@Override
    public long getRangeValueEntryCount() {
        return rangeValueNestedMap.entrySet()
                .stream()
                .mapToLong(entry -> entry.getValue().size())
                .sum();
    }
A heap based implementation of the {@link RefDataStore}
that is intended for use with reference data with a very short life, i.e. context
data that is transient and only required for the life of a single pipeline processor
task. As such it is not thread safe and only intended to be used to by a single thread.
It also does not support purge operations as it is expected that the store will be created,
populated, used, then destroyed when no longer needed.
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/onheapstore/RefDataOnHeapStore.java