Create stream consumer group will make the xread command error

[jihuayu]

Search before asking

• I had searched in the issues and found no similar issues.

Version

unstable

Minimal reproduce step

XADD test * a a
XGROUP create test test 0
xread STREAMS test 0

What did you expect to see?

1) 1) "test"
   2) 1) 1) "1708506496723-0"
         2) 1) "a"
            2) "a"

What did you see instead?

(error) ERR Invalid argument: failed to decode stream entry value

Anything Else?

I discovered this when developing the xreadgroup command.

The subkey of the consumer group overlapped with the subkey of the stream entry.
This causes the range function to get the stream Entry with the group's subkey.

I think there is something wrong with the subkey design of the consumer & consumer group metadata.

kvrocks/src/types/redis_stream.cc

Lines 168 to 176 in 30f6bee

	std::string Stream::internalKeyFromGroupName(const std::string &ns_key, const StreamMetadata &metadata,
	const std::string &group_name) const {
	std::string sub_key;
	PutFixed64(&sub_key, group_name.size());
	sub_key += group_name;
	sub_key += consumerGroupMetadataDelimiter;
	std::string entry_key = InternalKey(ns_key, sub_key, metadata.version, storage_->IsSlotIdEncoded()).Encode();
	return entry_key;
	}

I don't really understand why we puts the consumerGroupMetadataDelimiter at the end of the subkey. Shouldn't we put it at the start?

Are you willing to submit a PR?

• I'm willing to submit a PR!

[Yangsx-1]

Good catch! I'm still working on XREADGROUP and will finish it in a few days, and this bug may caused by no subkey identification in the original stream commands. :(

[jihuayu]

@Yangsx-1 Thank you. I have fixed this bug, please review it.