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- mongo Shell Methods >
- Cursor Methods >
- cursor.snapshot()
cursor.snapshot()¶
- cursor.snapshot()¶
Append the snapshot() method to a cursor to toggle the “snapshot” mode. This ensures that the query will not return a document multiple times, even if intervening write operations result in a move of the document due to the growth in document size.
警告
- You must apply snapshot() to the cursor before retrieving any documents from the database.
- You can only use snapshot() with unsharded collections.
The snapshot() does not guarantee isolation from insertion or deletions.
The snapshot() traverses the index on the _id field. As such, snapshot() cannot be used with sort() or hint().
Queries with results of less than 1 megabyte are effectively implicitly snapshotted.