private void checkLegacyStoreState() {
        LOGGER.debug("checkLegacyStoreState()");
        final RefDataOffHeapStore legacyStore = this.legacyRefDataStore;
        if (legacyStore != null) {
            if (legacyStore.isEmpty()) {
                // Purge may have cleaned it out, so don't need to check for migrations in future
                if (LOGGER.isDebugEnabled()) {
                    if (migrationCheckRequired) {
                        LOGGER.debug("Setting migrationCheckRequired to false");
                    }
                }
                migrationCheckRequired = false;
            }
        } else {
            migrationCheckRequired = false;
        }
    }
@return The count of feed stores initialised, 1 or 0.
stroom-pipeline/src/main/java/stroom/pipeline/refdata/store/offheapstore/DelegatingRefDataOffHeapStore.java