Motional Monks,

For depressing-to-explain reasons, we're using an old DBM file (data_dbm_file) as a backup to a small sql database (data_db) of name/value pairs. Each time data_db is updated, the following sub routine is run:

    tie %data_hash, "SDBM_File", "data_dbm_file", O_RDWR|O_CREAT, 0666
+ || die "Cannot open file 'data_dbm_file': $!\n";
    %data_hash = ();
    $sqlSelect = "SELECT field1, field2 FROM $data_db";
    $sth = $dbh->prepare($sqlSelect) || die "Cannot prepare: " . $dbh-
+>errstr();
    $sth->execute() or die "Cannot execute: " . $sth->errstr();

    while (@data = $sth->fetchrow_array()) {
        my $data_to_store = crypt($data[1], $private_key);
        $data_hash{$data[0]} = $data_to_store;
    }
    untie %data_hash;
    $sth->finish();
[download]

And this is re-run every time there's a change to the data_db database. So, essentially, the DBM file gets completely re-written every time there's any change to the data_db database.

It seems to work just fine - the DBM file is checked on occasion and always mirrors the sql database.

BUT - there's always a but - if I ftp a copy of the data_dbm_file from the server onto my (Windows) PC, and open it in Notepad, among the long list of data I find this sort of thing:

bogA4dxaWfeMo:Namen_
bogA4dxaWfeMo:Namen_
bogA4dxaWfeMo:Namen
bogA4dxaWfeMo:Name
bogA4dxaWfeMo:Namen_0
bogA4dxaWfeMo:Namen_0
bogA4dxaWfeMo:Namen
bogA4dxaYbogA4dxaWfeMo:Name
bogA4dxaWfeMo:Name
bogA4dxaWfeMo:Namen
acbogA4dxaWfeMo:Namen
abogA4dxaWfeMo:Namen
[download]

Multiple entires with slight variations of old name/value pairs that were thought to be deleted long ago. There can be dozens of them for a single name. But they don't appear in a listing of the contents of the DBM file if we do:

tie %h, "DB_File", "data", O_RDWR|O_CREAT, 0666, $DB_HASH or die "Cann
+ot open file 'data': $!\n";
 
print "Content-type:text/html\n\n";
 
foreach my $key (sort keys %h) {
    print "<br>$key -> $h{$key}\n";
}
[download]

This outputs just the expected name/value pairs.

What is all this extra cruft? Is this due to something about our re-writing sub-routine? Or a typical result in a DBM file? Or something else?

Thanks.

---

In reply to Tie data hash to DBM file leaving massive cruft? by punch_card_don

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