在PHP中从集合中获取文档太长

Question

For example, I have inserted 10K documents in collection:

for ($i = 0; $i < 100; ++$i) {
    for ($j = 0; $j < 100; ++$j) {
        $collection->insert(array('i' => $i, 'j' => $j));
    }
}

I have created Indexes:

pkrs:PRIMARY> db.testTest.getIndexes()
[
        {
                "v" : 1,
                "key" : {
                        "_id" : 1
                },
                "ns" : "parts.testTest",
                "name" : "_id_"
        },
        {
                "v" : 1,
                "key" : {
                        "i" : 1,
                        "j" : 1
                },
                "ns" : "parts.testTest",
                "name" : "i_1_j_1"
        }
]

Then I want to fetch 600 documents with 'OR' condition:

for ($i = 5; $i < 12; ++$i) {
    for ($j = 0; $j < 100; ++$j) {
        $orArr[] = array('i'=>$i, 'j' => $j);
    }
}
$cursor = $collection->find(array('$or' => $orArr));
$cursor->batchSize(1000);
foreach ($cursor as $doc) {
   // code
}

And first document fetches about 1.5 second! :( How can I improve performance?