NAME

DBD::File - Base class for writing DBI drivers

SYNOPSIS

 This module is a base class for writing other DBDs.
 It is not intended to function as a DBD itself.
 If you want to access flatfiles, use DBD::AnyData, or DBD::CSV,
 (both of which are subclasses of DBD::File).

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 for details on DBI, SQL::Statement for details on SQL::Statement and DBD::CSV or DBD::IniFile 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.

f_ext

This attribute is used for setting the file extension where (CSV) files are opened. There are several possibilities.

    DBI:CSV:f_dir=data;f_ext=.csv

In this case, DBD::File will open only table.csv if both table.csv and table exist in the datadir. The table will still be named table. If your datadir has files with extensions, and you do not pass this attribute, your table is named table.csv, which is probably not what you wanted. The extension is always case-insensitive. The table names are not.

    DBI:CSV:f_dir=data;f_ext=.csv/r

In this case the extension is required, and all filenames that do not match are ignored.

f_schema

This will set the schema name. Default is the owner of the folder in which the table file resides. undef is allowed.

    my $dbh = DBI->connect ("dbi:CSV:", "", "", {
        f_schema => undef,
        f_dir    => "data",
        f_ext    => ".csv/r",
        }) or die $DBI::errstr;

The effect is that when you get table names from DBI, you can force all tables into the same (or no) schema:

    my @tables $dbh->tables ();

    # no f_schema
    "merijn".foo
    "merijn".bar

    # f_schema => "dbi"
    "dbi".foo
    "dbi".bar

    # f_schema => undef
    foo
    bar

Defining f_schema to the empty string is equal to setting it to undef, this to enable the DSN to be dbi:CSV:f_schema=;f_dir=..

f_lock

With this attribute, you can force locking mode (if locking is supported at all) for opening tables. By default, tables are opened with a shared lock for reading, and with an exclusive lock for writing. The supported modes are:

0

Force no locking at all.

1

Only shared locks will be used.

2

Only exclusive locks will be used.

But see "NOWN BUGS" below.

f_encoding

With this attribute, you can set the encoding in which the file is opened. This is implemented using binmode $fh, ":encoding(<f_encoding)">.

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.

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

This module is currently maintained by

H.Merijn Brand < h.m.brand at xs4all.nl > and Jens Rehsack < rehsack at googlemail.com >

The original author is Jochen Wiedmann.

COPYRIGHT AND LICENSE

Copyright (C) 2009 by H.Merijn Brand & Jens Rehsack Copyright (C) 2004 by Jeff Zucker Copyright (C) 1998 by Jochen Wiedmann

All rights reserved.

You may freely distribute and/or modify this module under the terms of either the GNU General Public License (GPL) or the Artistic License, as specified in the Perl README file.

SEE ALSO

DBI, Text::CSV, Text::CSV_XS, SQL::Statement

cpanm DBI

perl -MCPAN -e shell
install DBI