min() / max() with descending order sort not working

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    • Type: Bug
    • Resolution: Duplicate
    • Priority: Major - P3
    • None
    • Affects Version/s: 2.4.3, 2.4.7
    • Component/s: Querying
    • ALL
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    • 3
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      Setting the .min() or .max() explicitly on a find and using a descending sort seems not to work. 

      > db.docs.drop()
> for (var i=0; i<10; i++) { db.docs.insert({number: i}) }
> db.docs.ensureIndex({number: 1})

      no sort

      > db.docs.find().max({number: 4})
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e3"), "number" : 0 }
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e4"), "number" : 1 }
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e5"), "number" : 2 }
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e6"), "number" : 3 }

      ascending sort

      > db.docs.find().max({number: 4}).sort({number: 1})
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e3"), "number" : 0 }
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e4"), "number" : 1 }
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e5"), "number" : 2 }
{ "_id" : ObjectId("51834d678d284e5c5e3ea7e6"), "number" : 3 }

      descending sort

      > db.docs.find().max({number: 4}).sort({number: -1})
>

      I would expect to get the 4 documents back in the 'reverse order' case, in number order: 3, 2, 1, 0. Instead, I get 0 documents back.

      explain of ascending sort

      > db.docs.find().max({number: 4}).sort({number: 1}).explain()
{
	"cursor" : "BtreeCursor number_1",
	"isMultiKey" : false,
	"n" : 4,
	"nscannedObjects" : 4,
	"nscanned" : 4,
	"nscannedObjectsAllPlans" : 4,
	"nscannedAllPlans" : 4,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 0,
	"nChunkSkips" : 0,
	"millis" : 0,
	"indexBounds" : {
		"start" : {
			"number" : {
				"$minElement" : 1
			}
		},
		"end" : {
			"number" : 4
		}
	},
	"server" : "capslock.local:27017"
}

      explain of descending sort

      > db.docs.find().max({number: 4}).sort({number: -1}).explain()
{
	"cursor" : "BtreeCursor number_1 reverse",
	"isMultiKey" : false,
	"n" : 0,
	"nscannedObjects" : 0,
	"nscanned" : 0,
	"nscannedObjectsAllPlans" : 0,
	"nscannedAllPlans" : 0,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 0,
	"nChunkSkips" : 0,
	"millis" : 0,
	"indexBounds" : {
		"start" : {
			"number" : {
				"$minElement" : 1
			}
		},
		"end" : {
			"number" : 4
		}
	},
	"server" : "capslock.local:27017"
}

        1. server9547.js
          0.5 kB

            Assignee:
            Ian Whalen (Inactive)
            Reporter:
            Thomas Rueckstiess (Inactive)
            Votes:
            3 Vote for this issue
            Watchers:
            6 Start watching this issue

              Created:
              Updated:
              Resolved: