Should I use the “allowDiskUse” option in a product environment?

Question

Should I use the allowDiskUse option when returned doc exceed 16MB limit in aggregation?

Or should I alter db structure or codes logic to avoid the limit? What\'s

Answer 1

allowDiskUse is unrelated to the 16MB result size limit. That setting controls whether pipeline steps such as $sort or $group can use some temporary disk space if they need more than 100MB of memory. In theory, for an arbitrary pipeline this could be a very large amount of diskspace. Personally it's never been a problem, but that will be down to your data.

If your result is going to be more than 16MB then you need to use the $out pipeline stage to output the data to a collection or use a pipeline API that returns a cursor to results instead of returning all the data inline (for some drivers this is a separate method, for others it is a flag passed to the same method).