#!/usr/bin/perl

use strict;
use warnings;

use Benchmark ':hireswallclock';
use DB_File ();

my $DB_FILE1;
my $DB_FILE2;


my $NUM_RECORDS = 50_000;
my $NUM_KEYS    = 1000;

setup_dbfile();

Benchmark::cmpthese(
    10,
    {
        'original' => \&benchmark_dbfile1,
        'preprocess'   => \&benchmark_dbfile2
    }
);



sub benchmark_dbfile1 {

    foreach my $value ( 1 .. $NUM_RECORDS ) {

        my $key = int(rand($NUM_KEYS));

        if ( exists $DB_FILE1->{$key} ) {
            $DB_FILE1->{$key} .= ",$value";
        }
        else {
            $DB_FILE1->{$key} = $value;
        }

    }
}

sub benchmark_dbfile2 {

    my %preprocess = ();
    foreach my $value ( 1 .. $NUM_RECORDS ) {

        my $key = int(rand($NUM_KEYS));
        push @{ $preprocess{$key} }, $value ;
    }

    while (my ($key, $val_list) = each %preprocess) {

        my $value = join ",", @$val_list;

        if ( exists $DB_FILE2->{$key} ) {
            $DB_FILE1->{$key} .= ",$value";
        }
        else {
            $DB_FILE2->{$key} = $value;
        }

    }
}

sub setup_dbfile {

  {
    unlink 'berkeley.db1';  
    my %data;
    tie %data, 'DB_File', 'berkeley.db1' or die "$!";
    $DB_FILE1 = \%data;
  }
  {
    unlink 'berkeley.db2';  
    my %data;
    tie %data, 'DB_File', 'berkeley.db2' or die "$!";
    $DB_FILE2 = \%data;
  }
}