Why can't I run explain on MongoDB update?

Question

I'm trying to explain a mongoDB update; but nothing is happening? Does Mongo not support this?

> db.movies.update({"actors.name": "Christian Bale"}, {$set: {"actors.$.name": "Christina Bale"}}, {$explain: 1});
>

I've tried other variations using .explain() and ._addSpecial("$explain", 1"). Both of these produce the following error:

Thu Aug 1 11:26:46.368 JavaScript execution failed: TypeError: Cannot call method 'explain' of undefined

Answer 1

I believe the following will allow you to call explain on your query.

    db.movies.explain().update({your_query})

Hope this helps, if you need more info let me know.

Answer 2

Why do you want to call explain on update? AFAIK, explain will show you how your query will fetch the rows, so you could simply do:

db.movies.find(
    {$query:  {"actors.name": "Christian Bale"}},
    {$explain: 1}
);