Add support of the command COPY

[PragmaTwice]

Refer to https://redis.io/commands/copy/

[Qiaolin-Yu]

I want to try. Can you assign this to me?

[PragmaTwice]

Sure! Assigned.

[Qiaolin-Yu]

May I know where I should write my unit tests?

[git-hulk]

@Qiaolin-Yu It's good to add Go tests only.

[Qiaolin-Yu]

By the way, for the optional part [DB destination-db], what should I do to write the KV to the destination-db? Should I use RedisWriter::selectDB to implement?

[MaheshMadushan]

Hi @Qiaolin-Yu , according to my observation KVROCKS doesn't have DB instead you can use namespace concept. Please verify with @git-hulk and @PragmaTwice

[git-hulk]

@MaheshMadushan You're right. The RENAME command also has similar issue, so we can use the namespace in those commands.

[jihuayu]

@MaheshMadushan You're right. The RENAME command also has similar issue, so we can use the namespace in those commands.

@git-hulk Maybe not the RENAME command, but the MOVE command

[git-hulk]

@jihuayu Sorry for the wrong information. Yes, that's MOVE command instead of RENAME.

[Chiro11]

By the way, for the optional part [DB destination-db], what should I do to write the KV to the destination-db? Should I use RedisWriter::selectDB to implement?

@Qiaolin-Yu Hi, are you still working on this issue?

[Chiro11]

@git-hulk I think you can assign it to me now 'cause he hasn't responded for two months. This cmd is similar to MOVE and RENAME, suitable for me.

[git-hulk]

@Chiro11 Thank you!

[Chiro11]

@git-hulk To adapt to kvrocks, it may need to make minor modifications. redis ver: COPY source destination [DB destination-db] [REPLACE] I think we can replace 'DB' with 'NS'/'NAMESPACE'/'TO', or keep it, and replace destination-db to token. What do you think?

[git-hulk]

@Chiro11 Perhaps we can support the [DB](DB must be 0) first and copy between namespaces should be implemented as COPYX.