[question] Replacement fore MongoCode ? about mongo-php-library

[jacqueswaller]

I think the MongoDB\BSON\Javascript class is the equivalent though I haven't used it yet.

[flashjay]

usage:

MongoDB\Database::command(['eval' =>"function() { return {$func}; }", 'args' => $args, 'nolock' => true])

[jmikola]

As @jacqueswaller suggested, MongoDB\BSON\Javascript class is the new driver's equivalent for the legacy MongoCode class. @flashjay's example appears to work because the server happens to accept a string for the eval command; however, I'm not sure if other JavaScript commands (e.g. mapReduce) do the same. Either way, I would suggest using the Javascript class in your application so not to depend on any undocumented server behavior.

As for the code example in the original question, there is really no need for Javascript evaluation in that scenario. You will generally be much better off iterating on the blog posts in PHP and issuing multiple updates (via BulkWrite). Using the aggregation framework, you can do this in a two-step operation (i.e. two round trips to the server):

1. Construct an aggregation pipeline to $group on the comments collection, using the blog ID as the bucket identifier ($id) and projecting a running count into a separate field (i.e. {$sum: 1}).
2. Create a BulkWrite object and append updates for each aggregate result, setting the blog post's n field accordingly.

The above situation would only handle blog posts with at least one comment, so you may want to lead with a mass update on blog posts to set n to zero for all posts. Alternatively, you can lead with a separate query for all blog post IDs to collect them and diff against the aggregation results. For each post not in the aggregation results, you could then explicitly set it to zero.

[Alsatian67]

@jmikola I just tried your method with aggregator, and it works fine.
Thank you very much for the explaination.