implement COPY

[adiholden]

https://redis.io/docs/latest/commands/copy/

[MahendraDani]

@adiholden I would like to work on this issue.
Would you please tell me how should I approach this issue?

[chakaz]

@MahendraDani thanks for your interest in contributing to Dragonfly!
I'd take a look at the MOVE command implementation (here) and do something similar, without the removal of the original key.

[MahendraDani]

@chakaz Is there any guide for setting up the project locally?

[chakaz]

https://github.com/dragonflydb/dragonfly/blob/main/docs/build-from-source.md

[sanathkandikanti]

Hi, I have a question about the debug check in db_slice.cc

dragonfly/src/server/db_slice.cc

Line 978 in 851e432

DCHECK(!obj.IsRef());

From what I understand, AsRef() creates a copy of the original object using memcpy, even though its name suggests it returns a reference. Given this implementation, is this debug validation necessary?

dragonfly/src/core/compact_object.h

Line 178 in 851e432

memcpy(&res.u_, &u_, sizeof(u_));

CC: @chakaz @adiholden @romange

[chakaz]

Hi @sanathkandikanti, line 978 you quoted here is merely a DCHECK (i.e. checks an assumption in debug builds) to make sure obj is a reference, it's not calling AsRef(). Did I misunderstood you?