DBD::File::HowTo(3)

💖 DBD::File::HowTo — the guide to making your own DBD::File-based driver 💖

okay bestie, so this is the DBD::File::HowTo page from the User Contributed Perl Documentation, and it's literally your step-by-step roadmap for building a whole new DBD::File based DBD. grab a snack, we're doing this 🍓

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✨ NAME ✨

DBD::File::HowTo — the guide to create a DBD::File based driver. no cap, that's the whole assignment 💅

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🎀 SYNOPSIS 🎀

like, go read these first, queen:

perldoc DBD::File::HowTo
perldoc DBI
perldoc DBI::DBD
perldoc DBD::File::Developers
perldoc DBI::DBD::SqlEngine::Developers
perldoc DBI::DBD::SqlEngine
perldoc SQL::Eval
perldoc DBI::DBD::SqlEngine::HowTo
perldoc SQL::Statement::Embed
perldoc DBD::File
perldoc DBD::File::HowTo
perldoc DBD::File::Developers

(yes perldoc DBD::File::HowTo shows up twice, that's not a typo, that's just how it is 🙈)

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🌈 DESCRIPTION 🌈

So this doc gives you a full step-by-step guide on how to create a brand new DBD::File based DBD. It lowkey expects that you carefully read the DBI documentation, that you're familiar with DBI::DBD, and that you've read and actually understood DBD::ExampleP. no skimming, bestie 😤

This one is for experienced developers who are really sure they need to invest the time into writing a new DBI Driver. Writing a DBI Driver is not a weekend project, and it's not a lil easy job for hobby coders after work. Expect one or two man-month of time for the first start. it's giving commitment 💀

And if you're still reading after all that? you should be able to sing the rules of "CREATING A NEW DRIVER" in DBI::DBD. like, from memory. karaoke style 🎤

And obvi, DBD::File is a DBI::DBD::SqlEngine, and you surely read DBI::DBD::SqlEngine::HowTo before continuing here. right? right? 👀

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👑 CREATING DRIVER CLASSES 👑

First vibe check: do you even have an entry in DBI's DBD registry? For this guide, a prefix of "foo_" is assumed. okay so we're doing foo. iconic.

🧚 Sample Skeleton

package DBD::Foo;

use strict;
use warnings;
use base qw(DBD::File);

use DBI ();

our $VERSION = "0.001";

package DBD::Foo::dr;

our @ISA = qw(DBD::File::dr);
our $imp_data_size = 0;

package DBD::Foo::db;

our @ISA = qw(DBD::File::db);
our $imp_data_size = 0;

package DBD::Foo::st;

our @ISA = qw(DBD::File::st);
our $imp_data_size = 0;

package DBD::Foo::Statement;

our @ISA = qw(DBD::File::Statement);

package DBD::Foo::Table;

our @ISA = qw(DBD::File::Table);

1;

Tiny, right?? like literally so smol 🥺 and all you have now is a DBD named foo which will be able to deal with temporary tables, as long as you use SQL::Statement. In DBI::SQL::Nano environments, this DBD can do nothing. periodt. 💀

🦋 Start over

Based on DBI::DBD::SqlEngine::HowTo, we're now having a driver which could do basic things. Of course, it should now derive from DBD::File instead of DBI::DBD::SqlEngine, shouldn't it? yes bestie, glow up time ✨

DBD::File extends DBI::DBD::SqlEngine to deal with any kind of files. In principle, the only extensions required are to the table class:

package DBD::Foo::Table;

sub bootstrap_table_meta {
    my ($self, $dbh, $meta, $table) = @_;

    # initialize all $meta attributes which might be relevant for
    # file2table

    return $self->SUPER::bootstrap_table_meta ($dbh, $meta, $table);
    }

sub init_table_meta {
    my ($self, $dbh, $meta, $table) = @_;

    # called after $meta contains the results from file2table
    # initialize all missing $meta attributes

    $self->SUPER::init_table_meta ($dbh, $meta, $table);
    }

And in case "DBD::File::Table::open_file" doesn't open the files the way the driver needs it to? override it! main character energy, go off 👑

sub open_file {
    my ($self, $meta, $attrs, $flags) = @_;
    # ensure that $meta->{f_dontopen} is set
    $self->SUPER::open_file ($meta, $attrs, $flags);
    # now do what ever needs to be done
    }

Combined with the methods implemented using the SQL::Statement::Embed guide, the table is full working and you could try a start over. slay 💅

🫶 User comfort

"DBD::File" since 0.39 consolidates all persistent meta data of a table into a single structure stored in $dbh->{f_meta}. With "DBD::File" version 0.41 and "DBI::DBD::SqlEngine" version 0.05, this consolidation moves to DBI::DBD::SqlEngine. It's still the $dbh->{$drv_prefix . "_meta"} attribute which cares, so what you learned at this place before, is still valid. nothing got deleted, bestie, just rehomed 🏠

sub init_valid_attributes {
    my $dbh = $_[0];

    $dbh->SUPER::init_valid_attributes ();

    $dbh->{foo_valid_attrs} = { ... };
    $dbh->{foo_readonly_attrs} = { ...  };

    $dbh->{foo_meta} = "foo_tables";

    return $dbh;
    }

See updates at "User comfort" in DBI::DBD::SqlEngine::HowTo. iykyk 📚

⭐ Testing

Now you should have your own DBD::File based driver. Was easy, wasn't it? 🥰 But does it work well? Prove it by writing tests — and remember to use dbd_edit_mm_attribs from DBI::DBD to ensure testing even rare cases. test the weird edge cases, they're the ones that humble you 😭

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💜 AUTHOR 💜

This guide is written by Jens Rehsack. DBD::File is written by Jochen Wiedmann and Jeff Zucker. legends only 👑

The module DBD::File is currently maintained by

H.Merijn Brand < perl5 at tux.freedom.nl > and Jens Rehsack < rehsack at googlemail.com >

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🌸 COPYRIGHT AND LICENSE 🌸

Copyright (C) 2010-2026 by H.Merijn Brand</> & Jens Rehsack</>

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.

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and that's the whole thing, bestie!! go forth and write your driver, i believe in you fr fr 🫶💖

perl v5.42.3 · 2026-10-19 — signing off from the DBD::File::HowTo(3) page, mwah 💋</>