[Bug 1713219] Re: 'apt-mark showauto' and 'apt show' is slow

[David Kalnischkies]

Mechanical train signals used to signal if the next section is clear vs.
blocked by another train used to have the arm raised if it was clear and
down if not. That was so that if the mechanic would fail in some way the
arm would fall down and rest in the "blocked" state rather than in a
"clear" state potentially causing huge problems.

I like to think that it is the same here. If the data gets lost,
corrupted or whatever we fall back to a safe state: protected from
autoremove as manual installed rather than causing havoc. In reality the
original implementer might not have thought that far, but he isn't
around anymore to ask him… and it isn't really important, is it?

Your precived "slowness" might be an out of dated cache. Have you
recently run an apt command with root rights? If it is not run as root
apt will build the cache in memory only. That cache can also easily be
many megabytes big, which can take a while to shuffle into disk cache on
a slow spinning disk.

Your script might be very fast, but it is also wrong (Auto-Installed is
not the only field which can be set there even if for apt its the only
one used. Other clients could use other fields and in that case apt
would of course also keep the manual entries…) and doesn't even begin to
support what apt-mark does. If you want to constructively work on
speeding apt in these cases is to look at where the time is lost and
optimize those codepaths. Showing off your script-foo is not helping and
borderline trolling… after all, I can easily point at a lot of traveling
salesperson (well, perhaps not in corona times), but that seems like a
very hard problem for computers somehow.

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https://bugs.launchpad.net/bugs/1713219

Title:
  'apt-mark showauto' and 'apt show' is slow

Status in apt package in Ubuntu:
  Triaged

Bug description:
  $ time apt-mark showauto >/dev/null

  real	0m0.587s
  user	0m0.552s
  sys	0m0.016s

  When I run the command first time, it is even much slower.

  I could do the job in fraction of a time using awk in POSIX shell
  script:

  auto_file='/var/lib/apt/extended_states'
  eval $(apt-config shell auto_file Dir::State::extended_states/f)
  awk '/^Package:/ {
  	pkg=$2
  	getline; arch=$2
  	getline
  	if($2==1) print pkg ":" arch
  }' "$auto_file" | CL_ALL=C sort -u

  real	0m0.019s
  user	0m0.008s
  sys	0m0.000s

  That prints architecture for every package and shows entries in
  slightly different order, though. And the file could be out of date
  showing packages that are not installed?!?

  Similarly

  apt show <pkg>

  is slow. (It also shows whether a package is manually or automatically
  installed.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: apt 1.0.1ubuntu2.17
  ProcVersionSignature: Ubuntu 4.4.0-92.115~14.04.1-generic 4.4.76
  Uname: Linux 4.4.0-92-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.25
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Sat Aug 26 12:59:00 2017
  EcryptfsInUse: Yes
  InstallationDate: Installed on 2014-09-21 (1070 days ago)
  InstallationMedia: Ubuntu-Studio 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.1)
  SourcePackage: apt
  UpgradeStatus: No upgrade log present (probably fresh install)
  modified.conffile..etc.cron.daily.apt: [modified]
  modified.conffile..etc.kernel.postinst.d.apt.auto.removal: [modified]
  mtime.conffile..etc.cron.daily.apt: 2017-05-03T10:27:27.617839
  mtime.conffile..etc.kernel.postinst.d.apt.auto.removal: 2017-06-01T14:39:39.236080

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