Function readRangeInDb

fdbserver/KeyValueStoreShardedRocksDB.actor.cpp:516–580

};

int readRangeInDb(PhysicalShard* shard, const KeyRangeRef& range, int rowLimit, int byteLimit, RangeResult* result) {
	if (rowLimit == 0 || byteLimit == 0) {
		return 0;
	}

	int accumulatedRows = 0;
	int accumulatedBytes = 0;
	// TODO: Pass read timeout.
	const int readRangeTimeout = SERVER_KNOBS->ROCKSDB_READ_RANGE_TIMEOUT;
	rocksdb::Status s;
	auto options = getReadOptions();
	// TODO: define single shard read timeout.
	const uint64_t deadlineMircos = shard->db->GetEnv()->NowMicros() + readRangeTimeout * 1000000;
	options.deadline = std::chrono::microseconds(deadlineMircos / 1000000);

	// When using a prefix extractor, ensure that keys are returned in order even if they cross
	// a prefix boundary.
	options.auto_prefix_mode = (SERVER_KNOBS->ROCKSDB_PREFIX_LEN > 0);
	if (rowLimit >= 0) {
		ReadIterator readIter = shard->readIterPool->getIterator();
		auto cursor = readIter.iter;
		cursor->Seek(toSlice(range.begin));
		while (cursor->Valid() && toStringRef(cursor->key()) < range.end) {
			KeyValueRef kv(toStringRef(cursor->key()), toStringRef(cursor->value()));
			++accumulatedRows;
			accumulatedBytes += sizeof(KeyValueRef) + kv.expectedSize();
			result->push_back_deep(result->arena(), kv);
			// Calling `cursor->Next()` is potentially expensive, so short-circut here just in case.
			if (result->size() >= rowLimit || accumulatedBytes >= byteLimit) {
				break;
			}
			cursor->Next();
		}
		s = cursor->status();
		shard->readIterPool->returnIterator(readIter);
	} else {
		ReadIterator readIter = shard->readIterPool->getIterator();
		auto cursor = readIter.iter;
		cursor->SeekForPrev(toSlice(range.end));
		if (cursor->Valid() && toStringRef(cursor->key()) == range.end) {
			cursor->Prev();
		}
		while (cursor->Valid() && toStringRef(cursor->key()) >= range.begin) {
			KeyValueRef kv(toStringRef(cursor->key()), toStringRef(cursor->value()));
			++accumulatedRows;
			accumulatedBytes += sizeof(KeyValueRef) + kv.expectedSize();
			result->push_back_deep(result->arena(), kv);
			// Calling `cursor->Prev()` is potentially expensive, so short-circut here just in case.
			if (result->size() >= -rowLimit || accumulatedBytes >= byteLimit) {
				break;
			}
			cursor->Prev();
		}
		s = cursor->status();
		shard->readIterPool->returnIterator(readIter);
	}

	if (!s.ok()) {