On Thu, Jul 7, 2011 at 2:36 AM, Philip Martin
<philip.martin_at_wandisco.com> wrote:
>
> r0 revprops are a concern, they can have different access patterns. For
> example a master/slave setup running svnsync once per revision (a common
> setup) will write the r0 pack file several times per revision. We don't
> want the pack file to become the dominant IO.
>
> I wonder if we could offset the shard boundaries, so that r0 is the last
> revision in the first shard and r1-rN is the second shard. Then r0
> would be a shard on its own and the r0 pack file would be much smaller.
> We would have to repack the repository on upgrade but the code changes
> for this could be small, just +/-1 in a few places.
Changing the offsets for all the shard boundaries is just asking for
trouble, as it would mean that revision shards and revprop shards
wouldn't match up. That seems like a pretty big "gotcha".
Instead, we could just special-case r0 revprops so that they never get
packed, and that the 0th shard includes r1:rN, instead of r0:rN. That
would only impact the 0th shard, rather than every revprop shard.
-Hyrum
Received on 2011-07-07 15:30:07 CEST