Bug#912319: find-dbgsym-packages is slow

[Jakub Wilk]

Package: debian-goodies
Version: 0.83
Tags: patch

This patch speeds up find-dbgsym-packages a bit.
Before:

  $ time find-dbgsym-packages /usr/bin/mpv > /dev/null
  
  real    4m44.913s
  user    4m25.116s
  sys     1m20.627s

After:

  $ time find-dbgsym-packages /usr/bin/mpv > /dev/null
  
  real    0m9.182s
  user    0m7.976s
  sys     0m2.415s

--
Jakub Wilk
From 4f732b5e1d544751b9086e54b9e64a39037273a1 Mon Sep 17 00:00:00 2001
From: Jakub Wilk <jw...@jwilk.net>
Date: Tue, 30 Oct 2018 10:23:46 +0100
Subject: [PATCH] find-dbgsym-packages: Reduce number of grep-aptavail calls

The original code called grep-aptavail for each interesting build ID.
This was very slow for binaries using many shared libraries.

Instead, call grep-aptavail once to get all the needed data about
interesting build IDs.
---
 find-dbgsym-packages | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/find-dbgsym-packages b/find-dbgsym-packages
index 9aef361..22b8aca 100755
--- a/find-dbgsym-packages
+++ b/find-dbgsym-packages
@@ -43,12 +43,13 @@ foreach my $arg (@ARGV) {
         %build_ids = get_build_ids_from_file($arg);
     }
 
+    my %debs_from_id = get_debs_from_ids(keys %build_ids);
     foreach my $id (keys %build_ids) {
         my ($path, $name) = @{$build_ids{$id}};
 
         next if $name =~ $vdso_regexp;
 
-        my @p = get_debs_from_id($id);
+        my @p = @{$debs_from_id{$id} // []};
         if (scalar @p == 0) {
             @p = get_debs_from_path($path);
             if (scalar @p == 0) {
@@ -184,15 +185,23 @@ sub get_build_ids_from_pid
     return parse_eu_unstrip($output);
 }
 
-sub get_debs_from_id
+sub get_debs_from_ids
 {
-    my ($id) = @_;
-
+    my $id_regexp = join('|', @_);
+    my %map;
     my $output;
-    $output = capturex([0, 1], qw(grep-aptavail --no-field-names --show-field Package --field Build-IDs --pattern), $id);
-
-    my %pkgs = map { $_ => 1 } split(/\n/, $output);
-    return sort keys %pkgs;
+    $output = capturex([0, 1], qw(grep-aptavail --no-field-names --show-field Package --show-field Build-IDs --field Build-IDs --eregex --pattern), $id_regexp);
+    while ($output =~ /\G(\S+)\n(\S+(?: \S+)*)\n\n/gc) {
+        my $pkg = $1;
+        my $ids = $2;
+        while ($ids =~ m/\b($id_regexp)\b/g) {
+            push @{$map{$1}}, $pkg;
+        }
+    }
+    if (length $output != (pos $output // 0)) {
+        die "Cannot parse grep-aptavail output";
+    }
+    return %map;
 }
 
 sub get_debs_from_path
-- 
2.19.1