[Nix-dev] Incremental recompilation

[Kosyrev Serge]

Nicolas Pierron <nicolas.b.pierron at gmail.com> writes:
> Also, I admit I thought on how to solve this issue in the first place,
> but the main problem I got is not even building, this is only about
> making a copy of the source directory into the nix store.
> When your project sources are larger than 1 GB (without the VCS), you
> don't want to be reading all the bytes before being able to start any
> compilation.
>
> Thus, none of the approaches proposed before are practical for larger projects.
> So, how can we make it such that it will scale?
>
> The only approach I can think of would be to:
>  - Upload each individual file to the Nix store, when they would be needed.
>  - Make a symlink fram to re-build fake source directories.
>  - Use hash-by-content to prevent recompilation.  (when using  "gcc
> -M"  to filter out directory content, you want to make sure you get
> the same set of headers, and only cause a recompilation if some of the
> header changed)

One small nitpick:  using the global nix store for developer builds is questionable.

Global store:

  1. Shouldn't be subject to volatility inherent to developer code:
     - tens to hundreds rebuilds per day
     - hundreds to tens of thousands of objects per day
  2. Isn't GC-able by the developer, only by system administrator

If we agree, then the way to go is providing for composition of stores
-- the effective store to become a sum of system-wide and user-local stores.

-- 
с уважениeм / respectfully,
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