> On Nov 5, 2020, at 10:18 AM, Mitch Gitman <mgit...@gmail.com> wrote:
>
Hi!
>
> Now, we could comfortably run all the repairs we need to within our off-hours
> window if we just left out all our tables that are insert-only. By
> insert-only, I mean that we have certain classes of tables that we're only
> inserting into; we're never updating them or deleting them. Therefore, these
> are tables that have no tombstones, and if repairs are just about clearing
> out tombstones, then ostensibly they shouldn't need to be repaired. The
> question is, is that really the case? Is there any reason to still run
> repairs on insert-only tables?
>
> If I come up with my own answer I'm satisfied with, I'll reply to myself here.
A table that never does deletes does indeed have different repair requirements.
You strictly don’t need to repair it EXCEPT to guarantee consistency when
replacing a host. If you do have a host fail, then strictly speaking you should
repair all of the replicas of the down host before you stream in the
replacement host, but that’s likely rare and this is true for all workloads and
almost nobody does it today but that’s the only real repair requirement for a
table that doesn’t have deletes.
That said: repair does help reduce differences which may reduce read repairs,
but you’re relying on consistency level for time between insert and repair
ANYWAY so it’s probably fine.
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