Influxdb: [feature request] Querying only based on tag

[jgrobelny-dev]

Hi. It just occurred to me that I cant get tag values using standard field syntax.
Typically i use :
SELECT <field key> FROM <measurement>
To do the same with tags (which are no more then indexed fields suppose) I have to :
SHOW TAG VALUES FROM "measurement_name" WITH KEY = "tag_key"
It gives more or less the same result (not including timestamp with tag values). Why can't we ask for tag values with a simple SELECT query?
It's not a bug nor a important fix but I think some stuff could get streamlined with SELECT working on tags.

[rossmcdonald]

@groblus I'm not sure I follow. You can query for tags just as you can with fields. For example:

> select time,branch,cpu,usage_user from telegraf."default".cpu where time > now() - 10d LIMIT 10
name: cpu
---------
time            branch      cpu     usage_user
1453835530000000000 meta-service2   cpu-total   34.863773965690996
1453835530000000000 meta-service2   cpu1        61.663286004052416
1453835530000000000 meta-service2   cpu-total   0
1453835530000000000 meta-service2   cpu-total   59.26113360322834
1453835530000000000 meta-service2   cpu0        56.86868686869006
1453835530000000000 meta-service2   cpu1        0
1453835530000000000 meta-service2   cpu1        36.46464646464574
1453835530000000000 meta-service2   cpu0        33.400605449041315
1453835530000000000 meta-service2   cpu0        0
1453835540000000000 meta-service2   cpu0        27.923387096776366

branch and cpu are tags, and usage_user is a field. Is that what you mean?

[jgrobelny-dev]

@rossmcdonald Try to make a query with only cpu - it won't work.
Server returned error: statement must have at least one field in select clause
When you combine fields with tags in a query then it's ok.
Additionally you can't make things like counting number of tag values (DISTINCT also works only on fields).
And little off topic - is there any way of counting resulting rows (not only by checking non empty field values), something like:
SELECT count(*) FROM cpu ?

[rossmcdonald]

@groblus Ah, got it. Thank you for clarifying. Regarding:

Additionally you can't make things like counting number of tag values (DISTINCT also works only on fields).

You can add a GROUP BY <tag> which will display all of the different tags, but you are right that it doesn't quite enable you to count the different tag values in an efficient manner. Regarding:

And little off topic - is there any way of counting resulting rows (not only by checking non empty field values), something like: SELECT count(*) FROM cpu ?

I'm not aware of a way to do that inside the query language, unfortunately. You can do something similar using a non-interactive query, though:

influx -execute "select * from cpu" -database "telegraf" | sed '/name: .*/d' | sed '/\-\-/d' | sed '/^$/d' | wc -l

Not ideal, but it can get you closer.

[beckettsean]

If https://github.com/influxdata/influxdb/issues/3040 and https://github.com/influxdata/influxdb/issues/5668 were implemented it would address all the issues here, without changing the fundamental constraints on the SELECT clause.

[joe-spanning]

We would also like to see this implemented.

[dwalton76]

Any update on this one?

[denniswalker]

+1

[ExplodingCabbage]

Yeah, having to include an arbitrary field you don't need in your query in order to make it return results is bonkers. I presume there's no deep technical limitation preventing InfluxDB from supporting SELECT tag1, tag2, time FROM measurement (since I don't see how it can be any harder than SELECT tag1, tag2, arbitrary_field, time FROM measurement, which does return results), so it should just be made to work.

[kMeillet]

Any news ?

[sykobee]

Use an inner select - here's a variable definition I have in Grafana+InfluxDB:

SELECT "flow" FROM (SELECT last("value"), "flow" FROM amq_active WHERE "flow" != 'Master' AND "environment" =~ /$environment/ AND time > now() - 5m GROUP BY "flow")

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