CODEWITHSUNDEEP
mongodbsorting
Jennifer
Jennifer

Reputation: 633

MongoDB sort examine too many records on an indexed column

while using mongodb sort function I noticed that it's examining too many records, but If I didn't use sort it examine only 22 documents and returns them.

I'm trying to get users who bought some products in DESC order.

both products.userIDs and orderTime are indexed

db.collection.find({$or:[{'products.userIDs':{$in:usersArray}} , {'item.userIDs':{$in:usersArray}}]})
.sort({orderTime:-1})
.explain();

without sort it docs examined are 22 with sort docs examined are 1602

how can I sort the documents without examine too many documents.

Upvotes: 1

Views: 272

Answers (1)

klhr
klhr

Reputation: 3380

Mongo only uses a single index per query (unless there's an $or). If you want to have that particular query be well indexed, you'd want to have an index on {"products.userIDS": 1, "orderTime": 1}. That way, when it finds the documents, they'll already be sorted & it won't need to to do it in memory. The compound index docs have more details.

Upvotes: 2

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