countEstimated

Counts all documents in the collection.

This function reads collection metadata instead of actually counting through all documents. This makes it much more performant (almost no CPU nor RAM usage), but the count may be slightly out of date.

In particular, it may become inaccurate when:

• there are orphaned documents in a shared cluster,

• an unclean shutdown happened.

Views do not possess the required metadata. When this function is called on a view (either a MongoDB view or a filter logical view), a regular count is executed instead.

External resources

• Official documentation

See also