Previously, Nix would not create a cache entry for substituted/cached
inputs
This led to severe slowdowns in some scenarios where a large input (like
Nixpkgs) had already been unpacked to the store but didn't exist in a
users cache, as described in https://github.com/NixOS/nix/issues/11228
Using the same method as https://github.com/NixOS/nix/pull/12911, we can
create a cache entry for the fingerprint of substituted/cached inputs
and avoid this problem entirely
These counters are extremely expensive in a multi-threaded
program. For instance, disabling them speeds up evaluation of the
NixOS/nix/2.21.2 from 32.6s to 17.8s.
With this change, the store-wide `getFSAccessor` has only one usage left
--- the evaluator. If we get rid of that (as is planned), we can then
remove that method altogether, simplifying `Store`. Hurray!
I removed the store dir by mistake from the pretty-printed (for humans)
output in eb643d034f. That change was not
supposed to change output.
This is sometimes easier / more performant to implement, and
independently it is also a more convenient interface for many callers.
The existing store-wide `getFSAccessor` is only used for
- `nix why-depends`
- the evaluator
I hope we can get rid of it for those, too, and then we have the option
of getting rid of the store-wide method.
Co-authored-by: Sergei Zimmerman <sergei@zimmerman.foo>
Old code is now just used for `nix build` --- there is no CLI breaking
change.
Test the new format, too.
The new format is not currently used, but will be used going forward,
for example in the C API.
Progress on #13570
This brings them in line with the other tests, and furthers my goals of
separating unit test data from code.
Doing this cleanup as part of my #13570 effort, but strictly-speaking,
this is separate as these data types' JSON never contained and store
paths or store dirs, just simple output name strings.
Tested by building with b_sanitize=thread and running:
nix flake prefetch-inputs --store "dummy://?read-only=false"
It might make sense to move this utility class out of dummy-store.cc,
but it seems fine for now.
No behavior is changed, just:
- Declare a canonical `nlohmnan::json::adl_serializer`
- Use `json-utils.hh` to shorten code without getting worse error
messages.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
We should use proper abstractions for reading files from the store.
E.g. this caused errors when trying to download github flakes into
an in-memory store in #14023.
The docs weren't 100% clear about bounds checking, but suggested that
errors would be caught.
The bounds checks are cheap compared to the function calls they're in,
so we have no reason to omit them.
