Just ignore matchers which match everything

[tomwilkie]

Its a common pattern to see matchers which match everything (eg instance=~".*") in queries, as people like to use multi-selects in grafana and then select "all", which results in this.

We should just ignore them - no reason to even look in the index for this matcher, it was not intersectional power.

[bboreham]

Is there an issue against Grafana not to do this?

[tomwilkie]

Not that I know of; it'd be pretty hard to implement in Grafana, as it currently doesn't manipulate the query - this is implemented as a variable substitution (ie instance=~"$instance"). Anyway I checked it out and this isn't coming from Grafana - when you select "All" in a multiselect it subs in the form a|b|c.

[bboreham]

I found one in our Grafana dashboards - there is a drop-down for pods, and the defined query is:

sum by (namespace,pod_name) (container_memory_usage_bytes{container_name!="POD",container_name!="",instance="$instance",pod_name=~"${pods:regex}"})

and when pods is set to "All" the Query Inspector shows (after decoding):

https://cloud.weave.works/api/prom/api/v1/query_range?query=sum by (namespace,pod_name) (container_memory_usage_bytes{container_name!="POD",container_name!="",instance="ip-172-20-2-42.ec2.internal",pod_name=~".+"})&start=1536745080&end=1536748680&step=30

which roughly matches what you said.

I now see why it would be hard to fix in Grafana.

[bboreham]

Wait: .+ doesn’t match everything.

[pstibrany]

I've tried to introduce this optimization in Prometheus, but it turns out it's not valid, because there are values that ".*" regex doesn't match, specifically values that include newline character.