How to rename all the key in mongodb? - mongodb

Question

i have a documents like this :
{
"_id" : ObjectId("5705fe62d0d50b2316617508"),
"date" : ISODate("2016-04-07T11:12:43.917Z"),
}
{
"_id" : ObjectId("5705fe62d0d50b2316617508"),
"date" : ISODate("2016-04-07T11:12:43.917Z"),
"XString" : "bb"
}
{
"_id" : ObjectId("5705fe62d0d50b2316617508"),
"date" : ISODate("2016-04-07T11:12:43.917Z"),
"XString" : "ba"
}
{
"_id" : ObjectId("5705fe62d0d50b2316617508"),
"date" : ISODate("2016-04-07T11:12:43.917Z"),
"XString" : "dd"
}
how i can update key "XString" to "Name" and if the XString is not there it should add "Name"
tried by using $rename as:
db.articles.update({}, {$set:{$rename: {'XString':'Name'}}},{upsert:true});
but it gives error as:
The dollar ($) prefixed field '$rename' in '$rename' is not valid for storage.
Tried other way:
db.articles.update({}, {$rename: {'XString': 'Name'}}, false, true);
but its not adding the key is it does not exists

Answer 1

Wrong option. You want "multi" and not "upsert":
db.articles.update(
{ "XString": { "$exists": true } },
{ "$rename": { 'XString': 'Name' } },
{ "multi": true }
);
The $exists test makes sure you are only selecting documents where the key you are renaming is actually there.
Also $rename is a "update modifier" which means it is a "top level" argument of the "update" document.
The "multi" means to affect all matched documents, rather than just the "first".
If you want a "blank" value where the key does not actually exist then you do the opposite, and preferably after the $rename operation:
db.articles.update(
{ "Name": { "$exists": false } },
{ "$set": { 'Name': '' } },
{ "multi": true }
);

Answer 2

If your MongoDB server version is 3.2 you can use the updateMany() method. Of course you need to use $exists and $rename as already mentioned in this answer. Also the updateMany() method doesn't take the "multi" option.
Last but not least major drivers deprecate the update() method since version 3.0
The following query rename "XString" to "Name" where "XString" exists.
db.articles.updateMany(
{ "XString": { "$exists": true } },
{ "$rename": { "XString": "Name" } }
)
To set default value where the "XString" doesn't exist, use the $set update operator.
db.articles.updateMany(
{ "Name": { "$exists": false } },
{ "$set": { "Name": "" } }
)