I am tracking some slow queries and found some odd behavior. This query (generated by Morphia) scans 20k objects and correctly returns 22 objects:

db.Example.find({ $and: [

{ lc: "eng" }

, { $or: [

{ group: "cn" }

,

{ group: "all" }

] }, { "indices.textLc":

{ $in: [ "media strengthening", "strengthening", "media" ] }

}, { wordCount:

{ $gte: 1 , $lte: 2 }

} ] }).explain();

But it has this in the indexBounds: "wordCount" : [ [1,1.7976931348623157e+308]],

This other query has the same limits and gives the same 22 objects, but only scans 4k objects:

db.Example.find( {lc: "eng" , $or: [

{ group: "cn" }

,

{ group: "all" }

], "indices.textLc":

{ $in: [ "media strengthening", "strengthening", "media" ] }

, wordCount: { $gte: 1 , $lte: 2 }}).explain();

This explain gives the same unbound max wordCount, but is obviously much faster. Is this something that can be fixed in the server or do I need to restructure all my queries?