Webmaster Forum / Perl / Modules / December 2006

Hi all,  topical question here regarding Sort::Maker

I have a poorly designed db table over which I have no control.  The
data isn't normalized but for each row I'd like to return the column
numbers which have the highest number of counts, and the highest column
number with any counts at all.  I refer to these values as mode and max
respectively, but please refer to my code and it's output below for a
better understanding.  (I have provided sample input data and mimicked
the fetchrow_hashref function provided by DBI)

Both sorts seem klunky, and after the discussion about the efficiency
gains given by Sort::Maker in another thread I'd like to take advantage
if I can (the sorts must be performed for each row returned by the
database).

I'm not sure how to pass in the information in the $hashref to
make_sorter.  Advice would be greatly appreciated.

TIA,
-jp

Code:
 #!/usr/bin/perl

 use strict;
 use warnings;

 print "id\tmode\tmax\n";
 while ( my $hashref = fetchrow_hashref() ) {
     my $id   = $hashref->{id};

     # mode = col number with greatest count
     my $mode = ( map  { $_->[0] }
                 sort { $b->[1] <=> $a->[1] }
                 map  { [ $_, $hashref->{"col$_"} ] } 1..5 )[0];

     # max = highest col number with any count
     my $max  = ( sort { $b <=> $a }
                 map  { $_ if $hashref->{"col$_"} > 0 } 1..5 )[0];

     $max = 1 if $max eq '';   #all zeros

     print "$id\t$mode\t$max\n";
 }

 { my @columns;

   sub fetchrow_hashref {

     # silence warning that $line may be equal to 0 below
     no warnings 'misc';
     my $line = <DATA> or return;

     if ( $. == 1 ) {
         @columns = split ' ', substr $line, 1;
         return fetchrow_hashref();
     }

     my %hash;
     @hash{ @columns } = split ' ', $line;

     return \%hash;
 } }

 __DATA__
 #id     col1    col2    col3    col4    col5
 1       2       8       8       0       0
 2       5       0       0       0       0
 3       3       2       8       2       5
 4       4       3       8       2       0
 5       5       7       7       0       0
 6       9       5       6       0       0
 7       6       4       5       7       0
 8       2       3       0       0       0
 9       9       2       3       3       5
 10      0       4       1       0       0
 11      0       0       0       0       0
 12      1       1       1       1       1

Output:
 id      mode    max
 1       2       3
 2       1       1
 3       3       5
 4       3       4
 5       2       3
 6       1       3
 7       4       4
 8       2       2
 9       1       5
 10      2       3
 11      1       1
 12      1       5