Does this test for an empty hash use a lot of memory if the hash is big?
$nmail->relay('<>',1) unless keys %$hash_ref;

No, keys in scalar context just returns the number of elements of the hash; and the hash keeps score in its internal datastructure.

This is of course assuming we are talking about a normal hash. If the hash is tied, then it will depend on the implementation.

Abigail

Thanks for your reply.

I have managed to reduce some of the memory usage (because I'm able to process more of the log now) but my program is still crashing. I'm having a problem tying the hashes whose elements are arrays e.g.

tie %recipientqids, 'MLDBM', "/home/u752359/recipientqids.db", O_CREAT
+|O_RDWR, 0640 or die $!;
push(@{$recipientqids{$hostqid}},$recipient);
..
..
foreach $hostqid( @{$msgidqids{$msgid}}){
        foreach $recipient (@{$recipientqids{$hostqid}}){
                print STDERR "\nrecip= $recipient";
        }
}
[download]

doesn't print anything if I tie the recipientqids hash.

Is my syntax wrong, or can you not store these structures with MLDBM?

Thanks,

js1