PromQL query to get the maximum of two metrics

Question

In a Prometheus timeseries database, there are two sets of data (for M1 and M2) collected with following schema

• <timestamp>, <M1> <Labels L1, L2, L3>
• <timestamp>, <M2> <Labels L1, L2, L3, L4>

Write a PromQL query that creates a new time-series N, that tracks the max(M1, M2) for each time period the query is run.

For example:

I tried using max(), but it takes only 1 argument.

Answer 1

metric1 > metric2 or metric2 > metric1

I think this does the max and works also when both metrics have the same set of labels.