MongoDB the total number of records to query for data that does not duplicate

Lead: db.keyword.distinct ("keyword"). length

As follows:

Db.keyword.distinct ("keyword"). length

View the total number of records in the keyword table that do not duplicate keyword fields

This method is not seen in the official document, try to find the original can also be used like that

Db.keyword.find (). Length () ==db.keyword.find (). Count ()

Of course, the length here must be parenthesis.

However, this method is only suitable for a small number of data, test 200,000 can be, more than 1 million of the time is not, the report data is too large, we can see according to the actual situation he probably supported how much data.

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