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DBD::File::Roadmap(3pm)        User Contributed Perl Documentation	  DBD::File::Roadmap(3pm)

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

       Jens Rehsack - May 2010

       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.

       There are some features missing we would like to add, but there is no time plan:

	   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

	   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.

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

       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 reimplementation 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.

       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.

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

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

	   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.

	   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

       Our priorities are focussed 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.

       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

       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.

perl v5.12.3				    2010-07-02			  DBD::File::Roadmap(3pm)
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