The shell does not set the query to {} for countDocuments() if it's empty.

i.e. the following returns an error from ADL as it is converted to a $match with no document passed in.

> db.data.countDocuments()

 

 

 

countDocuments() doesn’t seem to work with federated queries:> db.data.count()
10000
> db.data.countDocuments()
2020-06-25T00:12:36.334+0200 E QUERY [js] uncaught exception: Error: command failed: {
{{ "ok" : 0,}}
{{ "errmsg" : "failed parsing stage: $match stage must have a document as its only argument, correlationID = 161b9a7d52a6363a253a8c3e",}}
{{ "code" : 9,}}
{{ "codeName" : "FailedToParse"}}
} : aggregate failed :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:18:14
_assertCommandWorked@src/mongo/shell/assert.js:583:17
assert.commandWorked@src/mongo/shell/assert.js:673:16
DB.prototype._runAggregate@src/mongo/shell/db.js:266:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1012:12
DBCollection.prototype.countDocuments@src/mongo/shell/collection.js:1423:17
@(shell):1:1
 
18 replies

---

 

asya   8 hours ago

what happens when you run aggregate command and {$count:'c'}
 

Danilo Nobrega  8 hours ago

> db.data.aggregate({$count:‘c’})

{ “c” : 10000 }

 

Danilo Nobrega  8 hours ago

it works
 

asya   8 hours ago

that's all that the shell helper does for countDocuments
 

asya   8 hours ago

can you type db.data.countDocuments  without the () and paste what you see?
 

asya   8 hours ago

oh
 

asya   8 hours ago

I bet I know - you need to run it as db.data.countDocuments({}) I bet.
 

asya   8 hours ago

bug in the shell
 

asya   8 hours ago

query should be `query = query || {} ` same as options.
 

asya   8 hours ago

it's a bug in the shell component.
 

asya   8 hours ago

need to file a Jira ticket on it.
 

asya   8 hours ago

surprised if there isn't one already though but then why didn't we fix it?
 

Danilo Nobrega  22 minutes ago

> db.data.countDocuments
function(query, options)

{     “use strict”;     let pipeline = [

{“$match”: query}

];
    options = options || {};
    assert.eq(typeof options, “object”, “‘options’ argument must be an object”);    if (options.skip)

{         pipeline.push(

{“$skip”: options.skip}

);
    }
    if (options.limit)

{         pipeline.push(

{“$limit”: options.limit}

);
    }    // Construct an aggregation pipeline stage with sum to calculate the number of all documents.
    pipeline.push({“$group”: {“_id”: null, “n”:

{“$sum”: 1}

}});    // countDocument options other than filter, skip, and limit, are added to the aggregate command.
    let aggregateOptions = {};    if (options.hint)

{         aggregateOptions.hint = options.hint;     }

    if (options.maxTimeMS)

{         aggregateOptions.maxTimeMS = options.maxTimeMS;     }

    if (options.collation)

{         aggregateOptions.collation = options.collation;     }

    // Format cursor into an array.
    const res = this.aggregate(pipeline, aggregateOptions).toArray();
    if (res.length)

{         return res[0].n;     }

    return 0;
}
>
 

asya   21 minutes ago

Yeah it’s missing a line. Should set query to {} if it’s empty.
 

Danilo Nobrega  21 minutes ago

> db.data.countDocuments({})
10000
>