根据当前值更新MongoDB中的值 [英] Update a value in MongoDB based on its current value

问题描述

我想做这样的事情，但是this关键字似乎没有在更新语句中设置.

I want to do something like this, but the this keyword doesn't seem to be set inside the update statement.

db.items.update({foo:…}, {$set: {bar: this.foo}}, false, true)

我必须使用eval来完成此操作吗?

Do I have to use eval to accomplish this?

推荐答案

是的，您不能在修饰符中引用其他字段.您必须使用db.eval.

Yes, you can't refer to other fields in the modifier. You'll have to use db.eval.

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