DBD::File::Roadmap - phpMan

NAME
    DBD::File::Roadmap - Planned Enhancements for 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 are some features missing we would like to add, but there is no
    time plan:

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

    Transaction support
        While DBD::AnyData recommends explicitly 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) tables.

        Transaction support will heavily rely on lock table support.

    Data Dictionary Persistence
        SQL::Statement provides dictionary information when a "CREATE TABLE
        ..." statement is executed. This dictionary is preserved for some
        statement handle attribute fetches (as "NULLABLE" or "PRECISION").

        It is planned to extend DBD::File to support data dictionaries to
        work on the tables in it. It is not planned to support one table in
        different dictionaries, but you can have several dictionaries in one
        directory.

    SQL Engine selecting on connect
        Currently the SQL engine selected is chosen during the loading of
        the module DBI::SQL::Nano. Ideally end users should be able to
        select the engine used in "DBI->connect ()" with a special DBD::File
        attribute.

    Other points of view to the planned features (and more features for the
    SQL::Statement engine) are shown in SQL::Statement::Roadmap.

  Testing
    DBD::File and the dependent DBD::DBM requires a lot more automated tests
    covering API stability and compatibility with optional modules like
    SQL::Statement.

  Performance
    Several arguments for support of features like indexes on columns and
    cursors are made for DBD::CSV (which is a DBD::File based driver, too).
    Similar arguments 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
    re-implementation seems to be required. Currently both engines are
    prematurely optimized and therefore it is not trivial to provide further
    optimization without the risk of breaking existing features.

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

  Reliability
    DBD::File currently lacks the following points:

    duplicate table names
        It is currently possible to access a table quoted with a relative
        path (a) and additionally using an absolute path (b). If (a) and (b)
        are the same file that is not recognized (except for flock
        protection handled by the Operating System) and two independent
        tables are handled.

    invalid table names
        The current implementation does not prevent someone choosing a
        directory name as a 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
        handles all the emulation DBI needs (as getinfo, SQL engine
        handling, ...)

    DBD::Dir
        Provide a DBD::File derived to work with fixed table definitions
        through the file system to demonstrate how DBI / Pure Perl DBDs
        could handle databases with hierarchical structures.

    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 focused on current issues. Initially many new test
    cases for DBD::File and DBD::DBM should be added to the DBI test suite.
    After that some additional documentation on 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 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 it's 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.