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database/perl/vendor/lib/DBD/File/Roadmap.pod

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+=head1 NAME
+
+DBD::File::Roadmap - Planned Enhancements for DBD::File and pure Perl DBD's
+
+Jens Rehsack - May 2010
+
+=head1 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.
+
+=head1 CHANGES AND ENHANCEMENTS
+
+=head2 Features
+
+There are some features missing we would like to add, but there is
+no time plan:
+
+=over 4
+
+=item LOCK TABLE
+
+The newly implemented internal common table meta storage area would allow
+us to implement LOCK TABLE support based on file system C<flock ()>
+support.
+
+=item 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.
+
+=item 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 C<NULLABLE> or C<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.
+
+=item SQL Engine selecting on connect
+
+Currently the SQL engine selected is chosen during the loading of the module
+L<DBI::SQL::Nano>. Ideally end users should be able to select the engine
+used in C<< DBI->connect () >> with a special DBD::File attribute.
+
+=back
+
+Other points of view to the planned features (and more features for the
+SQL::Statement engine) are shown in L<SQL::Statement::Roadmap>.
+
+=head2 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.
+
+=head2 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 L<irc://irc.perl.org/dbi> to
+participate or post to the DBI Developers Mailing List.
+
+=head2 Reliability
+
+DBD::File currently lacks the following points:
+
+=over 4
+
+=item 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.
+
+=item invalid table names
+
+The current implementation does not prevent someone choosing a
+directory name as a physical file name for the table to open.
+
+=back
+
+=head2 Extensibility
+
+I (Jens Rehsack) have some (partially for example only) DBD's in mind:
+
+=over 4
+
+=item 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, ...)
+
+=item 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.
+
+=item 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
+
+=back
+
+=head1 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.
+
+=head1 RESOURCES AND CONTRIBUTIONS
+
+See L<http://dbi.perl.org/contributing> for I<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 L<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 L<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.
+
+=cut