keep compressed indexes in a low-cost format

Downloading and storing are two different operations were different
compression types can be preferred. For downloading we provide the
choice via Acquire::CompressionTypes::Order as there is a choice to
be made between download size and speed – and limited by whats available
in the repository.

Storage on the other hand has all compressions currently supported by
apt available and to reduce runtime of tools accessing these files the
compression type should be a low-cost format in terms of decompression.

apt traditionally stores its indexes uncompressed on disk, but has
options to keep them compressed. Now that apt downloads additional files
we also deal with files which simply can't be stored uncompressed as
they are just too big (like Contents for apt-file). Traditionally they
are downloaded in a low-cost format (gz) as repositories do not provide
other formats, but there might be even lower-cost formats and for
download we could introduce higher-cost in the repositories.

Downloading an entire index potentially requires recompression to
another format, so an update takes potentially longer – but big files
are usually updated via pdiffs which has to de- and re-compress anyhow
and does it on the fly anyhow, so there is no extra time needed and in
general it seems to be benefitial to invest the time in update to save
time later on file access.

1 files changed, 7 insertions, 3 deletions

diff --git a/test/integration/test-apt-update-unauth b/test/integration/test-apt-update-unauth
index 2ececc4f6..ef1e4eca7 100755
--- a/test/integration/test-apt-update-unauth
+++ b/test/integration/test-apt-update-unauth
@@ -12,6 +12,7 @@ umask 022
 
 setupenvironment
 configarchitecture "i386"
+configcompression '.' 'xz'
 
 insertpackage 'unstable' 'foo' 'i386' '1.0'
 insertsource 'unstable' 'foo' 'any' '1.0'
@@ -45,7 +46,7 @@ runtest() {
     listcurrentlistsdirectory > lists.before
 
     # update and ensure all is reverted on the hashsum failure
-    testfailure aptget update -o Debug::Acquire::Transaction=0 -o Debug::pkgAcquire::Auth=1 -o Debug::pkgAcquire::worker=0 -o Debug::acquire::http=0
+    testfailure aptget update -o Debug::Acquire::Transaction=1 -o Debug::pkgAcquire::Auth=1 -o Debug::pkgAcquire::worker=0 -o Debug::acquire::http=0
 
     # ensure we have before what we have after
     msgtest 'Check rollback on going from' 'unauth -> auth'
@@ -53,10 +54,13 @@ runtest() {
     if cmp lists.before lists.after; then
         msgpass
     else
+	echo >&2
 	echo >&2 '### Output of previous apt-get update ###'
-	cat >&2 rootdir/tmp/testfailure.output
+	cat >&2 rootdir/tmp/testfailure.output || true
 	echo >&2 '### Changes in the lists-directory: ###'
-	diff -u >&2 lists.before lists.after
+	diff -u >&2 lists.before lists.after || true
+	echo >&2 '### Contents of the lists-directory: ###'
+	ls -l rootdir/var/lib/apt/lists rootdir/var/lib/apt/lists/partial || true
 	msgfail
     fi