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Multi Level DBM file

Posted on 2000-02-28
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Last Modified: 2010-03-05
I am using a multi level data structure in my Perl script, for example:

%hash {};

$hash{name}{family}[age]{sex}

I want to store the data structure in a DBM file. apparently DBM files can store only key, value pairs and not intricate data structures.
I have tried using MLDBM from CPAN but to no avail, either due to my lack of  know-how or to another problem.

Please advise.

Thanks,

Shay
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Question by:shayb022800
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Expert Comment

by:makerp
ID: 2564764
it looks like you may have an eaiser life using a database and using dbi/dbd ?. you will then get all of the benifits of sql etc .
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Expert Comment

by:guadalupe
ID: 2565143
What about a text delimited file which can be interfaced with SQL?  The module Sprite has been a favorite of mine for database like work on a small scale.

http://www.perl.com/CPAN-local/modules/by-module/Sprite/

If this sounds appealing I can help with code though the example included is rather good...
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Expert Comment

by:alien_life_form
ID: 2568863
Greetings.

In alternative, you could use composite keys:

$hash{"$name,$family,$age,$sex"}=...

Or even:

$key=join("\007",($name,$family,$age,$sex);
$hash{$key}=...;

If you are doing more complex things, then the suggested DBMS stuff is the way to go.

Cheers,

  alf

 
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Accepted Solution

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bitsrfr earned 50 total points
ID: 2583326
I am doing exactly what you speak of.  You must use the package MLDBM.  Go down that path - the correct one - and ask questions when you come to problems implementing that.  I will help you...
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Expert Comment

by:alien_life_form
ID: 2587580
It's always nice to get in touch with people which are able, without any uncertainty, to thread  'the correct path'...

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Expert Comment

by:bitsrfr
ID: 2587798
hehe, yes, it is a gift. :-)

Shay,

   Perhaps where you ran into problems with MLDBM is that "Adding or altering substructures to a hash value is not entirely transparent in current perl.  If you want to store a reference or modify an existing reference value in the DBM, it must first be retrieved and stored in a temporary variable for further modifications.  
In particular, something like this will NOT work properly:

$mldb{key}{subkey}[3] = 'stuff';        # won't work

Instead, that must be written as:

$tmp = $mldb{key};                      # retrieve value
$tmp->{subkey}[3] = 'stuff';
$mldb{key} = $tmp# store value
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