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authorShawn O. Pearce2011-01-26 22:27:32 +0000
committerShawn O. Pearce2011-01-27 17:38:19 +0000
commitf5fe2dca3cb9f57891e1a4b18832fcc158d0c490 (patch)
tree9270d54a55d19b5d7e32b7b30cf5362711e46cc0 /org.eclipse.jgit.junit
parenta017fdf1124144228dd0395d8a36080212644ed5 (diff)
Teach PackWriter how to reuse an existing object list
Counting the objects needed for packing is the most expensive part of an UploadPack request that has no uninteresting objects (otherwise known as an initial clone). During this phase the PackWriter is enumerating the entire set of objects in this repository, so they can be sent to the client for their new clone. Allow the ObjectReader (and therefore the underlying storage system) to keep a cached list of all reachable objects from a small number of points in the project's history. If one of those points is reached during enumeration of the commit graph, most objects are obtained from the cached list instead of direct traversal. PackWriter uses the list by discarding the current object lists and restarting a traversal from all refs but marking the object list name as uninteresting. This allows PackWriter to enumerate all objects that are more recent than the list creation, or that were on side branches that the list does not include. However, ObjectWalk tags all of the trees and commits within the list commit as UNINTERESTING, which would normally cause PackWriter to construct a thin pack that excludes these objects. To avoid that, addObject() was refactored to allow this list-based enumeration to always include an object, even if it has been tagged UNINTERESTING by the ObjectWalk. This implies the list-based enumeration may only be used for initial clones, where all objects are being sent. The UNINTERESTING labeling occurs because StartGenerator always enables the BoundaryGenerator if the walker is an ObjectWalk and a commit was marked UNINTERESTING, even if RevSort.BOUNDARY was not enabled. This is the default reasonable behavior for an ObjectWalk, but isn't desired here in PackWriter with the list-based enumeration. Rather than trying to change all of this behavior, PackWriter works around it. Because the list name commit's immediate files and trees were all enumerated before the list enumeration itself starts (and are also within the list itself) PackWriter runs the risk of adding the same objects to its ObjectIdSubclassMap twice. Since this breaks the internal map data structure (and also may cause the object to transmit twice), PackWriter needs to use a new "added" RevFlag to track whether or not an object has been put into the outgoing list yet. Change-Id: Ie99ed4d969a6bb20cc2528ac6b8fb91043cee071 Signed-off-by: Shawn O. Pearce <>
Diffstat (limited to 'org.eclipse.jgit.junit')
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