教义ODM（MongoDB）MapReduce +跳过

Question

I'm working on with a set where I need to use batch-querying due to Doctrine's - and Mongo's - reduce output limitations. However, I'm stupefied about how to do so.

Doctrine ODM's MapReduce doesn't allow the Skip option. However, I've found and read about injecting a variable into Scope (let's say n ), where it can act as a global counter for the MapReduce , and with an if() check it can effectively skip emits where the counter is less than n .

However, those explanations were for MongoDB's JS implementations (mongoose etc.), whereas I'm working with Doctrine ODM, so I've no idea how to go about this.

Thanks in advance.

Answer 1

After a bit of digging through the QueryBuilder class, I've found mapReduceOptions(array) so added the following to my query after the map :

->mapReduceOptions(array('scope'=>array('skip'=>$BatchSkip,'counter'=>0)))`

ie

->map($map)
->mapReduceOptions(array('scope'=>array('skip'=>$BatchSkip,'counter'=>0)))
->reduce($reduce)
->getQuery()->execute()

I then wrapped everything in my map function with if (counter >= skip && counter < (skip+100))

$map = "function(){
  if (counter >= skip && counter < (skip+100))
  { 
    .
    .
    .
    emit( key, value ); 
  }";

and I increment $BatchSkip in my PHP batch loop.

$BatchSkip+=100;

That does the trick. Reference: MongoDB mapReduce options: https://docs.mongodb.com/manual/reference/command/mapReduce/#mapreduce