void addKnownMapNames(final RefDataStore refDataStore,
                          final RefStreamDefinition refStreamDefinition) {

        if (!refStreamDefToMapNamesMap.containsKey(refStreamDefinition)) {
            final Optional<ProcessingState> optLoadState = refDataStore.getLoadState(
                    refStreamDefinition);

            // Make sure the load was good
            if (optLoadState.filter(ProcessingState.COMPLETE::equals).isPresent()) {
                final Set<String> mapNames = refDataStore.getMapNames(refStreamDefinition);

                // Debug as should only be done once per stream
                LOGGER.debug(() -> LogUtil.message(
                        "Putting mapNames: {} for refStreamDefinition: {}",
                        mapNames,
                        refStreamDefinition));

                refStreamDefToMapNamesMap.put(refStreamDefinition, mapNames);
            } else {
                LOGGER.trace("Load not complete, optLoadState: {}", optLoadState);
            }
        } else {
            LOGGER.trace(() -> LogUtil.message("RefStreamDefinition {} already known, available maps: {}",
                    refStreamDefinition, refStreamDefToMapNamesMap.get(refStreamDefinition)));
        }
    }
Cache the set of map names known to exist in this {@link RefStreamDefinition}.
stroom-pipeline/src/main/java/stroom/pipeline/refdata/RefDataStoreHolder.java