64615b44e6
The reverse index for a pack is used to quickly find an object's position in the pack's forward index based on that object's pack offset. It is currently computed from the forward index by sorting the index entries by the corresponding pack offset. This computation uses bucket sort with insertion sort, which has an average runtime of O(n log n) and worst case runtime of O(n^2); and memory usage of 3*size(int)*n because it maintains 3 int arrays, even after sorting is completed. The computation must be performed every time that the reverse index object is created in memory. In contrast, Cgit persists a pack reverse index file to avoid recomputing the reverse index ordering every time that it is needed. Instead they write a file with format https://git-scm.com/docs/pack-format#_pack_rev_files_have_the_format which can later be read and parsed into an in-memory reverse index each time it is needed. Introduce these reverse index files to JGit. PackReverseIndexWriter writes out a reverse index file to be read later when needed. Subclass PackReverseIndexWriterV1 writes a file with the official version 1 format. To avoid temporarily allocating an Integer collection while sorting and writing out the contents, using memory 4*size(Integer)*n, use an IntList and its #sort method, which uses quicksort. Change-Id: I6437745777a16f723e2f1cfcce4e0d94e599dcee Signed-off-by: Anna Papitto <annapapitto@google.com> |
||
|---|---|---|
| .. | ||
| .settings | ||
| META-INF | ||
| findBugs | ||
| resources/org/eclipse/jgit | ||
| src/org/eclipse/jgit | ||
| .classpath | ||
| .fbprefs | ||
| .gitignore | ||
| .project | ||
| BUILD | ||
| about.html | ||
| build.properties | ||
| plugin.properties | ||
| pom.xml | ||