DBD::File(3)

NAME
DBD::File - Base class for writing DBI drivers for plain files

SYNOPSIS
    use DBI;
    $dbh = DBI->connect("DBI:File:f_dir=/home/joe/csvdb")
        or die "Cannot connect: " . $DBI::errstr;
    $sth = $dbh->prepare("CREATE TABLE a (id INTEGER, name CHAR(10))")
        or die "Cannot prepare: " . $dbh->errstr();
    $sth->execute() or die "Cannot execute: " . $sth->errstr();
    $sth->finish();
    $dbh->disconnect();

DESCRIPTION
The DBD::File module is not a true DBI driver, but an abstract base class for deriving concrete DBI drivers from it. The implication is, that these drivers work with plain files, for example CSV files or INI files. The module is based on the SQL::Statement module, a simple SQL engine.

See DBI(3) for details on DBI, SQL::Statement(3) for details on SQL::Statement and DBD::CSV(3) or DBD::IniFile(3) for example drivers.

  Metadata
The following attributes are handled by DBI itself and not by DBD::File, thus they all work like expected:

    Active
    ActiveKids
    CachedKids
    CompatMode             (Not used)
    InactiveDestroy
    Kids
    PrintError
    RaiseError
    Warn                   (Not used)

The following DBI attributes are handled by DBD::File:

AutoCommit
    Always on

ChopBlanks
    Works

NUM_OF_FIELDS
    Valid after "$sth-"execute>

NUM_OF_PARAMS
    Valid after "$sth-"prepare>

NAME
    Valid after "$sth-"execute>; undef for Non-Select statements.

NULLABLE
    Not really working, always returns an array ref of one's, as DBD::CSV doesn't verify input data. Valid after "$sth-"execute>; undef for Non-Select statements.

These attributes and methods are not supported:

    bind_param_inout
    CursorName
    LongReadLen
    LongTruncOk

Additional to the DBI attributes, you can use the following dbh attribute:

f_dir
    This attribute is used for setting the directory where CSV files are opened. Usually you set it in the dbh, it defaults to the current directory ("."). However, it is overwritable in the statement handles.

  Driver private methods

data_sources
    The "data_sources" method returns a list of subdirectories of the current directory in the form "DBI:CSV:f_dir=$dirname".

    If you want to read the subdirectories of another directory, use

        my($drh) = DBI->install_driver("CSV");
        my(@list) = $drh->data_sources('f_dir' => '/usr/local/csv_data' );

list_tables
    This method returns a list of file names inside $dbh->{'f_dir'}. Example:

        my($dbh) = DBI->connect("DBI:CSV:f_dir=/usr/local/csv_data");
        my(@list) = $dbh->func('list_tables');

    Note that the list includes all files contained in the directory, even those that have non-valid table names, from the view of SQL. See "Creating and dropping tables" above.

TODO

Joins
    The current version of the module works with single table SELECT's only, although the basic design of the SQL::Statement module allows joins and the likes.

Table name mapping
    Currently it is not possible to use files with names like "names.csv". Instead you have to use soft links or rename files. As an alternative one might use, for example a dbh attribute 'table_map'. It might be a hash ref, the keys being the table names and the values being the file names.

KNOWN BUGS

•   The module is using flock() internally. However, this function is not available on all platforms. Using flock() is disabled on MacOS and Windows 95: There's no locking at all (perhaps not so important on MacOS and Windows 95, as there's a single user anyways).

AUTHOR AND COPYRIGHT
This module is currently maintained by

      Jeff Zucker
      <jeff@vpservices.com>

The original author is Jochen Wiedmann.

Copyright (C) 1998 by Jochen Wiedmann

All rights reserved.

You may distribute this module under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.

SEE ALSO
DBI(3), Text::CSV_XS(3), SQL::Statement(3)