git/t/t4042-diff-textconv-caching.sh
Jeff King d9bae1a178 diff: cache textconv output
Running a textconv filter can take a long time. It's
particularly bad for a large file which needs to be spooled
to disk, but even for small files, the fork+exec overhead
can add up for something like "git log -p".

This patch uses the notes-cache mechanism to keep a fast
cache of textconv output. Caches are stored in
refs/notes/textconv/$x, where $x is the userdiff driver
defined in gitattributes.

Caching is enabled only if diff.$x.cachetextconv is true.

In my test repo, on a commit with 45 jpg and avi files
changed and a textconv to show their exif tags:

  [before]
  $ time git show >/dev/null
  real    0m13.724s
  user    0m12.057s
  sys     0m1.624s

  [after, first run]
  $ git config diff.mfo.cachetextconv true
  $ time git show >/dev/null
  real    0m14.252s
  user    0m12.197s
  sys     0m1.800s

  [after, subsequent runs]
  $ time git show >/dev/null
  real    0m0.352s
  user    0m0.148s
  sys     0m0.200s

So for a slight (3.8%) cost on the first run, we achieve an
almost 40x speed up on subsequent runs.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-04-02 00:05:31 -07:00

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#!/bin/sh
test_description='test textconv caching'
. ./test-lib.sh
cat >helper <<'EOF'
#!/bin/sh
sed 's/^/converted: /' "$@" >helper.out
cat helper.out
EOF
chmod +x helper
test_expect_success 'setup' '
echo foo content 1 >foo.bin &&
echo bar content 1 >bar.bin &&
git add . &&
git commit -m one &&
echo foo content 2 >foo.bin &&
echo bar content 2 >bar.bin &&
git commit -a -m two &&
echo "*.bin diff=magic" >.gitattributes &&
git config diff.magic.textconv ./helper &&
git config diff.magic.cachetextconv true
'
cat >expect <<EOF
diff --git a/bar.bin b/bar.bin
index fcf9166..28283d5 100644
--- a/bar.bin
+++ b/bar.bin
@@ -1 +1 @@
-converted: bar content 1
+converted: bar content 2
diff --git a/foo.bin b/foo.bin
index d5b9fe3..1345db2 100644
--- a/foo.bin
+++ b/foo.bin
@@ -1 +1 @@
-converted: foo content 1
+converted: foo content 2
EOF
test_expect_success 'first textconv works' '
git diff HEAD^ HEAD >actual &&
test_cmp expect actual
'
test_expect_success 'cached textconv produces same output' '
git diff HEAD^ HEAD >actual &&
test_cmp expect actual
'
test_expect_success 'cached textconv does not run helper' '
rm -f helper.out &&
git diff HEAD^ HEAD >actual &&
test_cmp expect actual &&
! test -r helper.out
'
cat >expect <<EOF
diff --git a/bar.bin b/bar.bin
index fcf9166..28283d5 100644
--- a/bar.bin
+++ b/bar.bin
@@ -1,2 +1,2 @@
converted: other
-converted: bar content 1
+converted: bar content 2
diff --git a/foo.bin b/foo.bin
index d5b9fe3..1345db2 100644
--- a/foo.bin
+++ b/foo.bin
@@ -1,2 +1,2 @@
converted: other
-converted: foo content 1
+converted: foo content 2
EOF
test_expect_success 'changing textconv invalidates cache' '
echo other >other &&
git config diff.magic.textconv "./helper other" &&
git diff HEAD^ HEAD >actual &&
test_cmp expect actual
'
cat >expect <<EOF
diff --git a/bar.bin b/bar.bin
index fcf9166..28283d5 100644
--- a/bar.bin
+++ b/bar.bin
@@ -1,2 +1,2 @@
converted: other
-converted: bar content 1
+converted: bar content 2
diff --git a/foo.bin b/foo.bin
index d5b9fe3..1345db2 100644
--- a/foo.bin
+++ b/foo.bin
@@ -1 +1 @@
-converted: foo content 1
+converted: foo content 2
EOF
test_expect_success 'switching diff driver produces correct results' '
git config diff.moremagic.textconv ./helper &&
echo foo.bin diff=moremagic >>.gitattributes &&
git diff HEAD^ HEAD >actual &&
test_cmp expect actual
'
test_done