long getValueStoreCount() {
        return valueStore.getEntryCount();
    }
Get an instance of a {@link RefDataLoader} for bulk loading multiple entries for a given
{@link RefStreamDefinition} and its associated effectiveTimeMs. The {@link RefDataLoader}
should be used in a try with resources block to ensure any transactions are closed, e.g.
<pre>try (RefDataLoader refDataLoader = refDataOffHeapStore.getLoader(...)) { ... }</pre>
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/offheapstore/RefDataOffHeapStore.java