artist has asked for the wisdom of the Perl Monks concerning the following question:

Each subsequent change file has records mentioned to added/changed (L) or deleted (E) 
change1
=======
L|Key1 Values
L|Key2 Values
L|Key3 Values

change2
=============
E|Key2 
L|Key4 values

change3
===============
L|Key4 values
E|Key7
L|Key8 values

change4
=============
L|Key7 values
L|Key9 values
I like to combine all the records but which are deleted. For deletion the record has to be deleted after it has been added/changed. I have around 300,000 records and efficient methods would be good. What is the best approach I can take?

Thank you,
artist

Replies are listed 'Best First'.
•Re: Change files mechanism
by merlyn (Sage) on Jun 24, 2003 at 17:54 UTC 
    my %result;
# preusume @ARGV is loaded with the changeNN files in the right order
while (<>) {
  if (/^L\|(\S+)\s+(.*)/) {
    $result{$1} = $2;
  } elsif (/^E\|(\S+)/) {
    $result{$1} = undef;
  } else {
    warn "I don't understand: $_";
  }
}
for (sort keys %result) {
  my $value = $result{$_};
  if (defined $value) { # last thing was a change:
    print "L|$_ $value\n";
  } else { # last thing was a delete:
    print "E|$_\n";
  }
}

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    Untested, but I think I got the gist of your post.

    -- Randal L. Schwartz, Perl hacker
    Be sure to read my standard disclaimer if this is a reply.

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