Mastering MongoDB 4.x - Second Edition

Update/remove

In document modifier operations, such as update and remove, we have a similar situation to the one we saw with find. If we have the shard key in the find section of the modifier, then mongos can direct the query to the relevant shard.

If we don't have the shard key in the find section, then it will again be a fanout operation.

The UpdateOne, replaceOne, and removeOne operations must have the shard key or the _id value.

The following table sums up the operations that we can use with sharding:

Type of operation	Query topology
Insert	Must have the shard key
Update	Can have the shard key
Query with shard key	Targeted operation
Query without shard key	Scatter-and-gather operation/fan out query