Re: Guix pull: avoiding "Computing Guix derivation"

[Edouard Klein]

Hi,


Josselin Poiret <dev@jpoiret.xyz> writes:

> [[PGP Signed Part:Undecided]]
> Hi everyone,
>
> Edouard Klein <edou@rdklein.fr> writes:
>
>> I think my misunderstanding boils down to a bad mental model of how guix
>> works.
>>
>> What I imagine the "Computing guix derivation" step to be is no
>> different than building a package whose inputs are the channels'
>> sources, guile, and the current guix, and whose output is the new guix.
>>
>> Simon and Richard pointed out that the combinatorial combination of all
>> possible input combination makes this hard to substitute, but I don't
>> understand how its result, once in the store, can't lead to a simple
>> linking from the profile to the store, instead of re-running the
>> "Computing guix derivation" step when guix pull is called with the same
>> inputs.
>>
>> Surely my mental model is wrong somehow ?
>
> You might be interested in this thread [1], which tries to explain the
> terrible performance of `guix pull`.
>
> [1] mid:87wmxe3vsa.fsf@jpoiret.xyz
>     https://yhetil.org/guix/87wmxe3vsa.fsf@jpoiret.xyz/
>

I reread it, but I still don't understand why this step is not
substitutable. It has a fixed set of input and it is a deterministic
process. Unless I don't understand what is going on, which is probable,
but I can't seem to find where I'm mistaken.



> Best,