mongodb-indexes

I was creating my first app using MongoDB. Created index for a field, and tried a find query with $regex param, launched in a shell > db.foo.find({A:{$regex:'BLABLA!25500[0-9]'}}).explain() { "cursor" : "BtreeCursor A_1 multi", "nscanned" : 500001, "nscannedObjects" : 10, "n" : 10, "millis" : 956, "nYields" : 0, "nChunkSkips" : 0, "isMultiKey" : false, "indexOnly" : false, "indexBounds" : { "A" : [ [ "", { } ], [ /BLABLA!25500[0-9]/, /BLABLA!25500[0-9]/ ] ] } } It's very strange, because when i'm launching the same query, but with no index in collection, the performance is much better. > db

Assume a hypothetical document with 3 fields: _id : ObjectId emailAddress : string account : string Now, given a query on emailAddress AND account, which of the following two indexes will perform better: Unique index on emailAddress alone (assume it is a unique field) Compound index on account and emailAddress In terms of performance the difference will be small at best. Due to the fact that your e-mail addresses are unique any compound index that has an e-mail field will not ever be more helpful than an index on e-mail address alone. The reason for this is that your e-mail field already has

In the sparse index documentation I found note about mongodb 3.2 partial indexes Changed in version 3.2: Starting in MongoDB 3.2, MongoDB provides the option to create partial indexes. Partial indexes offer a superset of the functionality of sparse indexes. If you are using MongoDB 3.2 or later, partial indexes should be preferred over sparse indexes. Partial indexes are very helpfull and I want to use them in my project. Is it possible use them with mongoose? Angelos Veglektsis In the current Mongoose version 4.3.7 you cannot define partial indexes in the scheme, but you can still use Partial

@CompoundIndexes({ @CompoundIndex(name = "fertilizer_idx", unique = true, def = "{'name': 1, 'formula': 1, 'type': 1}") }) public class Fertilizer extends Element implements Serializable { //class stuff } Is it possible to create the index case insensitive? Right now it is differentiating from NAME to NAMe . Saving a second field lowercase (or uppercase) is not a possibility for me. Thanks, Pedro Prior of MongoDB version 3.4 we were unable to create index with case insensitive . In version 3.4 has collation option that allows users to specify language-specific rules for string comparison ,

I am performing joins in mongodb using $lookup, now i am facing a problem here. I have two collections first one to contains users all bookmarks brands and the second one contains all details about the brands.Now i am trying to return all brands details bookmarked by the user. user_bookmarked Collection {"mobile_no": "8971740148", "brands": ["5829c1df334d40e20e1d1c19", "5829c1df334d40e20e1d1c20", "5829c1df334d40e20e1d1c21"]} brands Collection {"_id": ObjectId("5829c1df334d40e20e1d1c19"), "brand_name": "Versace"} {"_id": ObjectId("5829c1df334d40e20e1d1c20"), "brand_name": "Lee Cooper"} {"_id":