The problem with huge and fast is not disk space, it's memory space. The software that performs the mailings all runs daemonized, since start-up is our biggest penalty, having 5 500M(++) daemons laying around is not funny.

Ah, I misunderstood what you meant by 'huge'. Still, if memory is your concern, that sounds like an even better reason to use a DB and let the DB handle the intersection calulations. BTW, what solution for intersection handling results in a 500MB memory footprint?! I'd like to know so I can avoid that myself.

For the purpose of blacklisting, it might be small-and-fast to convert your list of addresses into a hash instead. Assuming you've already populated @blacklist and @address, your intersection sub might look like:

my @BlackListed = intersect_of(\@blacklist, \@address);
sub intersect_of ($$) {
   my $a, $b = @_;
   my (%set_a, %set_b);
   
   ## put the larger set in %set_a
   if (@$a > @$b) {
      %set_a = map { $_ => undef } @$a;
      %set_b = map { $_ => undef } @$b;
   else {
      %set_a = map { $_ => undef } @$b;
      %set_b = map { $_ => undef } @$a;
   }
   
   my @intersect;

   ## iterate through smaller set
   for (keys %set_b) {
      push @intersect, $_ if exists $set_a{$_}
   }
   
   return @intersect;
}
[download]

This exact code is untested, but I have used code like it for whitelist/blacklist processing with address list files of about 5M each, and it performed quite acceptably. YMMV, of course.

---

In reply to Re^3: Finding an intersection of two sets, lean and mean by radiantmatrix
in thread Finding an intersection of two sets, lean and mean by Sinister

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

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.