Re: reftable [v3]: new ref storage format

On Fri, Jul 28, 2017 at 7:18 PM, Michael Haggerty [off-list ref] wrote:

On Fri, Jul 28, 2017 at 3:12 PM, Shawn Pearce [off-list ref] wrote:

quoted

I'm with you this far, and like the {min,max}_update_index in the
header. I'm concerned about update_index in 32 bits. At some point you
need to reset the counter, or the repository is broken. 4b updates is
enough for anyone? I'd feel better about this being a 64 bit field.

Yes, I was a little bit nervous about 32 bits, too. But that's a *lot*
of updates: one per second for 136 years. If that limit were ever
reached, there could be a compaction step, where any update indices
that don't have associated reflog entries are "compacted out" of the
numerical sequence and the remaining indices are renumbered
contiguously.

I considered that, but its a bit of a pain for the writer to renumber
the remaining records.

But it's ok with me to make it 64 bits. Usually those extra bytes
would be appear as FFFFFFFF and so should prefix- and zlib-compress
well.

That was my thought. Within a single reference these will prefix
compress right out, and zlib will fix any sins within the log block at
restart points.