I run this command:
db.ads_view.aggregate({$group: {_id : "$campaign", "action" : {$sum: 1} }});
ads_view : 500 000 documents.
this queries take 1.8s . this is its profile : https://gist.github.com/afecec63a994f8f7fd8a
indexed : db.ads_view.ensureIndex({campaign: 1});
But mongodb don't use index. Anyone know if can aggregate framework use indexes, how to index this query.
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