# https://www.perlmonks.org/?node_id=11110379
# usage: perl search_db_chunk.pl > Outfile.txt

use strict;
use warnings;
use KyotoCabinet;
use MCE;

# construct the database object
my $db = KyotoCabinet::DB->new();
my $cur;

my $mce = MCE->new(
    max_workers => MCE::Util::get_ncpu(),
    chunk_size  => 7,
    init_relay  => 1,

    user_begin => sub {
        # open the database
        if (! $db->open('db.kch#msiz=128m', $db->OREADER | $db->ONOLOCK)) {
            die "open error (db): ", $db->error;
        }
        $cur = $db->cursor;
    },

    user_end => sub {
        # close the database
        $cur->disable;
        $db->close;
    },

    user_func => sub {
        my ( $mce, $chunk_ref, $chunk_id ) = @_;
        my %ret; chomp @$chunk_ref;

        $cur->jump; # first record
        while ( my ($key, $val) = $cur->get(1) ) {
            for ( @$chunk_ref ) {
                $ret{$_} .= ",$key" if index($val, $_) >= 0;
            }
        }

        # output serially, one worker at a time
        MCE::relay {
            for ( @$chunk_ref ) {
                print "$_\t", substr($ret{$_}, 1), "\n" if $ret{$_};
            }
        };
    }
);

$mce->process('peptides.txt');
$mce->shutdown;