b) ID-s weren’t integers but GUID-s?
You can try uuid_hash if you’ve got UUIDs on Postgres:
select mod(mod(uuid_hash(gen_random_uuid()), 10) + 10, 10);
Note the awkward mod(mod(thing, x) + x, x) form that took. That’s because Postgres’s native mod functionality, annoyingly, can return negative values: https://stackoverflow.com/a/32402428/5932228.
If you’re using auto incrementing keys then it is more or less sequential. If you’re splitting into N partitions, you would need a delete pattern that favored one specific value of N more than others. As I said in the earlier post it’s trivial to just go query your database to see if that is happening in your case: select id % 10, count(id) from table group by 1.
@billylanchantin is dead on with the uuid answer. Basically what we’re using % here for is a kind of “consistent hash” which reliably turns a given input value into one of a smaller set of output values. % is a very efficient way of doing this for integers, but there are other consistent hashing functions that work on other values too.