PartiallyOrdered

Represents the mathematical concept of partial ordering. Unlike Comparable, the compareTo method can return null when the two elements don't have a natural ordering.

We use this interface to compare CDC positions to see when we have reached the target offset or to determine whether we are still making progress. We need partial ordering rather than a full ordering like Comparable because sometimes we are missing some fields in the offset and can't determine whether one offset is beyond another. In these cases, we typically continue until we encounter a fully populated offset.

The supplied convenience methods handle the null checking and allow us to make these kinds of comparisons ergonomically.