Re: Sequence vs UUID

On 2023-02-08 14:48:03 +0530, veem v wrote:
> So wanted to know from experts here, is there really exists any scenario in
> which UUID really cant be avoided?

Probably not. The question is usually not "is this possible" but "does
this meet the requirements at acceptable cost".

> Sequence Number = n*d+m+offset. Where n is the sequence order number, d is the
> dimensions of the multi-master replication, m ranges from 0 to n-1 is the
> number assigned to each node in the replication, and offset is the number to
> offset the sequence numbers. 

Yes, you can do this. In fact, people (including me) have already done
this.

But it's relatively easy to mess this up:

Firstly, you have to make sure that d is larger than your number of
(active) replicas will ever be, but still small enough that you will
never overflow. Probably not a problem with 64 bit sequences (if you set
d to 1E6, you can still count to 9E12 on each node), but might be a
problem if you are for some reason limited to 32 bits.

Secondly (and IMHO more importantly) you have to make sure each node
gets its own unique offset. So this needs to be ensured during
deployment, but also during migrations, restores from backups and other
infrequent events.

With random Ids you don't have to worry about this.

hp

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