---------- Forwarded message ----------
From: Brendan LeFebvre <[EMAIL PROTECTED]>
Date: Sep 30, 2005 9:59 PM
Subject: Re: DB_File btree losing key values on reload
To: Jim Schueler <[EMAIL PROTECTED]>, [email protected]
Hi Jim,
Thanks for writing.
It turns out the problem was that I overrode the compare function (to
make it case-insensitive) for the btree sort in the script that
created it. What I did not realize is that that same function override
must be specified in any additional scripts that use the same database
file. Once I copied the relevant lines over to my reader program
everything worked fine.
BL
On 9/30/05, Jim Schueler <[EMAIL PROTECTED]> wrote:
> Since my experience with ActiveState is minimal, I would've let someone else
> respond. But I never saw another response.
>
> I'm under the impression that DB_File uses legacy libraries of Berkeley
> 1.86. gdb_file is slightly more up-to-date. But I would recommend either
> using the Storable module or BerkeleyDB module. BerkeleyDB, like db_file,
> is file based; whereas Storable requires loading and writing the entire
> table.
>
> For 3600 name/value pairs, as shown in your example, marshalling an
> associative array using Storable is probably sufficient. Storable can also
> be applied to a custom object that incorporates your comparator routine.
>
> BerkeleyDB has commercial restrictions in addition to the disadvantage that
> its objects are not tied. I've extended BerkeleyDB so that the constructors
> return tied objects. My package BerkeleyDB::Lite is available on CPAN
> (BerkeleyDB-Lite-1_1.tar.gz). But the implementation is trivial to do the
> same thing with ActiveState.
>
> Jim Schueler
>
> On Mon, 26 Sep 2005 06:23:52 -0400, Brendan LeFebvre wrote
> > Hello all,
> >
> > I am having trouble with a DB_File in btree mode. It contains about 3600
> > keys.
> >
> > The script to generate the file is as follows (changed variable
> > names to generics for clarity):
> >
> > --- BEGIN BTREE GENERATOR ---
> >
> > use warnings;
> > use strict;
> > use DB_File;
> > my %hash = ();
> > $DB_BTREE->{'compare'} = \&cmp_casefree;
> >
> > sub cmp_casefree { my ($a,$b) = @_; lc($a) cmp lc($b) }
> > # override default compare function so that, e.g.,
> > # "du Pont" will go between "DuO..." and "DuQ..." instead of at the end
> >
> > tie %hash, "DB_File", "btree.dat", 0777, 0777, $DB_BTREE or die
> > "Cannot open file: $!";
> >
> > $hash{"Key1"} = "Value1";
> >
> > ... snip ...
> >
> > $hash{"Key3600"} = "Value3600";
> >
> > untie %hash;
> >
> > --- END BTREE GENERATOR ---
> >
> > OK, now I have a separate script that ties a hash to the file and simply
> > iterates through, printing all key-value pairs:
> >
> > --- BEGIN BTREE READER ---
> >
> > use strict;
> > use DB_File;
> > use Fcntl;
> >
> > # Initialize and load database arrays
> >
> > my %hash = ();
> >
> > tie %hash, "DB_File", "btree.dat", 0777, 0777, $DB_BTREE or die
> > "Cannot open file: $!"; foreach my $key (keys %hash) { print "$key
> > -> $hash{$key}\n"; }; untie %hash;
> >
> > print "done.\n";
> >
> > --- END BTREE READER ---
> >
> > Re-directing the reader's output to a text file and looking it over,
> > I see that some of the values are missing.
> >
> > For instance, where I expect to see:
> > Key35 -> Value35
> >
> > I will instead see:
> > Key35 ->
> >
> > A quick analysis reveals it to be just over 100 values missing out
> > of the 3600, some isolated but many in consecutive chunks of approx.
> > 5-10 keys.
> >
> > After re-running the generate script and then the reader script, the
> > same values are missing every time. So, while this error is baffling,
> > it is at least reproducible, and that comforts me. :)
> >
> > But here's the interesting part: if I put the reader code at the
> > bottom of the generator script-- that is, immediately after making
> > the file and untying %hash, I create a new hash %hash2 and tie the
> > file to it, then read across all keys-- every value is where it
> > should be.
> >
> > This is ActivePerl 5.8.7 build 813, with DB_File 1.811, both latest
> > available at this time, so far as I know. I hope someone can help
> > me. Thanks for reading. Let me know if any more information is needed.
> >
> > BL
>
>
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> Open WebMail Project (http://openwebmail.org)
>
>
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