private void internalRegionDelete(final Region region, final List<byte[]> subKeys,
                                      final CompletableFuture<Boolean> future, final int retriesLeft,
                                      final Errors lastCause) {
        final RegionEngine regionEngine = getRegionEngine(region.getId(), true);
        final RetryRunner retryRunner = retryCause -> internalRegionDelete(region, subKeys, future,
                retriesLeft - 1, retryCause);
        final FailoverClosure<Boolean> closure = new FailoverClosureImpl<>(future, false, retriesLeft,
                retryRunner);
        if (regionEngine != null) {
            if (ensureOnValidEpoch(region, regionEngine, closure)) {
                final RawKVStore rawKVStore = getRawKVStore(regionEngine);
                if (this.kvDispatcher == null) {
                    rawKVStore.delete(subKeys, closure);
                } else {
                    this.kvDispatcher.execute(() -> rawKVStore.delete(subKeys, closure));
                }
            }
        } else {
            final BatchDeleteRequest request = new BatchDeleteRequest();
            request.setKeys(subKeys);
            request.setRegionId(region.getId());
            request.setRegionEpoch(region.getRegionEpoch());
            this.rheaKVRpcService.callAsyncWithRpc(request, closure, lastCause);
        }
    }
Returns a heap-allocated iterator over the contents of the
database.
<p>
Caller should close the iterator when it is no longer needed.
The returned iterator should be closed before this db is closed.
<p>
<pre>
    KVIterator it = unsafeLocalIterator();
    try {
        // do something
    } finally {
        it.close();
    }
<pre/>
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/client/DefaultRheaKVStore.java