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t3305: check notes fanout more carefully and robustly

Browse source 
In short, before this patch, this test script:
 - creates many notes
 - verifies that all notes in the notes tree has a fanout of 1
 - removes most notes
 - verifies that the notes in the notes tree now has a fanout of 0

The fanout verification only happened twice: after creating all the
notes, and after removing most of them.

This patch strengthens the test by checking the fanout after _each_
added/removed note: We assert that the switch from fanout 0 -> 1
happens exactly once while adding notes (and that the switch pervades
the entire notes tree). Likewise, we assert that the switch from
fanout 1 -> 0 happens exactly once while removing notes.

Additionally, we decrease the number of notes left after removal,
from 50 to 15 notes, in order to ensure that fanout 1 -> 0 transition
keeps happening regardless of external factors[1].

[1]: Currently (with the SHA1 hash function and the deterministic
object ids of the test environment) the fanout heuristic in the notes
code happens to switch from 0 -> 1 at 109 notes, and from 1 -> 0 at
59 notes. However, changing the hash function or other external
factors will vary these numbers, and the latter may - in theory - go
as low as 15. For more details, please see the discussion at
https://public-inbox.org/git/20200125230035.136348-4-sandals@crustytoothpaste.net/

Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Brian M. Carlson <sandals@crustytoothpaste.net>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johan Herland 2020-02-03 22:04:44 +01:00 committed by Junio C Hamano
parent b6d4d82bd5
commit e1c5253951
1 changed files with 76 additions and 25 deletions
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101
t/t3305-notes-fanout.sh
View file

@ -4,6 +4,32 @@ test_description='Test that adding/removing many notes triggers automatic fanout
. ./test-lib.sh
path_has_fanout() {
path=$1 &&
fanout=$2 &&
after_last_slash=$((40 - $fanout * 2)) &&
echo $path | grep -q "^\([0-9a-f]\{2\}/\)\{$fanout\}[0-9a-f]\{$after_last_slash\}$"
}
touched_one_note_with_fanout() {
notes_commit=$1 &&
modification=$2 && # 'A' for addition, 'D' for deletion
fanout=$3 &&
diff=$(git diff-tree --no-commit-id --name-status --root -r $notes_commit) &&
path=$(echo $diff | sed -e "s/^$modification[\t ]//") &&
path_has_fanout "$path" $fanout;
}
all_notes_have_fanout() {
notes_commit=$1 &&
fanout=$2 &&
git ls-tree -r --name-only $notes_commit 2>/dev/null |
while read path
do
path_has_fanout $path $fanout || return 1
done
}
test_expect_success 'creating many notes with git-notes' '
num_notes=300 &&
i=0 &&
@ -20,7 +46,7 @@ test_expect_success 'creating many notes with git-notes' '
test_expect_success 'many notes created correctly with git-notes' '
git log | grep "^ " > output &&
i=300 &&
i=$num_notes &&
while test $i -gt 0
do
echo " commit #$i" &&
@ -30,34 +56,46 @@ test_expect_success 'many notes created correctly with git-notes' '
test_cmp expect output
'
test_expect_success 'many notes created with git-notes triggers fanout' '
# Expect entire notes tree to have a fanout == 1
git ls-tree -r --name-only refs/notes/commits |
while read path
test_expect_success 'stable fanout 0 is followed by stable fanout 1' '
i=$num_notes &&
fanout=0 &&
while test $i -gt 0
do
echo $path | grep "^../[0-9a-f]*$" || {
echo "Invalid path \"$path\"" &&
return 1;
}
done
i=$(($i - 1)) &&
if touched_one_note_with_fanout refs/notes/commits~$i A $fanout
then
continue
elif test $fanout -eq 0
then
fanout=1 &&
if all_notes_have_fanout refs/notes/commits~$i $fanout
then
echo "Fanout 0 -> 1 at refs/notes/commits~$i" &&
continue
fi
fi &&
echo "Failed fanout=$fanout check at refs/notes/commits~$i" &&
git ls-tree -r --name-only refs/notes/commits~$i &&
return 1
done &&
all_notes_have_fanout refs/notes/commits 1
'
test_expect_success 'deleting most notes with git-notes' '
num_notes=250 &&
remove_notes=285 &&
i=0 &&
git rev-list HEAD |
while test $i -lt $num_notes && read sha1
while test $i -lt $remove_notes && read sha1
do
i=$(($i + 1)) &&
test_tick &&
git notes remove "$sha1" ||
exit 1
git notes remove "$sha1" 2>/dev/null || return 1
done
'
test_expect_success 'most notes deleted correctly with git-notes' '
git log HEAD~250 | grep "^ " > output &&
i=50 &&
git log HEAD~$remove_notes | grep "^ " > output &&
i=$(($num_notes - $remove_notes)) &&
while test $i -gt 0
do
echo " commit #$i" &&
@ -67,16 +105,29 @@ test_expect_success 'most notes deleted correctly with git-notes' '
test_cmp expect output
'
test_expect_success 'deleting most notes triggers fanout consolidation' '
# Expect entire notes tree to have a fanout == 0
git ls-tree -r --name-only refs/notes/commits |
while read path
test_expect_success 'stable fanout 1 is followed by stable fanout 0' '
i=$remove_notes &&
fanout=1 &&
while test $i -gt 0
do
echo $path | grep -v "^../.*" || {
echo "Invalid path \"$path\"" &&
return 1;
}
done
i=$(($i - 1)) &&
if touched_one_note_with_fanout refs/notes/commits~$i D $fanout
then
continue
elif test $fanout -eq 1
then
fanout=0 &&
if all_notes_have_fanout refs/notes/commits~$i $fanout
then
echo "Fanout 1 -> 0 at refs/notes/commits~$i" &&
continue
fi
fi &&
echo "Failed fanout=$fanout check at refs/notes/commits~$i" &&
git ls-tree -r --name-only refs/notes/commits~$i &&
return 1
done &&
all_notes_have_fanout refs/notes/commits 0
'
test_done