keep track of unresolved value of symbolic-ref in iterator #1712
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Since ref iterators do not hold onto the direct value of a reference without resolving it, the only way to get ahold of a direct value of a symbolic ref is to make a separate call to refs_read_symbolic_ref. To make accessing the direct value of a symbolic ref more efficient, let's save the direct value of the ref in the cache so the iterator has access to it. To do so, we need to add an argument to refs_resolve_ref_unsafe to save the direct value of the reference to. Signed-off-by: John Cai <johncai86@gmail.com>
There is no way for callers of the refs api functions that use iterators to get a hold of a direct value of a symbolic ref before its resolved in the callback functions, as either each_ref_fn nor each_repo_ref_fn have an argument for this. The previous commit started to save the value of the direct reference in the iterator. Add an argument to each_repo_ref_fn that gets called with the direct value of a refernce, and pass the value through from the iterator. Signed-off-by: John Cai <johncai86@gmail.com>
A past commit allows ref iterators to keep the value of a symref. The previous commit exposed this value through a parameter added to each_repo_ref_fn for callers to have access to it. Add the same parameter to each_ref_fn so that callers to the ref APIs that use this function as a callback also can have acess to the unresolved value of a symbolic ref. Signed-off-by: John Cai <johncai86@gmail.com>
With a previous commit, the reference the symbolic ref points is saved in the ref iterator records. Instead of making a separate call to resolve_refdup() each time, we can just populate the ref_array_item with the value from the iterator. Signed-off-by: John Cai <johncai86@gmail.com>
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For reftable development, it's useful to be able to print out the direct value of a symbolic reference before resolution. This is currently possible with git-for-each-ref, but since the iterators do not keep track of the value of the symbolic ref, a separate call needs to be made each time.
Address this inefficiency by keeping track of the value of the symbolic reference in the ref iterator. This patch series also ends with a commit to use this value in the iterator through callbacks in ref-filter.c.
This series started with [1] but I decided to send a separate patch series since it is substantially different.
Benchmarking shows that with these changes, we experience a significant speedup in git-for-each-ref(1) when %(symref) is used in the format string:
$ hyperfine --warmup 5 "git for-each-ref --format='%(refname) %(objectname) %(symref)'" "~/Projects/git/git for-each-ref --format='%(refname) %(objectname) %(symref)'"
Benchmark 1: git for-each-ref --format='%(refname) %(objectname) %(symref)'
Time (mean ± σ): 210.0 ms ± 9.1 ms [User: 5.8 ms, System: 11.8 ms]
Range (min … max): 203.4 ms … 228.8 ms 12 runs
Benchmark 2: ~/Projects/git/git for-each-ref --format='%(refname) %(objectname) %(symref)'
Time (mean ± σ): 7.4 ms ± 0.7 ms [User: 2.6 ms, System: 3.9 ms]
Range (min … max): 5.9 ms … 11.7 ms 273 runs
Summary
~/Projects/git/git for-each-ref --format='%(refname) %(objectname) %(symref)' ran
28.47 ± 2.86 times faster than git for-each-ref --format='%(refname) %(objectname) %(symref)'
cc: Phillip Wood phillip.wood123@gmail.com
cc: "Kristoffer Haugsbakk" code@khaugsbakk.name
cc: Jeff King peff@peff.net
cc: Patrick Steinhardt ps@pks.im
cc: Jean-Noël Avila avila.jn@gmail.com