NAME

DBD::File::Roadmap - Planned Enhancements for the DBD::File and Pure Perl DBD's

Jens Rehsack - May 2010

SYNOPSIS

This document gives a high level overview of the future of the DBD::File DBI driver and groundwork for pure Perl DBI drivers.

The planned enhancements cover features, testing, performance, reliability, extensibility and more.

CHANGES AND ENHANCEMENTS

Features

There're some features missing we would like to add (without time plan):

LOCK TABLE

The newly implemented internal common table meta storage area would allow us to implement a LOCK TABLE support based on file system flock () support.

Transaction support

While DBD::AnyData recommends explicitely committing by importing and exporting tables, DBD::File might be enhanced in a future version to allow transparent transactions using the temporary tables of SQL::Statement as shadow (dirty) table.

Transaction support will heavily rely on lock table support.

SQL Engine selecting on connect

Currently the SQL engine to use is choosen during the load of the module DBI::SQL::Nano. Ideally end users will be enabled to select the engine to use in DBI->connect () with a special DBD::File attribute.

Testing

DBD::File and the dependent DBD::DBM requires much more automated tests, covering stability of current API and compatibility with optional modules like SQL::Statement.

Performance

Several discussions about support for features like index on columns or cursors are made for DBD::CSV (which is a DBD::File based driver, too). Same discussions could be made for DBD::DBM, DBD::AnyData, DBD::RAM or DBD::PO etc.

To improve the performance of the underlying SQL engines, a clean reimplementation seems to be required. Currently both engines are premature optimized and therefore it's not trivial to optimize even more without high risk of breaking running features.

Join the DBI developers IRC channel at irc://irc.perl.org/dbi to participate or write us to the DBI Developers Mailing List.

Reliability

DBD::File currently lacks following points:

duplicate table names

It's currently possible to access a table quoted with a relative path (a) and second time using an absolute path (b). If the absolute path of (a) points to the path of (b), it's not recognized (except flock protection handled by the Operating System) and two independent tables are handled.

invalid table names

Current implementation doesn't protect from choosing a directory name as physical file name for the table to open.

Extensibility

I (Jens Rehsack) have some (partially for example only) DBD's in mind:

DBD::Sys

Derive DBD::Sys from a common code base shared with DBD::File which handled all emulation DBI needs (as getinfo, SQL engine handling, ...)

DBD::Dir

Provide a DBD::File derived to walk with fixed table definitions through the file system to demonstrate how DBI / Pure Perl DBD's could handle databases with hierarchical structues.

DBD::Join

Provide a DBI driver which is able to manage multiple connections to other Databases (as DBD::Multiplex), but allow them to point to different data sources and allow joins between the tables of them:

  # Example
  # Let table 'lsof' being a table in DBD::Sys giving a list of open files using lsof utility
  # Let table 'dir' being a atable from DBD::Dir
  $sth = $dbh->prepare( "select * from dir,lsof where path='/documents' and dir.entry = lsof.filename" )
  $sth->execute(); # gives all open files in '/documents'
  ...

  # Let table 'filesys' a DBD::Sys table of known file systems on current host
  # Let table 'applications' a table of your Configuration Management Database
  #  where current applications (relocatable, with mountpoints for filesystems)
  #  are stored
  $sth = dbh->prepare( "select * from applications,filesys where " .
                       "application.mountpoint = filesys.mountpoint and ".
                       "filesys.mounted is true" );
  $sth->execute(); # gives all currently mounted applications on this host

PRIORITIES

Our priorities are localized to our current issues. At first, many new test cases for DBD::File and DBD::DBM should be added to DBI test suite. After it, some additional documentation how to use the DBD::File API will be provided.

Any additional priorities will come later and can be modified by (paying) users.

RESOURCES AND CONTRIBUTIONS

See http://dbi.perl.org/contributing for how you can help.

If your company has benefited from the DBI, please consider if it could make a donation to The Perl Foundation "DBI Development" fund at http://dbi.perl.org/donate to secure future development.

Alternatively, if your company would benefit from a specific new DBI feature, please consider sponsoring its development through the options listed in the section "Commercial Support from the Author" on http://dbi.perl.org/support/.

Using such targeted financing allows you to contribute to DBI development and rapidly get something specific and directly valuable to you in return.

My company also offers annual support contracts for the DBI, which provide another way to support the DBI and get something specific in return. Contact me for details.

Thank you.

cpanm DBI

perl -MCPAN -e shell
install DBI