in reply to Weirdness when reading from DBM file

Warning: Completely and utterly untested. 
use DBM::Deep;

my $dbh = get_dbh();

# This is the magic. :-)
my $db = DBM::Deep->new( 'db_file.db' );

my @keys = 
    qw(employee_id firstname lastname title dept salary date_hired);
my @values = @{$dbh->selectall_arrayref($query)};

for my $v (@values){
    my @vals = @$v; # one ID per array
    for (@vals){
        $_ = '-' unless $_; # in case of empty fields
    }

    # Map is a wonderful piece of magic. Look really really hard at
    # this code before freaking out.
    $db->{$vals[0]} = {
        (map {
            $keys[$_] => $vals[$_];
        } 0 .. $#keys)
    };
}

[download]
My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

Replies are listed 'Best First'.
Re^2: Weirdness when reading from DBM file
by mojodaddy (Pilgrim) on Sep 12, 2007 at 01:08 UTC
    Just wanted to report back on my results, which were phenomenal! This script writes the MySQL database to the DBM file: 
    #!/usr/bin/perl -w

use strict;

use Mojo::DB;
use DBM::Deep;

$| = 1;

my $dbh = get_dbh();
die "No filename argument provided" unless @ARGV;
my $file = shift @ARGV;

unlink $file;

# This is the magic. :-)
my $db = DBM::Deep->new( $file );

tie my %IDS, 'DBM::Deep', $file or die "$!";

my @keys = qw(employee_id firstname lastname title dept salary date_hi
+red);

my $keys = join(', ', @keys);
my $query = "select $keys from employee_data";
my @values = @{$dbh->selectall_arrayref($query)};

for my $v (@values){
    my @vals = @$v; # one ID per array
    for (@vals){
        $_ = '-' unless $_;
    }
    $db->{$vals[0]} = {
        (map {
            $keys[$_] => $vals[$_];
        } 0 .. $#keys)
    };
}

    [download]
    and this script reads the data back out: 
    #!/usr/bin/perl -w

use strict;
use DBM::Deep;

$| = 1;

die "No filename argument provided" unless @ARGV;
my $file = shift @ARGV;

tie my %IDS, 'DBM::Deep', $file or die "$!";

while (my($k, $v) = each %IDS){
    print "\n$k :\n";
    while (my ($k, $v) = each %{$v}){
        print "$k => $v\n";
    }
}

    [download]
    It really works like a dream, thank you so much. The nice thing, too, is that I almost understand how it works! I'm even going to leave your comment about "this is the magic" in there to remind me. : )

    Any technology sufficiently advanced is indistinguishable from a Perl script.
[reply]
[d/l]
[select]
      *smiles* I'm glad it worked out for you. If you run into any problems with DBM::Deep, please let me know.

      As for map, it's conceptually pretty simple. You're used to functions taking a single thing as an argument and returning a single thing as a result. Map takes an action and a list of things as arguments, does the action to each of the things in turn, and returns the list of actioned things as a result.

      In the code above, what I'm doing is taking a list of indices and inflating each one into a key-value pair. Then, I'm using the fact that a hash can be assigned a list of key-value pairs to create my hash. Does that help make more sense?

      My criteria for good software:
      1. Does it work?
      2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
[reply]
Re^2: Weirdness when reading from DBM file
by mojodaddy (Pilgrim) on Sep 12, 2007 at 00:24 UTC
    Very nice, thank you for that. I really do think of map as a kind of magic. It reminds me of this quote:

    "Any technology sufficiently advanced is indistinguishable from a Perl script."

    Hey, I think I just found my clever signature line. But if someone else is already using it, let me know...

[reply]

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