more cpan metrics

For a while, I’ve been keeping track of the total usage of my code on the CPAN. It helps me see what people have found useful, and lets me decide how scared to be of introducing back-incompat changes. Sometimes people talk about the sort of catastrophe that can occur if a highly-required module is broken. For example, over 11,000 dists require the code in Getopt-Long. If it broke badly and people installed the new code, it would be a nightmare.

So, I applied my “who needs me?” script to the whole CPAN. It produces a list of every author with dists, showing how many other dists (recursively) use that dist. When an author uses his own dist, it is not counted as a prerequisite. The “total cpan-breaking power” score is more accurate that way.

This scoreboard is quite different to Simon Wistow’s CPAN Leaderboard. Here’s a comparison:

author volume requiredness
ZOFFIX 1 145
ADAMK 2 32
RJBS 3 43
GBARR 114 1
PMQS 221 2
SAPER 32 5

[Edit: I’ve had to clarify this to a few people, so here is a bit of explanation. The above numbers are ranks of the analyzed data. In other words, GBARR is 114th most prolific (well, he is tied in the 114th rank) but is the author with the most relied-upon code. They are not scores. Each dist is counted, so if you uploaded 100,000 dists, none of which were required by anything, your requiredness rank would still become 1. This may change.]

The program is included below. It’s a quick and dirty hack, but it was fun to write and look at.

use strict;
use warnings;
use 5.010;
use DBI;
use JSON::XS;

my $dbh = DBI->connect('dbi:SQLite:dbname=cpants_all.db', undef, undef);

my $authors = $dbh->selectall_arrayref(
  "SELECT id, pauseid
  FROM author
  ORDER BY pauseid"

my @results;

for my $author (@$authors) {
  my ($author_id, $pauseid) = @$author;

  my $dists = $dbh->selectall_arrayref(
    "SELECT id, dist FROM dist WHERE author = ? ORDER BY dist",

  my %analysis;

  analyze_dist(\%analysis, $author_id, $_) for @$dists;

  my $sum = 0;
  $sum += $_ for values %analysis;

  next unless $sum;

  warn "$pauseid,$sum\n";
  push @results, {
    pauseid => $pauseid,
    result  => $sum,
    dists   => \%analysis,

my $JSON = JSON::XS->new;
for my $author (sort { $b->{result} <=> $a->{result} } @results) {
  say $JSON->encode($author);

sub analyze_dist {
  my ($analysis, $author_id, $dist, $seen, $add_to) = @_;
  $seen ||= {};
  $add_to ||= $dist->[1];

  my @queue = $dist;

  $analysis->{ $add_to }++;

  my $needed_by = $dbh->selectall_arrayref(
    "SELECT p.dist, d.dist AS name
    FROM prereq p
    JOIN dist d ON = p.dist
    WHERE p.in_dist = ?
    AND author <> ?",

  for my $needed (@$needed_by) {
    next if $seen->{ $needed->[1] };
    $seen->{ $dist->[1] }++;
    analyze_dist($analysis, $author_id, $needed, $seen, $add_to);

You can find the results of the results as of last night in my drop box.

Written on November 4, 2008
cpan   perl   programming