Method read

fdbclient/ReadYourWrites.actor.cpp:96–139

	ACTOR template <class Iter>
	static Future<Optional<Value>> read(ReadYourWritesTransaction* ryw, GetValueReq read, Iter* it) {
		// This overload is required to provide postcondition: it->extractWriteMapIterator().segmentContains(read.key)

		if (ryw->options.bypassUnreadable) {
			it->bypassUnreadableProtection();
		}
		it->skip(read.key);
		state bool dependent = it->is_dependent();
		if (it->is_kv()) {
			const KeyValueRef* result = it->kv(ryw->arena);
			if (result != nullptr) {
				return result->value;
			} else {
				return Optional<Value>();
			}
		} else if (it->is_empty_range()) {
			return Optional<Value>();
		} else {
			Optional<Value> res = wait(ryw->tr.get(read.key, Snapshot::True));
			KeyRef k(ryw->arena, read.key);

			if (res.present()) {
				if (ryw->cache.insert(k, res.get()))
					ryw->arena.dependsOn(res.get().arena());
				if (!dependent)
					return res;
			} else {
				ryw->cache.insert(k, Optional<ValueRef>());
				if (!dependent)
					return Optional<Value>();
			}

			// There was a dependent write at the key, so we need to lookup the iterator again
			it->skip(k);

			ASSERT(it->is_kv());
			const KeyValueRef* result = it->kv(ryw->arena);
			if (result != nullptr) {
				return result->value;
			} else {
				return Optional<Value>();
			}
		}
	}

	ACTOR template <class Iter>
	static Future<Key> read(ReadYourWritesTransaction* ryw, GetKeyReq read, Iter* it) {