Comment by chaz6

2 hours ago

Every time a discussion like this comes up I am reminded of Microsoft's "RID master" used in Active directory. A central server issues out chunks of ID's to each server on demand (usually when a watermark is reached), so each server always has a pool of ID's available to use.

Are there any extensions for PostgreSQL that do this?

2 comments

chaz6

Reply
tibbar  1 hour ago

This is actually a very interesting question. I assume that you are referencing extensions that add shards to Postgres, since it runs on a single server out of the box. You made me curious how those extensions/rewrites handle sequences.

It looks like Citus (one such extension that runs shards on separate workers) does something a little like what you described. Each node gets an ID, which becomes the high bits of the sequences it generates. So serial IDs are monotonic within a shard, but not across shards.

Aurora PostgreSQL Limitless uses different abstractions, but also ends up reserving different chunks of IDs for different routers to use.