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changegroup: capture revision delta in a data structure
The current changegroup generation code is tightly coupled to
the revlog API. This tight coupling makes it difficult to implement
alternate storage backends without requiring a large surface area
of the revlog API to be exposed. This is not desirable.
In order to support changegroup generation with non-revlog storage,
we'll need to abstract the concept of delta generation.
This commit is the first step down that road. We introduce a
data structure for representing a delta in a changegroup.
The API still leaves a lot to be desired. But at least we now
have separation between data and actions performed on it.
As part of this, we tweak behavior slightly: we no longer
concatenate the delta prefix with the metadata header. Instead,
we track and emit the prefix as a separate chunk. This shouldn't
have any meaningful impact since all the chunks just get sent to
the wire, the compressor, etc.
Because we're introducing a new object, this does add some
overhead to changegroup execution. `hg perfchangegroupchangelog`
on my clone of the Mercurial repo (~40,000 visible revisions in
the changelog) slows down a bit:
! wall 1.268600 comb 1.270000 user 1.270000 sys 0.000000 (best of 8)
! wall 1.419479 comb 1.410000 user 1.410000 sys 0.000000 (best of 8)
With for `hg bundle -t none-v2 -a /dev/null`:
before: real 6.610 secs (user 6.460+0.000 sys 0.140+0.000)
after: real 7.210 secs (user 7.060+0.000 sys 0.140+0.000)
I plan to claw back this regression in future commits. And I may
even do away with this data structure once the refactor is complete.
For now, it makes things easier to comprehend.
Differential Revision: https://phab.mercurial-scm.org/D4075
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 03 Aug 2018 10:05:26 -0700 |
parents | 1aee2ab0f902 |
children |
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#!/bin/sh # # This is an example of using HGEDITOR to create of diff to review the # changes while committing. # If you want to pass your favourite editor some other parameters # only for Mercurial, modify this: case "${EDITOR}" in "") EDITOR="vi" ;; emacs) EDITOR="$EDITOR -nw" ;; gvim|vim) EDITOR="$EDITOR -f -o" ;; esac HGTMP="" cleanup_exit() { rm -rf "$HGTMP" } # Remove temporary files even if we get interrupted trap "cleanup_exit" 0 # normal exit trap "exit 255" HUP INT QUIT ABRT TERM HGTMP=$(mktemp -d ${TMPDIR-/tmp}/hgeditor.XXXXXX) [ x$HGTMP != x -a -d $HGTMP ] || { echo "Could not create temporary directory! Exiting." 1>&2 exit 1 } ( grep '^HG: changed' "$1" | cut -b 13- | while read changed; do "$HG" diff "$changed" >> "$HGTMP/diff" done ) cat "$1" > "$HGTMP/msg" MD5=$(which md5sum 2>/dev/null) || \ MD5=$(which md5 2>/dev/null) [ -x "${MD5}" ] && CHECKSUM=`${MD5} "$HGTMP/msg"` if [ -s "$HGTMP/diff" ]; then $EDITOR "$HGTMP/msg" "$HGTMP/diff" || exit $? else $EDITOR "$HGTMP/msg" || exit $? fi [ -x "${MD5}" ] && (echo "$CHECKSUM" | ${MD5} -c >/dev/null 2>&1 && exit 13) mv "$HGTMP/msg" "$1" exit $?