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, 2 insertions, 9 deletions

diff --git a/apt-pkg/acquire-item.h b/apt-pkg/acquire-item.h
index 93ff0a9c3..306b1772a 100644
--- a/apt-pkg/acquire-item.h
+++ b/apt-pkg/acquire-item.h
@@ -914,16 +914,12 @@ class APT_HIDDEN pkgAcqIndex : public pkgAcqBaseIndex
    AllStages Stage;
 
    /** \brief Handle what needs to be done when the download is done */
-   void StageDownloadDone(std::string const &Message,
-                          HashStringList const &Hashes,
-                          pkgAcquire::MethodConfig const * const Cfg);
+   void StageDownloadDone(std::string const &Message);
 
    /** \brief Handle what needs to be done when the decompression/copy is
     *         done 
     */
-   void StageDecompressDone(std::string const &Message,
-                            HashStringList const &Hashes,
-                            pkgAcquire::MethodConfig const * const Cfg);
+   void StageDecompressDone();
 
    /** \brief If \b set, this partially downloaded file will be
     *  removed when the download completes.
@@ -941,9 +937,6 @@ class APT_HIDDEN pkgAcqIndex : public pkgAcqBaseIndex
    /** \brief Do the changes needed to fetch via AptByHash (if needed) */
    void InitByHashIfNeeded();
 
-   /** \brief Schedule file for verification after a IMS hit */
-   void ReverifyAfterIMS();
-
    /** \brief Get the full pathname of the final file for the current URI */
    virtual std::string GetFinalFilename() const APT_OVERRIDE;