I've been doing a bit of research here and have found a number of nodes with some helpful information, but none I believe represents quite what I'm trying to accomplish.

I have two similar large files 1GB+ in size. I need to compare file1 to file2 with common keys to find differences in the values of file1 to file2. My initial thought was to load both into separate hashes and iterate hash1 over hash2. However, with files of this size I cannot store in memory. I've read of a few modules that may be of help and a lot of suggestion of using a RDBMS. Looking for some help and direction. Thanks! 
sub process {
   open (TODAY_IN, $out);
   foreach my $line_t (<TODAY_IN>){
      ($path, $type, $size, $link, $nfiles) = split(/\s+/, $line_t);
      $today{$path}{'Type'} = $type;
      $today{$path}{'Size'} = $size;
      $today{$path}{'Link'} = $link;
      $today{$path}{'NFILES'} = $nfiles;
   }
   close TODAY_IN;
   open (YESTERDAY_IN, $comp);
   foreach my $line_y (<YESTERDAY_IN>){
      ($path, $type, $size, $link, $nfiles) = split(/\s+/, $line_y);
      $yesterday{$path}{'Type'} = $type;
      $yesterday{$path}{'Size'} = $size;
      $yesterday{$path}{'Link'} = $link;
      $yesterday{$path}{'NFILES'} = $nfiles;
   }
   close YESTERDAY_IN;
   diff(%today, %yesterday);
}

sub diff {
   open (COMP, ">$final");
   foreach $key (keys %today){
      if (exists $yesterday{$key}){
         $size_t = $today{$key}{'Size'};
         $size_y = $yesterday{$key}{'Size'};
         $nfiles_t = $today{$key}{'NFILES'};
         $nfiles_y = $yesterday{$key}{'NFILES'};
         if ($size_y > 0 && $size_t > 0){
            if ($size_t > $size_y){
               my $diff_t = (1-($size_y/$size_t))*100;
               if ($diff_t >= $max_size_diff){
                  $diffOut{$key}{'SizeYest'} = $size_y;
                  $diffOut{$key}{'SizeToday'}  = $size_t;
                  $diffOut{$key}{'SizeDiff'} = $diff_t;
                  print COMP "$key\tYEST:$diffOut{$key}{'SizeYest'}\tT
+OD:$diffOut{$key}{'SizeToday'}\tDIFF:$diffOut{$key}{'SizeDiff'}\n";
               }
            }
            elsif ($size_y > $size_t){
               my $diff_y = (1-($size_t/$size_y))*100;
               if ($diff_y >= $max_size_diff){
                  $diffOut{$key}{'SizeToday'}  = $size_t;
                  $diffOut{$key}{'SizeYest'} = $size_y;
                  $diffOut{$key}{'SizeDiff'} = $diff_y;
                  print COMP "$key\tYEST:$diffOut{$key}{'SizeYest'}\tT
+OD:$diffOut{$key}{'SizeToday'}\tDIFF:$diffOut{$key}{'SizeDiff'}\n";
               }
            }
            if (-d $key){
               if ($nfiles_y > 0 && $nfiles_t > 0){
                  $diffFiles = $nfiles_t-$nfiles_y;
                  if ($diffFiles > $max_file_diff){
                     $diffOut{$key}{'FileDiff'} = $diffFiles;
                     print COMP "$key\tFDIFF:$diffOut{$key}{'FileDiff'
+}\n";
                  }
               }
            }
         }
      }
      else {
         $diffOut{$key}{'SizeToday'} = $size_t;
         $diffOut{$key}{'SizeYest'} = 0;
         $diffOut{$key}{'SizeDiff'} = "New";
         print COMP "$key\tYEST:$diffOut{$key}{'SizeYest'}\tTOD:$diffO
+ut{$key}{'SizeToday'}\tDIFF:$diffOut{$key}{'SizeDiff'}\n";
      }
   }
   close COMP;
}

[download]

In reply to Compare large files by boardryder

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.