The general idea of "cosequential processing" is that the files are sorted on the key or keys you are matching on. That way you only need to keep one in memory for each file at a time, although you may have to rewind if you are doing a many-to-many join. More details of what you are doing now would be helpful.

One method that might be useful (hard to tell from your description) is to merge all of the files into one (using sort on Unix or sort -m if they are already sorted). Then all the keys that match will be together in the file and it is simple to write a program to process them. You may need to pre-process the files to make them suitable for this method.

Updated:Yes, now that I see your data, it looks like this method would be appropriate. You can sort -t, -k 1n,2 -k 4,5 file1 file2 file3 ... > sorted. Then it's a simple matter to process the sorted file:

#!perl -w
use strict;
my @sum = ();
my $prevkey ="";
while (<>) {
  chomp;
  my @data = split /,/, $_;
  next if $data[0] == 1; # skip headers

  my $key = join(",", @data[0, 1, 3, 4]);
  if ($key eq $prevkey) {
    for (0 .. $#data - 5) {
      $sum[$_] += $data[$_ + 5]
     }
   } else {
     dumpsums();
     $prevkey = $key;
     @sum = @data[5 .. $#data];
   }
}
dumpsums();

sub dumpsums {
  if ($prevkey) {
    print "$prevkey,", join(",", @sum), "\n";
  }
}

[download]

In reply to Re: Tabulating Data Across Multiple Large Files by Thelonius
in thread Tabulating Data Across Multiple Large Files by reds

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.