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| author | David Kalnischkies <david@kalnischkies.de> | 2016-01-07 20:32:09 +0100 |
|---|---|---|
| committer | David Kalnischkies <david@kalnischkies.de> | 2016-01-08 15:40:01 +0100 |
| commit | 0179cfa83cf0042235eda41db7f35c420781c63e (patch) | |
| tree | a1b49bb2d40ae34a5d06139e7ecd203ba0733c8f /doc | |
| parent | 912a61312a0463b46d6560756c89146f59daaab6 (diff) | |
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.
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/acquire-additional-files.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/doc/acquire-additional-files.txt b/doc/acquire-additional-files.txt index 32b0e4470..68af9a5b0 100644 --- a/doc/acquire-additional-files.txt +++ b/doc/acquire-additional-files.txt @@ -124,6 +124,10 @@ aren't accidentally used by front-ends: type a front-end can't open transparently. This should always be a temporary workaround through and a bug should be reported against the front-end in question. +* KeepCompressedAs: The default value is a space separated list of + compression types supported by apt (see previous option) which is + sorted by the cost-value of the compression in ascending order, + except that cost=0 "compressions" (like uncompressed) are listed last. # More examples |