public int partition() {
        return partition;
    }
A cached share partition. The broker maintains a set of these objects for each share session.
<p>
We store many of these objects, so it is important for them to be memory-efficient.
That is why we store topic and partition separately rather than storing a TopicPartition
object. The TP object takes up more memory because it is a separate JVM object, and
because it stores the cached hash code in memory.
server/src/main/java/org/apache/kafka/server/share/CachedSharePartition.java