Limits of DB_File with Btree algorithm

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

When I uncomment lines 3-5, this code doesn't work. Why? When I uncomment the last 5 lines, it works. Is Storable the correct approach here? I'm going to write a hash to disk that will act like a miniature database. What should I read to learn more about persistent data structures?

use strict;
my %testline;
# use DB_File;
# tie (%testline, 'DB_File', 'testline.db', O_RDWR|O_CREAT,
#   0666, $DB_BTREE) or die "Cannot tie:$!";
 
push @{ $testline{a} }, {
                          uri   => 'http://',
                          name  => 'barney',
                          state => 'MI'
                        };
push @{ $testline{a} }, {
                          uri   => 'ftp://',
                          name  => 'jade',
                          state => 'NM'
                        };
 
# use Storable;
# store \%testline, 'filetest';
# my $hashref = retrieve('filetest');
# use Data::Dumper;
# print Data::Dumper->Dump([$hashref],['hashref']);
[download]

Comment on Limits of DB_File with Btree algorithm Download Code

Replies are listed 'Best First'.
Re (tilly) 1: Limits of DB_File with Btree algorithm by tilly (Archbishop) on Feb 05, 2001 at 22:14 UTC
What gets stored is a stringified version of your data. Since references involve internal program state, it is not easy to transparently pass references (eg anon hashes) between programs. See MLDBM for a solution.	[reply]
Re: Limits of DB_File with Btree algorithm by runrig (Abbot) on Feb 05, 2001 at 22:12 UTC
DB_File can not store complex data structures as values, only simple scalar values (i.e. strings, numbers) for each hash key. Therefore you can not store a hash of arrays of hashes. Unless you can serialize your value in some way (e.g. create a delimited string value out of the array of hashes that you're trying to store for each value), then Storable is the way to go. Update: Oh, neat, I didn't know about MLDBM, you learn something all the time around here :)	[reply]