(PECL mongo >=0.9.4)
MongoCursor::snapshot — Use snapshot mode for the query
Use snapshot mode for the query. Snapshot mode ensures that a document will not be returned more than once because an intervening write operation results in a move of the document. Documents inserted or deleted during the lifetime of the cursor may or may not be returned, irrespective of snapshot mode.
Queries with short responses (less than 1MB) are always effectively snapshotted.
Snapshot mode may not be used with sorting, explicit hints, or queries on sharded collections.
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Returns this cursor.
Throws MongoCursorException if this cursor has started iterating.
MongoDB core docs on » $snapshot operator.