private long getStoresAggregateValue(final ToLongFunction<RefDataOffHeapStore> valueFunc) {
        // It is possible this would benefit from some form of parallelism but have not used .parallel() as IO
        // is involved, so it may tie up the fork join pool
        return getAllStoresAsStream()
                .mapToLong(valueFunc)
                .sum();
    }
Get all ref stores keyed by feed name

@return Map of feedName => {@link RefDataOffHeapStore}
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/offheapstore/DelegatingRefDataOffHeapStore.java