Greetings, * Israel Brewster (ijbrewster@xxxxxxxxxx) wrote: > > On Aug 10, 2020, at 8:53 AM, Stephen Frost <sfrost@xxxxxxxxxxx> wrote: > > * Ron (ronljohnsonjr@xxxxxxxxx) wrote: > >> On 8/10/20 11:38 AM, Ravi Krishna wrote: > >>> Finally UUID results in write amplication in wal logs. Keep that in mind > >>> if your app does lot of writes. > >> > >> Because UUID is 32 bytes, while SERIAL is 4 bytes? > > > > and because it's random and so will touch a lot more pages when you're > > using it... > > I would point out, however, that using a V1 UUID rather than a V4 can help with this as it is sequential, not random (based on MAC address and timestamp + random). There is a trade off, of course, as with V1 if two writes occur on the same computer at the exact same millisecond, there is a very very small chance of generating conflicting UUID’s (see https://www.sohamkamani.com/blog/2016/10/05/uuid1-vs-uuid4/ <https://www.sohamkamani.com/blog/2016/10/05/uuid1-vs-uuid4/>). As there is still a random component, however, this seems quite unlikely. Sure, that helps, but it's still not great, and they're still much, much larger than you'd ever need for an identifier inside of a given system, so best to map it to something reasonable and avoid them as much as possible. Thanks, Stephen
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