort(key_or_list: Union[str, Sequence[Tuple[str, Union[int, str, Mapping[str, Any]]]]], direction: Optional[Union[int, str]] = None) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Sorts this cursor’s results.
Pass a field name and a direction, either
ASCENDING
orDESCENDING
:for doc in collection.find().sort('field', pymongo.ASCENDING): print(doc)
To sort by multiple fields, pass a list of (key, direction) pairs:
for doc in collection.find().sort([ ('field1', pymongo.ASCENDING), ('field2', pymongo.DESCENDING)]): print(doc)
Text search results can be sorted by relevance:
cursor = db.test.find( {'$text': {'$search': 'some words'}}, {'score': {'$meta': 'textScore'}}) # Sort by 'score' field. cursor.sort([('score', {'$meta': 'textScore'})]) for doc in cursor: print(doc)
For more advanced text search functionality, see MongoDB’s Atlas Search.
Raises
InvalidOperation
if this cursor has already been used. Only the lastsort()
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
ASCENDING
is assumed
- where(code: Union[str, bson.code.Code]) pymongo.cursor.Cursor[pymongo.typings._DocumentType] ¶
Adds a $where clause to this query.
The code argument must be an instance of
basestring
(str
in python 3) orCode
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. For example:# Find all documents where field "a" is less than "b" plus "c". for doc in db.test.find().where('this.a < (this.b + this.c)'): print(doc)
Raises
TypeError
if code is not an instance ofbasestring
(str
in python 3). RaisesInvalidOperation
if thisCursor
has already been used. Only the last call towhere()
applied to aCursor
has any effect.- Parameters
code: JavaScript expression to use as a filter
- class pymongo.cursor.RawBatchCursor(collection, filter=None, projection=None, skip=0, limit=0, no_cursor_timeout=False, cursor_type=CursorType.NON_TAILABLE, sort=None, allow_partial_results=False, oplog_replay=False, batch_size=0, collation=None, hint=None, max_scan=None, max_time_ms=None, max=None, min=None, return_key=False, show_record_id=False, snapshot=False, comment=None, allow_disk_use=None)¶
Create a new cursor / iterator over raw batches of BSON data.
Should not be called directly by application developers - see
find_raw_batches()
instead.See also
The MongoDB documentation on cursors.