Method get

fdbclient/NativeAPI.actor.cpp:5198–5256

}

Future<Optional<Value>> Transaction::get(const Key& key, Snapshot snapshot) {
	++trState->cx->transactionLogicalReads;
	++trState->cx->transactionGetValueRequests;
	// ASSERT (key < allKeys.end);

	// There are no keys in the database with size greater than the max key size
	if (key.size() > getMaxReadKeySize(key)) {
		return Optional<Value>();
	}

	auto ver = getReadVersion();

	/*	if (!systemKeys.contains(key))
	        return Optional<Value>(Value()); */

	if (!snapshot)
		tr.transaction.read_conflict_ranges.push_back(tr.arena, singleKeyRange(key, tr.arena));

	UseTenant useTenant = UseTenant::True;
	if (key == metadataVersionKey) {
		// It is legal to read the metadata version key inside of a tenant.
		// This will return the global metadata version key.
		useTenant = UseTenant::False;
		++trState->cx->transactionMetadataVersionReads;
		if (!ver.isReady() || metadataVersion.isSet()) {
			return metadataVersion.getFuture();
		} else {
			if (ver.isError()) {
				return ver.getError();
			}
			if (ver.get() == trState->cx->metadataVersionCache[trState->cx->mvCacheInsertLocation].first) {
				return trState->cx->metadataVersionCache[trState->cx->mvCacheInsertLocation].second;
			}

			Version v = ver.get();
			int hi = trState->cx->mvCacheInsertLocation;
			int lo = (trState->cx->mvCacheInsertLocation + 1) % trState->cx->metadataVersionCache.size();

			while (hi != lo) {
				int cu = hi > lo ? (hi + lo) / 2
				                 : ((hi + trState->cx->metadataVersionCache.size() + lo) / 2) %
				                       trState->cx->metadataVersionCache.size();
				if (v == trState->cx->metadataVersionCache[cu].first) {
					return trState->cx->metadataVersionCache[cu].second;
				}
				if (cu == lo) {
					break;
				}
				if (v < trState->cx->metadataVersionCache[cu].first) {
					hi = cu;
				} else {
					lo = (cu + 1) % trState->cx->metadataVersionCache.size();
				}
			}
		}
	}

	return getValue(trState, key, ver, useTenant);