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

[Jarno Suni]

** Description changed:

  $ time apt-mark showauto >/dev/null
  
  real	0m0,620s
  user	0m0,557s
  sys	0m0,052s
  
  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
- (name it ./apt-mark-showauto.sh):
+ I could do the job* in fraction of a time using an AWK script
+ (name it ./apt-mark-showauto.awk):
  
- #!/bin/sh
- auto_file='/var/lib/apt/extended_states'
- awk '/^Package:/ {
- 	pkg=$2
- 	while (getline > 0 && $0) {
- 		if ($1 == "Auto-Installed:") {
- 			if ($2==1) print pkg
- 			break
- 		}
+ #!/usr/bin/awk -f
+ BEGIN{
+ 	file="/var/lib/apt/extended_states"
+ 	while ((getline < file) > 0) {
+ 		if ($0 ~ /^Package:/) {
+ 			pkg=$2
+ 			while ((getline < file) > 0 && $0) {
+ 				if ($1 == "Auto-Installed:") {
+ 					if ($2==1) print pkg
+ 					break
+ 				}
+ 			}
+ 		} 
  	}
- }' "$auto_file"
+ }
  
- $ time ./apt-mark-showauto.sh >/dev/null
+ $ time ./apt-mark-showauto.awk >/dev/null
  
- real	0m0,005s
- user	0m0,002s
- sys	0m0,004s
+ real	0m0,004s
+ user	0m0,004s
+ sys	0m0,000s
  
- Tested in Ubuntu 20.04.
+ Tested in Ubuntu 20.04 and mawk 1.3.4 as AWK interpreter.
  
  *) The script omits Architecture information, though. And should apt-
  config be queried for the extended_states file path?
  
  Similarly
  
  apt-cache 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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https://bugs.launchpad.net/bugs/1713219

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

Status in apt package in Ubuntu:
  Triaged

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

  real	0m0,620s
  user	0m0,557s
  sys	0m0,052s

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

  I could do the job* in fraction of a time using an AWK script
  (name it ./apt-mark-showauto.awk):

  #!/usr/bin/awk -f
  BEGIN{
  	file="/var/lib/apt/extended_states"
  	while ((getline < file) > 0) {
  		if ($0 ~ /^Package:/) {
  			pkg=$2
  			while ((getline < file) > 0 && $0) {
  				if ($1 == "Auto-Installed:") {
  					if ($2==1) print pkg
  					break
  				}
  			}
  		} 
  	}
  }

  $ time ./apt-mark-showauto.awk >/dev/null

  real	0m0,004s
  user	0m0,004s
  sys	0m0,000s

  Tested in Ubuntu 20.04 and mawk 1.3.4 as AWK interpreter.

  *) The script omits Architecture information, though. And should apt-
  config be queried for the extended_states file path?

  Similarly

  apt-cache 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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