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, the SQL::Statement(3) manpage for details on SQL::Statement and the DBD::CSV(3) manpage or the DBD::IniFile(3) manpage 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.

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.