On 3/6/2023 7:28 PM, Taylor Blau wrote: > On Mon, Mar 06, 2023 at 02:54:00PM -0800, Junio C Hamano wrote: >> "Derrick Stolee via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes: >> >>> @@ -1008,6 +1008,7 @@ void reprepare_packed_git(struct repository *r) >>> struct object_directory *odb; >>> >>> obj_read_lock(); >>> + reprepare_alt_odb(r); >>> for (odb = r->objects->odb; odb; odb = odb->next) >>> odb_clear_loose_cache(odb); >> >> Hmph, if there was an old alternate ODB from which we took some >> loose object from and cached, and if that ODB no longer is on the >> updated alternate list, would we now fail to clear the loose objects >> cache for the ODB? Or are we only prepared for seeing "more" >> alternates and assume no existing alternates go away? > > Based on my understanding of the patch, we are only prepared to see > "more" alternates, rather than some existing alternate going away. > > That being said, I am not certain that is how it works. Perhaps an > alternate "goes away", but does not actually get removed from the list > of alternate ODBs. If that's the case, any object lookup in that > now-missing ODB would fail, but any subsequent ODBs which were added > after calling reprepare_alt_odb() would succeed on that object lookup. > > So, I don't know. I don't have the implementation details of the > alternates ODB mechanism paged in enough to say for sure. Hopefully > Stolee can point us in the right direction. The prepare_alt_odb() call only _adds_ to the linked odb list. It will not remove any existing ODBs. Adding this reprepare_*() method makes it such that we can use the union of the alternates available across the lifetime of the process. Thanks, -Stolee
