README

Some helpful notes about the Prometheus connector code:

The Prometheus server URI ending in api/v1/label/__name__/values is a special URI used to list metric names which will be table names in our mapping.

Since Prometheus' metric listing endpoint, above, just lists the current metrics we treat the returned metric names as table names with known, fixed, schema.

The Prometheus metrics backing each table will not change and so the only columns need to be in the form: label VARCHAR, value DOUBLE, timestamp TIMESTAMP_WITH_TIME_ZONE

We hard code the table structure, so metadata-uri is not needed.

Splits and thus Prometheus queries are created by choosing endTime. An offset is added to make sure inclusive chunks do not overlap.

default is the name of the only schema.

The EffectiveLimits class handles predicate bounds:

We have a 2x2 matrix of responses that govern how we integrate lower or upper bounds set in the predicate versus those set by the config properties. The EffectiveLimits inner class handles the calculations around the bounds setting.

There are tests for all 4 possibilities of settings for the predicate bounds.