$push and $set in same MongoDB update

问题:

I'm trying to use MongoDB's Java driver to make two updates ($set and $push) to a record in the same operation. I'm using code similar to the following:

    BasicDBObject pushUpdate = new BasicDBObject().append("$push", new BasicDBObject().append("values", dboVital));
    BasicDBObject setUpdate = new BasicDBObject().append("$set", new BasicDBObject().append("endTime", time));
    BasicDBList combinedUpdate = new BasicDBList();
    combinedUpdate.add( pushUpdate);        
    combinedUpdate.add( setUpdate);


    collection.update( new BasicDBObject().append("_id", pageId), combinedUpdate, true, false);

When I combine the $set and $push into the same update via a BasicDBList, I get an IllegalArgumentException: "fields stored in the db can't start with '$' (Bad Key: '$push')".

If I make two separate updates, both pushUpdate and setUpdate produce valid results.

Thanks!

回答1:

I don't know Java driver, but do you have to create a list there? What happens if you try this code?

BasicDBObject update = new BasicDBObject().append("$push", new BasicDBObject().append("values", dboVital));
update = update.append("$set", new BasicDBObject().append("endTime", time));

collection.update( new BasicDBObject().append("_id", pageId), update, true, false);

This should produce the equivalent of

db.collection.update({_id: pageId}, {$push: {values: dboVital}, $set: {endTime: time}});

Whereas your code produces (I suspect) this:

db.collection.update({_id: pageId}, [{$push: {values: dboVital}}, {$set: {endTime: time}}]);

回答2:

My mongodb version is 3.4.20 and while using

db.collection.update({_id: pageId}, [{$push: {values: dboVital}}, {$set: {endTime: time}}]);

I received error

[thread1] Error: field names cannot start with $ [$push] :

To solve that error we can use:

db.collection.update({_id: pageId}, {$push: {values: dboVital}, $set: {endTime: time}});