Dex doesn't recommend indexes when sort operation is provided

[Sirtea]

Having the following collection:

> db.people.find()
{ "_id" : ObjectId("52779d40ad2f74e0deb3a7cf"), "name" : "Gerard", "age" : 31 }
{ "_id" : ObjectId("52779d83ad2f74e0deb3a7d0"), "name" : "Rose", "age" : 23 }
{ "_id" : ObjectId("52779d9ead2f74e0deb3a7d1"), "name" : "Yuki", "age" : 30 }
> 

I tried some basic queries, for example:

> db.people.find({age:{$gte:30}}).sort({name:1})
> db.people.find({age:{$gte:30}})

Passing the DEX tool to an empty system.profile collection, I can see that there's a suggestion when issuing the second query, but not when using the first one.

With sort operation:

> db.system.profile.drop()
true
> db.setProfilingLevel(2)
{ "was" : 0, "slowms" : 100, "ok" : 1 }
> db.people.find({age:{$gte:30}}).sort({name:1})
{ "_id" : ObjectId("52779d40ad2f74e0deb3a7cf"), "name" : "Gerard", "age" : 31 }
{ "_id" : ObjectId("52779d9ead2f74e0deb3a7d1"), "name" : "Yuki", "age" : 30 }
> db.setProfilingLevel(0)
{ "was" : 2, "slowms" : 100, "ok" : 1 }
> 

(env)gerard@antares:~/projects/dextest$ dex -p mongodb://localhost/test
{
    'runStats': {
        'linesRecommended': 0, 
        'linesProcessed': 1, 
        'linesPassed': 2
    }, 
    'results': []
}
(env)gerard@antares:~/projects/dextest$ 

Without sort operation:

> db.system.profile.drop()
true
> db.setProfilingLevel(2)
{ "was" : 0, "slowms" : 100, "ok" : 1 }
> db.people.find({age:{$gte:30}})
{ "_id" : ObjectId("52779d40ad2f74e0deb3a7cf"), "name" : "Gerard", "age" : 31 }
{ "_id" : ObjectId("52779d9ead2f74e0deb3a7d1"), "name" : "Yuki", "age" : 30 }
> db.setProfilingLevel(0)
{ "was" : 2, "slowms" : 100, "ok" : 1 }
> 

(env)gerard@antares:~/projects/dextest$ dex -p mongodb://localhost/test
{
    'runStats': {
        'linesRecommended': 1, 
        'linesProcessed': 1, 
        'linesPassed': 2
    }, 
    'results': [
        {
            'queryMask': '{"$query":{"age":{"$gte":"<val>"}}}', 
            'namespace': 'test.people', 
            'recommendation': {
                'index': '{"age": 1}', 
                'namespace': 'test.people', 
                'shellCommand': 'db["people"].ensureIndex({"age": 1}, {"background": true})'
            }, 
            'details': {
                'count': 1, 
                'totalTimeMillis': 0, 
                'avgTimeMillis': 0
            }
        }
    ]
}
(env)gerard@antares:~/projects/dextest$ 

[esedor]

Thanks for this detailed report! I'll take a look. One question: Are you working with the HEAD of this Dex repo, or the last release of Dex on pypi?

[Sirtea]

Not sure, it was the pypi version, installed via pip in a virtualenv

(env)gerard@antares:~/projects/dextest$ pip freeze
Dex==0.6
PyYAML==3.10
argparse==1.2.1
dargparse==0.2.3
ordereddict==1.1
pymongo==2.6.3
wsgiref==0.1.2
(env)gerard@antares:~/projects/dextest$ 

[srlowe]

Any update on this? I'm having the same issue