This was already optimised before, but profiling found that delEntry was
around 1.5% of the total runtime of git-annex whereis. It was being
called once per environment variable per file processed.
Fixed by better caching. Since withIndexFile is almost always run with
the same .git/annex/index file, it can cache the modified environment,
rather than re-modifying it each time called.
(cherry picked from commit 6535aea49a)
This will speed up the common case where a Key is deserialized from
disk, but is then serialized to build eg, the path to the annex object.
Previously attempted in 4536c93bb2
and reverted in 96aba8eff7.
The problems mentioned in the latter commit are addressed now:
Read/Show of KeyData is backwards-compatible with Read/Show of Key from before
this change, so Types.Distribution will keep working.
The Eq instance is fixed.
Also, Key has smart constructors, avoiding needing to remember to update
the cached serialization.
Used git-annex benchmark:
find is 7% faster
whereis is 3% faster
get when all files are already present is 5% faster
Generally, the benchmarks are running 0.1 seconds faster per 2000 files,
on a ram disk in my laptop.
Note from Joey:
git-annex still supports git 2.1, but operates in a degraded fashion.
It would be better for backports of the debian package to also
backport a newer git. This dependency is mostly expressing that,
also that any users who might upgrade git-annex should also upgrade
git.
Also worth noting that the i386ancient autobuilder has git 2.1 on it
(best I have been able to manage there), but luckily the epoch is
bumped to 2, so the dependencies will still be satisfied.
