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
LongTruncOkAdditional 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=.csvIn this case, DBD::File will open only
table.csvif bothtable.csvandtableexist in the datadir. The table will still be namedtable. If your datadir has files with extensions, and you do not pass this attribute, your table is namedtable.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/rIn 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.
undefis 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 $dbh->tables (); # no f_schema "merijn".foo "merijn".bar # f_schema => "dbi" "dbi".foo "dbi".bar # f_schema => undef foo bar
Driver private methods
- data_sources
-
The
data_sourcesmethod returns a list of subdirectories of the current directory in the form "DBI:CSV:f_dir=$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.