feat(server): SCAN command add ATTR options

[lichuang]

feat(server): SCAN command add ATTR options

fix #4537

[lichuang]

@romange

for (3), (4) we need to introduce an additional flag in CompactObject to track it on keys (note that usually the flags keys are set on values).

There is TOUCHED in CompactObject, is it can be used for (3) (4)?

Another question, i want to add some python test cases, but redis.Redis scan function has only these options:

SCAN cursor [MATCH pattern] [COUNT count] [TYPE type]

(see: https://redis.io/docs/latest/commands/scan/)

[romange]

Yes, good point. We mark the keys and do it irrespective of tiering, so it should work well for this issue.
We will also need unit tests to test this behaviour.

Regarding the testing - I believe this falls well into the unit test territory, I would add the tests to generic_family_test (it is possible to use pytest redis client but I think it's just an overkill)

[lichuang]

@romange In this test case, i found that running "get" of some key, it wiil not make the key touched, so this test case failed, can you have a look what is wrong?

[romange]

it makes the key touched and you can verify it by adding debug printings for example at line db_slice.cc:624

[lichuang]

it makes the key touched and you can verify it by adding debug printings for example at line db_slice.cc:624

i see what is wrong, HasExpire() works on it->second object(which is value), while HasTouched() works on it->first object(which is key), is that expected?

[romange]

yes, this by design though I agree it's confusing.
the reason is that if you call "SADD foo bar" and then SET foo bar then all the attributes on the value (second) will be reset. if we want to preserve the attributes we should use keys (first)

[romange]

@lichuang a friendly ping :)
you almost finished, just checking if you are planning to address the comments :)

[lichuang]

@lichuang a friendly ping :) you almost finished, just checking if you are planning to address the comments :)

sorry, i am a little busy these days, i will finish it ASAP.