0

I've was recently reading an article around how Instgram used to shard their IDs and they use a unique function to generate ids on their servers https://instagram-engineering.com/sharding-ids-at-instagram-1cf5a71e5a5c

But it got me curious around whether if you could just assign a shard to a particular user rather than every item and how performant it would be. Especially in a large scale website.

So would a function similar to the following be a valid approach.

Assuming a users table on a dedicated database purely for users.

User - UID - name - shardId

Where shardId is calculated via a function that starts at 1, and for every new insert it would increment - upto a max of n (say 2048) for this example. Then reset to 1. Almost acting as a round robin to distribute users data among a shards.

Would there be serious performance implications to such a function, especially during high load? As serial columns simply select a nextval from a sequence do they not? It's just an extra step of reseting a sequence once it reaches n. Or am I barking up the wrong tree?

1 Answer 1

0

As serial columns simply select a nextval from a sequence do they not? It's just an extra step of reseting a sequence once it reaches n

Not even an extra step because cycling is a built-in functionality of sequences, See CREATE SEQUENCE.

Example:

=> create sequence s maxvalue 5 cycle;

=> select nextval('s') from generate_series(1,7);
 nextval 
---------
       1
       2
       3
       4
       5
       1
       2

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.