What is the fastest way to see when the last update to MongoDB was made

问题

I'm writing a long-polling script to check for new documents in my mongo collection and the only way I know of checking to see whether or not changes have been made in the past iteration of my loop is to do a query getting the last document's ID and parsing out the timestamp in that ID and seeing if it's greater than the timestamp left since I last made a request.

Is there some kind of approach that doesn't involve making a query every time or something that makes that query the fastest?

I was thinking a query like this:

db.chat.find().sort({_id:-1}).limit(1);

But it would be using the PHP driver.

回答1:

The fastest way will be creating indexes on timestamp field.

Creating index:

db.posts.ensureIndex( { timestamp : 1 } )

Optimizes this query:

db.posts.find().sort( { timestamp : -1 } )

findOne give you only one the last timestamp.

nice to help you.

回答2:

@Zagorulkin Your suggestion is surely going to help in the required scenario. However i don't think so sort() works with findOne().

来源：https://stackoverflow.com/questions/14332101/what-is-the-fastest-way-to-see-when-the-last-update-to-mongodb-was-made