Normally you would use the following to remove a field from a collection. However the code below does not work for empty ("") fields. How would you go about deleting an empty field in MongoDB?
db.collection.update({}, {$unset: {"": ""}}, {multi:true})
I get the following error message when I try this:
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"nModified" : 0,
"writeError" : {
"code" : 56,
"errmsg" : "An empty update path is not valid."
}
})
It looks like empty string keys must only be partially supported by MongoDB.
This isn't as efficient as a multi-update, but it does work to remove those fields in the shell:
db.collection.find().forEach(function(doc) {
delete doc[''];
db.collection.save(doc);
});
To do this using the update or updateMany method, you must specify the parameter you want to update, such as name:
db.collection.updateMany({name: ""}, { $unset : { name : 1 }})
If you need to delete rows with the field, that is empty, you can use:
db.collection.deleteMany({ 'myField': null})
Updated for mongodb version 4.2+ (db.collection.save is no longer supported)
Empty field keys aren't fully supported by mongodb, and look like they are going to be depreciated.
To get rid of empty field keys
db.collection.find({"":{$exists:true}).forEach(
(doc)=>{
delete doc[""];
db.collection.replaceOne(doc,doc,{upsert:true})
})
