@Override
    public synchronized void clear() {
        try {
            close();
            env.delete();
        } finally {
            resultCount.set(0);
            totalResultCount.set(0);
        }
    }
Clear the data store.
Synchronised with get() to prevent a shutdown happening while reads are going on.
stroom-query/stroom-query-common/src/main/java/stroom/query/common/v2/LmdbDataStore.java