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

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


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 Copyright (C) 1998 by


    Jochen Wiedmann

    Am Eisteich 9

    72555 Metzingen

    Germany

    Email: joe@ispsoft.de

    Phone: +49 7123 14887

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), the Text::CSV_XS(3) manpage, the SQL::Statement(3) manpage

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