Re: reftable: new ref storage format

From: Dave Borowitz <dborowitz@google.com>
Date: Jul 16, 2017, 21:13 UTC
Message-ID: <CAD0k6qSpNTWkn-97nQQ1DJrh=sd3dppTXytfbafqj-eVsWDTFg@mail.gmail.com>
In-Reply-To: <CAJo=hJv36tYuxHuso7NrPkfE9hApGfn=iP8g_8+MeM8L91h09g@mail.gmail.com>

On Sun, Jul 16, 2017 at 3:43 PM, Shawn Pearce <spearce@spearce.org> wrote:

Show 7 quoted lines

> True... but... in my "android" example repository we have 866,456 live
> refs. A block size of 64k needs only 443 blocks, and a 12k index, to
> get the file to compress to 28M (vs. 62M packed-refs).
>
> Index records are averaging 28 bytes per block. That gives us room for
> about 1955 blocks, or 4,574,700 refs before the index block exceeds
> 64k.

That's only a 5x increase over the current number of refs in this android repo. I would not be so sure this repo doesn't grow another 5x in the next few years. Especially as the other optimizations for working with large repos start to be applied, so it won't be prohibitively painful to work with such a repo.

Are we ok with increasing the block size when this eventually happens? (At least I think that's what we would have to do, I haven't been following closely the discussion on scaling limits.)