Method walkDesc

ZezeJava/ZezeJava/src/main/java/Zeze/Dbh2/Dbh2.java:313–346

(Binary exclusiveStartKey, int proposeLimit, Binary prefix,
							 Action2<Binary, RocksIterator> fill)

	}

	private boolean walkDesc(Binary exclusiveStartKey, int proposeLimit, Binary prefix,
							 Action2<Binary, RocksIterator> fill) throws Exception {
		try (var it = stateMachine.getBucket().getData().iterator()) {
			if (exclusiveStartKey.size() > 0) {
				it.seekForPrev(exclusiveStartKey.copyIf());
			} else {
				// 分桶过程中，可能存在Last之后的数据，必须根据Last的情况定位，不能直接使用seekToLast。
				var lastKey = stateMachine.getBucket().getBucketMeta().getKeyLast();
				if (lastKey.size() > 0)
					it.seekForPrev(lastKey.copyIf());
				else
					it.seekToLast();
			}
			if (it.isValid()) {
				var firstKey = it.key();
				//noinspection EqualsBetweenInconvertibleTypes
				if (exclusiveStartKey.size() > 0 && exclusiveStartKey.equals(firstKey))
					it.prev(); // skip exclusive key if need.
			}

			var count = proposeLimit;
			var bucketEnd = false;
			for (; it.isValid() && count > 0; it.prev(), count--) {
				var key = new Binary(it.key());
				if (prefix.size() > 0 && !key.startsWith(prefix)) {
					bucketEnd = true;
					break;
				}
				fill.run(key, it);
			}

			return bucketEnd || !it.isValid();
		}
	}

	private boolean walk(Binary exclusiveStartKey, int proposeLimit, boolean desc, Binary prefix,
						 Action2<Binary, RocksIterator> fill) throws Exception {