VM returns different result than Prometheus

[phantasia15]

Describe the bug
group_left(labels) seems to take labels from the "many" side while it should take from the "one" side

To Reproduce

label_replace(
                kube_pod_owner{job="kube-state-metrics", owner_kind="ReplicaSet"},
                "replicaset", "$1", "owner_name", "(.*)"
 ) * on(replicaset, namespace) group_left(owner_name) kube_replicaset_owner{job="kube-state-metrics"}

VM currently returns wrong owner_name value:

{namespace=dev, pod=flight-9df5c6f9c-7dgkf, owner_name=flight-9df5c6f9c}

Expected behavior
Basically, both the left & right side of the binary operator contain "owner_name" label but with different values. Since I specify group_left(owner_name), the owner_name of the right side should take priority in the output.

Here is the result of the left side:

{namespace=dev, pod=flight-9df5c6f9c-7dgkf, owner_name=flight-9df5c6f9c, owner_kind=Replicaset, replicaset=flight-9df5c6f9c}

The result of the right side:

{namespace=dev, replicaset=flight-9df5c6f9c, owner_name=flight, owner_kind=Deployment}

The Prometheus docs here also states that the labels in group_left(labels) should be taken from "one" side. So VM should return this instead (it is also what Prometheus returns):

{namespace=dev, pod=flight-9df5c6f9c-7dgkf, owner_name=flight}

Version
The line returned when passing --version command line flag to binary.

victoria-metrics-20200620-223134-tags-v1.37.2-0-ge149019c0

[valyala]

Confirmed that VictoriaMetrics doesn't override owner_name label value from the left side with the value from right side. This differs from Prometheus behavior, which can be inspected by the following links:

• empty group_left list - Prometheus uses owner_name from the left side
• group_left(owner_name) - Prometheus uses owner_name from the right side.

This bug will be fixed soon.

[valyala]

The bug should be fixed in the commit 7532dbc . @phantasia15 , could you buld VictoriaMetrics from this commit according to the instructions and verify whether the bug is fixed there?

[phantasia15]

@valyala Confirmed that the bug is fixed with the above commit.
Thank you very much!

[valyala]

@phantasia15 , thanks for the confirmation.

Re-opening the issue until the bugfix is included in the next release.

[valyala]

The bugfix has been included in v1.37.3. Closing the issue as fixed.