Ruby map/collect is slow on a large Mongoid collection -

I have a casual collection on which I run where query.

Now, I want to create an array with the value of a specific field from all the documents present in the archive.

For example if I have a monogid model

  square fu field: color, type: string end  

let me do something like this -

  red_ducks = Foo.where (color: 'red') red_duck_ids = red_ducks.map (& amp;: _ id)  

Unfortunately , When the result of the query is large it takes a lot of time. For example, in my case, 10,000 documents take 6 seconds.

Is there any way to speed up this speed?

Can not you just call different calls to your circle with _id as a property?

red_duck_ids = Foo.where (color: 'red'). Specific (: _ID)

will return a list of all the _id that meet your conditions and more information on you.

You can also see and you can use it if you are using version 3.1 or newer.