Question

**
UPDATE
**

I posted an answer as it’s been confirmed to be an issue

**
ORIGINAL
**

First, I apologize — I have just started using MongoDB yesterday, and I am still pretty new at this. I have a pretty simple query, and using PHP my findings are this:

Mongo version is 2.0.4, running on CentOS 6.2 (Final) x64

$start = microtime(true);
$totalactive = $db->people->count(array('items'=> array('$gt' => 1)));
$end = microtime(true);
printf("Query lasted %.2f seconds\n", $end - $start);

Without index, it returns:

Query lasted 0.15 seconds

I have 280,000 records in people the database. So I thought adding an index on “items” should be helpful, because I query this data a lot. But to my disbelief, after adding the index I get this:

Query lasted 0.25 seconds

Am I doing anything wrong?

Instead of count i used find to get the explain and this is the output:

> db.people.find({ 'items' : { '$gte' : 1 } }).explain();
{
"cursor" : "BtreeCursor items_1",
"nscanned" : 206396,
"nscannedObjects" : 206396,
"n" : 206396,
"millis" : 269,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
    "items" : [
        [
            1,
            1.7976931348623157e+308
        ]
    ]
}
}

If I change my query to be “$ne” 0, it takes 10ms more!

Here are the collection stats:

> db.people.stats()
{
"ns" : "stats.people",
"count" : 281207,
"size" : 23621416,
"avgObjSize" : 84.00009957077881,
"storageSize" : 33333248,
"numExtents" : 8,
"nindexes" : 2,
"lastExtentSize" : 12083200,
"paddingFactor" : 1,
"flags" : 0,
"totalIndexSize" : 21412944,
"indexSizes" : {
    "_id_" : 14324352,
    "items_1" : 7088592
},
"ok" : 1
}

I have 1GB of ram free, so I believe the index fits in memory.

Here’s the people index, as requested:

> db.people.getIndexes()
[
{
    "v" : 1,
    "key" : {
        "_id" : 1
    },
    "ns" : "stats.people",
    "name" : "_id_"
},
{
    "v" : 1,
    "key" : {
        "items" : 1
    },
    "ns" : "stats.people",
    "name" : "items_1"
}
]

Answer 1

This was confirmed to be a bug or something that needed optimization in the MongoDB engine. I posted this in the mongo mailing list and the response I received from Eliot Horowitz

That’s definitely a bug, or at least a path that could be way better
optimized. Made a case: https://jira.mongodb.org/browse/SERVER-5607

Priority:  Major
Fix Version/s: 2.3 desired
Type:  Bug

Thanks for those who helped confirming this was a bug =)