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[Nicolae Brinza <nbrinza@xxxxxxxxx>]

> I don't understand why. In my example it wouldn't. The count functions could
> count
> the number of empty objects or objects that contain only the STREET field.

I've looked into the test and here are the issues:
1) The fn:count() does not have the %explores-json annotation. I've confused it with the JSONiq array size() function.

2) Currently the dataguide does not distinguish between any of the fn: functions. So for example if you modify the query:

    for $obj in parse-json(f:read-text(fn:resolve-uri("citylots-small.json")))
    group by $s := $obj.STREET
    return {
      street : $s,
      count : count($obj),
      seq : subsequence($obj, 1, 100)
    }

then if you prune the input to have only the .STREET field you'll get an incorrect result. So currently the argument to subsequence() is "explored" and so the dataguide is "*" in this case. The same happens with count(). 

3) fn:count() is a special case as it only cares for the number of objects and not their contents. I think another annotation could be added, which would be the opposite of %explores-json and which would indicate that the function ignores the details of the object. Or I could just add some code in the dataguide collection to handle fn:count() separately. 

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