MongoDB: Does update overwrite same values?

Question

MongoDB

There is a code

db.test.test->insert ({_id: 1, key1: 'value1'})
db.test.test->update ({_id: 1}, {$set: {key1: 'value1'}})

Will the "new" value be written to disk or not? I didn't find it in the documentation.

Answer 1

Apparently, the record is not being made:

D:\MongoDB>mongo --verbose
MongoDB shell version: 2.6.3
...
> db.test.insert({_id:1, key1:"value1"})
WriteResult({ "nInserted" : 1 })
> db.test.update({_id:1}, {$set:{key1:"value1"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 0 })
> db.test.update({_id:1}, {$set:{key1:"value2"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Answer 2

Well, how could they not find it there in black and white at the very beginning it is written

Answer 3

Set the upsert parameter to true and if the element is found, it is overwritten, if not, it is inserted. Read more here