A question about updateMany():
According to the documentation, the response includes
Is it possible that the two numbers are different, i.e. that it was not possible to update a document for some reason?
And how do I find out which one it is?
I can’t find anything about this in the documentation …
Yes. If modifiedCount is smaller than matchedCount, it means that some matched documents were not modified because they already contained the correct updated value. For example,
{ _id : 0 , a : 0 , b : 2 }
{ _id : 1 , a : 0 , b : 3 }
updateMany( { a : 0 } , { $set : { b : 2 } } )
Both documents _id:0 and _id:1 match the query a:0 so matchedCount=2 but since _id:0 already has b:2 it is not modified. Then modifiedCount=1.
I have not seen a condition where modifiedCount is > matchedCount.
I do not know.
Hi @steevej,
thanks for your response.
That’s fine since that means when the updateMany() is finished all matched documents match the expected state regarding the update.
In this case the difference between matchedCount and modifiedCount is fine.
And how do I find out which one it is?
In fact that is only relevant for me if this would mean that one or more documents could not be updated for some other reason than you mentioned. Meaning that updating a document failed and it does not match the expected update state.
| Topic | Replies | Views | Activity |
|---|---|---|---|
| Serveless instance questions | 1 | 523 | May 2024 |
| All user to view MongoDB Atlas user last login timestamp | 0 | 331 | Jun 2024 |
| OPLog Configuration missing on atlas | 1 | 253 | Jun 2024 |
| Network configuration MongoDB Replicaset | 2 | 55 | Oct 2024 |
| Low perf on regex search even on M50 instance | 1 | 33 | Nov 2024 |