Re: Why unrelated package trigger rebuild?

[Christopher Baines]

zimoun <zimon.toutoune@gmail.com> writes:

> Dear,
>
> From the Data Service:
>
> <https://data.guix.gnu.org/repository/1/branch/master/package/ghc-haddock/output-history>
>
> the commit 39222080911eaf3d7f74effe4467c1a04464aef3 which is about the
> addition of the package ’dkgpg’ modifies the hash of the package
> ’ghc-haddock’ from:
>
>   /gnu/store/s7s3ksfhkdbb6k6si8bjnxy8vvywv322-ghc-haddock-2.22.0
>
> to:
>
>   /gnu/store/j5llszq1cf12qn79bvhc042wc06ibfix-ghc-haddock-2.22.0
>
> Well, I miss why the addition of one package changes the hash of another
> unrelated one?  Is it expected?

I think the first thing to spot is that the Guix Data Service does a
poor job of showing what happened. If you look at the 3 outputs that
start or end in July (07), the pattern isn't a neat "one after the
other".

What I think actually happens is that:

 - 2020-06-13 21:04:16:       hash begins lw2
 - 2020-07-21 21:57:03:       hash begins s7s
 - after 2020-07-21 21:57:03: hash goes back to beginning lw2
 - 2020-07-24 12:22:11:       hash begins j5l

I think one of the implicit assumptions the query for that page makes,
is that the outputs don't really repeat, and in this case, that doesn't
hold. I think there's room for improvement to try and correct that.

Sorry about that,

Chris