On Tue, Jan 19, 2021 at 03:42:51PM +0100, Jacob Vosmaer wrote: > The previous implementation of ls-refs would perform exactly one ref > walk, matching each ref against the prefixes (if any) provided by the > user. This can be expensive if there are a lot of refs and the user > only cares about a small subset of them. > > In this patch we analyze the prefixes provided by the user and build a > minimal set of disjoint prefixes that contains all of them. We then do > a ref walk for each of these minimal prefixes. Thanks for posting this. I have a vague recollection that we considered this either when we did the for-each-ref prefixes, or when we added ls-refs prefixes, but I can't seem to find either. At any rate, at GitHub we haven't generally found it to be a problem because our horrifically-large repos tend to be aggregated alternates repos, not the ones people serve upload-pack out of (though I did just time it, and some of our largest repos should save a few hundred milliseconds per advertisement, which is certainly not nothing). I do think we should reuse the code from ref-filter, as Taylor showed. > This commit also fixes a bug in ls-refs.c that was not triggered > before: we were using a strvec set to zero, which is not how you are > supposed to initialize a strvec. We now call strvec_init after zeroing. Good catch. It didn't matter until now because nobody relied on having a NULL entry when no prefix had been added (instead, they always iterated over prefixes->nr). IMHO that is worth fixing as a separate commit. -Peff
