view tests/test-cat @ 2079:ee96ca273f32

New lazy index code for revlogs.

This tunes for large repositories.   It does not read the whole
index file in one big chunk, but tries to buffer reads in more
reasonable chunks instead.

Search speeds are improved in two ways.  When trying to find a
specific sha hash, it searches from the end of the file backward.
More recent entries are more likely to be relevant, especially the
tip.

Also, this can load only the mapping of nodes to revlog index number.
Loading the map uses less cpu (no struct.unpack) and much less
memory than loading both the map and the index.

This cuts down the time for hg tip on the 80,000 changeset
kernel repo from 1.8s to 3.69s.  Most commands the pull a single
rev out of a big index get roughly the same benefit.  Commands
that read the whole index are not slower.

#!/bin/sh
#
mkdir t
cd t
hg init
echo 0 > a
echo 0 > b
hg ci -A -m m -d "1000000 0"
hg rm a
hg cat a
sleep 1 # make sure mtime is changed
echo 1 > b
hg ci -m m -d "1000000 0"
echo 2 > b
hg cat -r 0 a
hg cat -r 0 b
hg cat -r 1 a
hg cat -r 1 b