PROJECTION_DEFAULT
Means that MongoDB is using the standard/default way of selecting which fields to return in the query result
Detailed Description​
PROJECTION_DEFAULT in MongoDB explain plans simply means that MongoDB is using the standard/default way of selecting which fields to return in the query result. In other words, unless you requested a special or advanced projection (like returning just matched elements in an array), MongoDB represents the default projection mode as PROJECTION_DEFAULT.
In simple terms:
If you only include or exclude fields in your query (e.g., {title: 1, year: 1}), MongoDB uses PROJECTION_DEFAULT. This is the regular way MongoDB handles which fields to return in your documents.
You do not need to do anything special when you see PROJECTION_DEFAULT—it's how MongoDB normally projects results unless you use advanced operators.
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