Multiply field by value in Mongodb

Question

I\'ve been looking for a way to create an update statement that will take an existing numeric field and modify it using an expression. For example, if I have a field called

Answer 1

Well, this is possible with an atomic operation as $set.

You have several options :

• use the eval() solution proposed by pingw33n
• retrieve the document you want to modify to get the current value and modify it with a set
• if you have a high operation rate, you might want to be sure the focument has not changed during you fetch its value (using the previous solution) so you might want to use a findAndModify (see this page to get inspired on how to do it) operation.

It really depends on your context : with a very low pressure on the db, I'd go for the solution of pingw33n. With a very high operation rate, I'd use the third solution.