We have debug commands for displaying overall revlog statistics
(debugrevlog) and for dumping a revlog index (debugindex). As part
of investigating various aspects of revlog behavior and performance,
I found it important to have an understanding of how revlog
delta chains behave in practice.
This patch implements a "debugdeltachain" command. For each revision
in a revlog, it dumps information about the delta chain. Which delta
chain it is part of, length of the delta chain, distance since base
revision, info about base revision, size of the delta chain, etc. The
generic formatting facility is used, which means we can templatize
output and get machine readable output like JSON.
This command has already uncovered some weird history in
mozilla-central I didn't know about. So I think it's valuable.
The current heuristic for deciding between storing delta and full texts
is based on ratio of (sizeofdeltas)/(sizeoffulltext).
In some cases (for example a manifest for ahuge repo) this approach
can result in extremely long delta chains (~30,000) which are very slow to
read. (In the case of a manifest ~500ms are added to every hg command because of that).
This commit introduces "revlog.maxchainlength" configuration variable that will
limit delta chain length.
Some versions of python 2.4 write ? instead of <module>. Ignore this detail by
a glob.
This fixes a failure spotted on buildbot, existing since this test lines were
introduced 1a6e234bd7c1.
This is often very handy when hacking/debugging.
Calling util.debugstacktrace('hey') from a place in hg will give something like:
hey at:
./hg:38 in <module>
/home/user/hgsrc/mercurial/dispatch.py:28 in run
/home/user/hgsrc/mercurial/dispatch.py:65 in dispatch
/home/user/hgsrc/mercurial/dispatch.py:88 in _runcatch
/home/user/hgsrc/mercurial/dispatch.py:740 in _dispatch
/home/user/hgsrc/mercurial/dispatch.py:514 in runcommand
/home/user/hgsrc/mercurial/dispatch.py:830 in _runcommand
/home/user/hgsrc/mercurial/dispatch.py:801 in checkargs
/home/user/hgsrc/mercurial/dispatch.py:737 in <lambda>
/home/user/hgsrc/mercurial/util.py:472 in check
...