177 lines
5.8 KiB
Plaintext
177 lines
5.8 KiB
Plaintext
=head1 NAME
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DBD::File::Roadmap - Planned Enhancements for DBD::File and pure Perl DBD's
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Jens Rehsack - May 2010
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=head1 SYNOPSIS
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This document gives a high level overview of the future of the DBD::File DBI
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driver and groundwork for pure Perl DBI drivers.
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The planned enhancements cover features, testing, performance, reliability,
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extensibility and more.
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=head1 CHANGES AND ENHANCEMENTS
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=head2 Features
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There are some features missing we would like to add, but there is
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no time plan:
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=over 4
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=item LOCK TABLE
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The newly implemented internal common table meta storage area would allow
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us to implement LOCK TABLE support based on file system C<flock ()>
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support.
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=item Transaction support
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While DBD::AnyData recommends explicitly committing by importing and
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exporting tables, DBD::File might be enhanced in a future version to allow
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transparent transactions using the temporary tables of SQL::Statement as
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shadow (dirty) tables.
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Transaction support will heavily rely on lock table support.
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=item Data Dictionary Persistence
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SQL::Statement provides dictionary information when a "CREATE TABLE ..."
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statement is executed. This dictionary is preserved for some statement
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handle attribute fetches (as C<NULLABLE> or C<PRECISION>).
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It is planned to extend DBD::File to support data dictionaries to work
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on the tables in it. It is not planned to support one table in different
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dictionaries, but you can have several dictionaries in one directory.
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=item SQL Engine selecting on connect
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Currently the SQL engine selected is chosen during the loading of the module
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L<DBI::SQL::Nano>. Ideally end users should be able to select the engine
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used in C<< DBI->connect () >> with a special DBD::File attribute.
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=back
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Other points of view to the planned features (and more features for the
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SQL::Statement engine) are shown in L<SQL::Statement::Roadmap>.
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=head2 Testing
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DBD::File and the dependent DBD::DBM requires a lot more automated tests
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covering API stability and compatibility with optional modules
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like SQL::Statement.
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=head2 Performance
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Several arguments for support of features like indexes on columns
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and cursors are made for DBD::CSV (which is a DBD::File based driver,
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too). Similar arguments could be made for DBD::DBM, DBD::AnyData,
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DBD::RAM or DBD::PO etc.
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To improve the performance of the underlying SQL engines, a clean
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re-implementation seems to be required. Currently both engines are
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prematurely optimized and therefore it is not trivial to provide
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further optimization without the risk of breaking existing features.
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Join the DBI developers IRC channel at L<irc://irc.perl.org/dbi> to
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participate or post to the DBI Developers Mailing List.
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=head2 Reliability
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DBD::File currently lacks the following points:
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=over 4
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=item duplicate table names
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It is currently possible to access a table quoted with a relative path
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(a) and additionally using an absolute path (b). If (a) and (b) are
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the same file that is not recognized (except for
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flock protection handled by the Operating System) and two independent
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tables are handled.
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=item invalid table names
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The current implementation does not prevent someone choosing a
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directory name as a physical file name for the table to open.
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=back
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=head2 Extensibility
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I (Jens Rehsack) have some (partially for example only) DBD's in mind:
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=over 4
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=item DBD::Sys
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Derive DBD::Sys from a common code base shared with DBD::File which handles
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all the emulation DBI needs (as getinfo, SQL engine handling, ...)
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=item DBD::Dir
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Provide a DBD::File derived to work with fixed table definitions through the
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file system to demonstrate how DBI / Pure Perl DBDs could handle databases
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with hierarchical structures.
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=item DBD::Join
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Provide a DBI driver which is able to manage multiple connections to other
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Databases (as DBD::Multiplex), but allow them to point to different data
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sources and allow joins between the tables of them:
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# Example
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# Let table 'lsof' being a table in DBD::Sys giving a list of open files using lsof utility
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# Let table 'dir' being a atable from DBD::Dir
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$sth = $dbh->prepare( "select * from dir,lsof where path='/documents' and dir.entry = lsof.filename" )
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$sth->execute(); # gives all open files in '/documents'
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...
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# Let table 'filesys' a DBD::Sys table of known file systems on current host
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# Let table 'applications' a table of your Configuration Management Database
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# where current applications (relocatable, with mountpoints for filesystems)
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# are stored
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$sth = dbh->prepare( "select * from applications,filesys where " .
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"application.mountpoint = filesys.mountpoint and ".
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"filesys.mounted is true" );
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$sth->execute(); # gives all currently mounted applications on this host
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=back
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=head1 PRIORITIES
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Our priorities are focused on current issues. Initially many new test
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cases for DBD::File and DBD::DBM should be added to the DBI test
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suite. After that some additional documentation on how to use the
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DBD::File API will be provided.
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Any additional priorities will come later and can be modified by (paying)
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users.
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=head1 RESOURCES AND CONTRIBUTIONS
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See L<http://dbi.perl.org/contributing> for I<how you can help>.
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If your company has benefited from DBI, please consider if
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it could make a donation to The Perl Foundation "DBI Development"
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fund at L<http://dbi.perl.org/donate> to secure future development.
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Alternatively, if your company would benefit from a specific new
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DBI feature, please consider sponsoring it's development through
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the options listed in the section "Commercial Support from the Author"
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on L<http://dbi.perl.org/support/>.
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Using such targeted financing allows you to contribute to DBI
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development and rapidly get something specific and directly valuable
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to you in return.
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My company also offers annual support contracts for the DBI, which
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provide another way to support the DBI and get something specific
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in return. Contact me for details.
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Thank you.
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=cut
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