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Refactor count to count_documents and estimated_document_count
#62
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PyMongo `~=4.0` removes `Cursor.count` and `Collection.count` and provides two new count methods: `Collection.count_documents` and `Collection.estimated_document_count`. Both `Cursor.count` and `Collection.count` in PyMongo `~=3.0` use `count` MongoDB command, which provide potentially inaccurate results when executd without a query predicate, in a transaction, or on a sharded cluster. `Collection.count_documents` issues an aggregate query, which is accurate in all cases, but relatively expensive. `Collection.estimated_document_count` in PyMongo `>=4.0,<4.2` uses a $collStats aggregation to estimate the document count for the collection. In PyMongo `>4.2` it relies on the `count` MongoDB command. When possible, we now try using the estimated document count for count operations, but if a limit or skip is defined, or a hint is provided, we'll use the more accurate count. This mirrors the behavior of the upstream mongoengine implementation.
wojcikstefan
approved these changes
Jan 23, 2025
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PyMongo
~=4.0removesCursor.countandCollection.countand provides two new count methods:Collection.count_documentsandCollection.estimated_document_count. 1When possible, we now try using the estimated document count for count operations, but if a limit or skip is defined, or a hint is provided, we'll use the more accurate count. This mirrors the behavior of the upstream mongoengine implementation.
Collection.count_documentsissues an aggregate query, which is accurate in all cases, but relatively expensive.Collection.estimated_document_countin PyMongo>=4.0,<4.2uses a $collStats aggregation to estimate the document count for the collection. In PyMongo>4.2it relies on thecountMongoDB command.Footnotes
https://pymongo.readthedocs.io/en/stable/migrate-to-pymongo4.html#collection-count-and-cursor-count-is-removed ↩