Casbah MongoDB, how to both add and remove values to an array in a single operation, to multiple documents?

Question

After searching, I was unable to figure out how to perform multiple updates to a single field.

I have a document with a "tags" array field. Every document will have random tags before I begin the update. In a single operation, I want to add some tags and remove some tags.

The following update operator returns an error "Invalid modifier specified: $and"

    updateOperators: { "$and" : [
      { "$addToSet" : { "tags" : { "$each" : [ "tag_1" , "tag_2"]}}},
      { "$pullAll" : { "tags" : [ "tag_2", "tag_3"]}}]}  

    collection.update(query, updateOperators, multi=true)  

How do I both add and remove values to an array in a single operation, to multiple documents?

Answer 1

You don't need the $and with the update query, but you cannot update two fields at the same time with an update - as you would see if you tried the following in the shell:

db.test.update({}, { "$addToSet" : { "tags" : { "$each" : [ "tag_1" , "tag_2"]}}, 
                     "$pullAll"  : { "tags" : [ "tag_2", "tag_3"] }}, true, false)

You would get a Cannot update 'tags' and 'tags' at the same time error message. So how to achieve this? Well with this schema you would need to do it in multiple operations, you could use the new bulk operation api as shown below (shell):

var bulk = db.coll.initializeOrderedBulkOp();
bulk.find({ "tags": 1 }).updateOne({ "$addToSet": { "$each" : [ "tag_1" , "tag_2"]}});
bulk.find({ "tags": 1 }).updateOne({ "$pullAll": { "tags": [ "tag_2", "tag_3"] } });
bulk.execute();

Or in Casbah with the dsl helpers:

val bulk = collection.initializeOrderedBulkOperation
bulk.find(MongoDBObject("tags" -> 1)).updateOne($addToSet("tags") $each("tag_1", tag_2"))
bulk.find(MongoDBObject("tags" -> 1)).updateOne($pullAll("tags" -> ("tags_2", "tags_3")))
bulk.execute()

Its not atomic and there is no guarantee that nothing else will try to modify, but it is as close as you will currently get.