querying not empty tag value in v0.10

[RoCat]

Hi,
I have a db with one measurement and multiple tags

For some reasons, sometimes one of these tags is set and sometimes it isn't (I don't know if it is null or empty or '' or something else)

If I request my measurement with
select distinct(hit) from myMeasurement group by myTag
here is the answer:

name: myMeasurement
tags: myTag=
time    distinct
----    --------
0   [1]


name: myMeasurement
tags: myTag=http://exemple.com/samples/coca.png
time    distinct
----    --------
0   [1]

I cannot figure out how to query only if these tag value is set.
I use InfluxDB v0.10.3 (git: 0.10.0 f55169e, built 2016-03-09T17:13:16.236131) and Isaw that since influxDB 0.9 we cannot have null value, so I assume it is not null but something else.
I tried:
where myTag <> null
where myTag <> ''
where myTag

The only way to get what I want is
where myTag =~ //

But this seems not a good solution to me, not sure about how index are used with such regexp.
I'm not sure it is a bug but it seems strange to me to have kind of null values and cannot query them in the same time.

[RoCat]

seems to be duplicate of
#6283