Matthew Simon Cavalletto

NAME

DBIx::DBO2::ReadMe - Getting Started with DBIx::DBO2

SYNOPSIS

  package MyRecord;
  use DBIx::DBO2::Record '-isasubclass';
  my $sql_engine = DBIx::SQLEngine->new( $dsn, $user, $pass );
  
  MyRecord->table(
    DBIx::DBO2::Table->new(name=>'myrecords', datasource=>$sql_engine)
  );
  
  package main;
  my $results = MyRecord->fetch_all;
  foreach my $record ( $results->records ) {
    if ( $record->{age} > 20 ) {
      $record->{status} = 'adult';
      $record->save_row;
    }
  }

DESCRIPTION

DBIx::DBO2 is an object-relational mapping framework (or perhaps a relational-object mapping framework, if I understand the distinction correctly) that facilitates the development of Perl classes whose objects are stored in a SQL database table.

INSTALLING

You should be able to install this module using the CPAN shell interface:

  perl -MCPAN -e 'install DBIx::DBO2'

If this module has not yet been posted to your local CPAN mirror, you may also retrieve the current distribution from the below address and follow the normal "gunzip", "tar xf", "cd", "perl Makefile.PL && make test && sudo make install" procedure or your local equivalent:

  http://www.evoscript.org/DBIx-DBO2/

Getting Started

You may want to take a look at the test.pl and test-lib/ classes included with this distribution for a short example of how to use this framework to create your own classes.

Prerequisites

Requires DBIx::SQLEngine and Class::MakeMethods, both available on CPAN.

Tested Platforms

This release has been tested succesfully on the following platforms:

  5.6.1 on darwin
  5.005_03 on i386-freebsd

VERSION

This is version 0.005 of DBIx::DBO2.

Distribution Summary

This module's summary in the CPAN DSLIP is intended to read:

  Name            DSLIP  Description
  --------------  -----  ---------------------------------------------
  DBIx::
  ::DBO2          bdpOp  Objects mapping to SQL relational structures

Beta Release

Although it based on earlier code that was extensively tested over several years of production use, this code has recently been majorly refactored, and has not yet been sufficiently tested in its new form.

Discussion and Support

There is not currently any offical discussion and support forum for this pacakage.

Further information and support for this module is available at http://www.evoscript.org.

If you have questions or feedback about this module, please feel free to contact the author at the below address.

I would be particularly interested in any suggestions towards improving the documentation, correcting any Perl-version or platform dependencies, as well as general feedback and suggestions.

SEE ALSO

See DBIx::SQLEngine for information about the underlying database interface.

See DBIx::DBO2::Record, DBIx::DBO2::Fields, DBIx::DBO2::Table, and DBIx::DBO2::TableSet for key interfaces.

Similar Modules

Numerous modules on CPAN provide some type of system to map objects to and from SQL databases, including Class::DBI, Alzabo, and Tangram.

See the Poop Group summary at http://poop.sourceforge.net/ for a review of several other CPAN modules which provide a similar RDBMS-to-OO mapping layer.

For comparison purposes, here are some of the questions asked by the Poop Group summary and their answers for this module:

Supported Databases

Currently supports DBD::AnyData, DBD::CSV, DBD::MySQL, and DBD::Pg.

Providing support for other drivers involves creating a DBD-specific subclass of DBIx::SQLEngine (which will be loaded via DBIx::AnyDBD when appropriate), and should only require a limited amount of coding.

SQL Abstraction

This module supports moderately complex selects, inserts, updates, and deletes, based on the DBIx::SQLEngine abstraction layer. It is possible to apply order by and group by clauses to operations, as well as limits.

Inserts with sequences are supported, with DBIX::SQLEngine providing a workaround using its own sequence table logic for DBDs which don't have native sequence/auto_increment equivalents.

Joins are not supported, although it is possible to pass in snippets of SQL to accomplish this, or to provide your own logic in a subclass.

Invalid SQL

The automated SQL generation should produce valid SQL, but if you pass in incorrect information, such as explicitly requesting a column name which does not exist in the database, or if you pass in a SQL snippet as part of a query, there is no way to validate this prior to actually executing the query and receiving an error from the DBMS.

Deferred/Preloaded data retrieval

There is not yet any way to defer the loading of given columns for a select. However, it always possible to easily specify only those columns which are needed at a given point in your code. (Deferred loading of additional columns is expected in an upcomming release.)

Table Relationships

DBIx::DBO2 supports both many-to-one (foreign key) and one-to-many (reverse foreign key) relationships. Support for one-to-many relationships includes your choice of cascading delete, nullify after delete, and restrict delete rules. You can establish relationships between classes regardless of whether their data is actually stored in the same underlying SQL database.

Multiple rows and cursors

DBIx::DBO2 currently returns multiple rows all at once. A RecordSet object similar to a cursor is used by it does not yet handle incremental retrieval. (Support for cursors and automatic iteration with closures is expected in an upcomming release.)

Caching

There is no built in caching support. (Support for LRU caching and ensuring that there is only a single instance of a given object in memory at any time are both expected in an upcomming release.)

Transactions

DBIx::DBO2 does not support transactions. (Basic transactions for DBDs which support them are expected in an upcomming release.)

Auto-generated methods

The included DBIx::DBO2::Fields package can generate a wide variety of methods, including customized accessors for each type of field or relationship. (These currently require explicit declarations, but support for automatic detection of database columns and subsequent method generation is expected in an upcomming release.)

Other

A callback mechanism allows you to specify method names or arbitrary subroutines to be called immediately before or after each record is retrieved, inserted, updated, or deleted. You can add these callbacks to all record classes, to a particular class, or even to a particular object instance.

Documentation

The documentation for this module is still fairly rough, although efforts are continuing to improve this.

License

GPL/Artistic disjunction. The same as Perl itself.

Support

Support for this module is available from the author (simonm@cavalletto.org). (The author is also available for support contracts or consulting engagements.)

Status

Recently released to CPAN after several years of in-house use. Actively developed and supported by the author.

CREDITS AND COPYRIGHT

Developed By

  M. Simon Cavalletto, simonm@cavalletto.org
  Evolution Softworks, www.evoscript.org

Contributors

  Piglet / EJ Evans, piglet@piglet.org
  Eric Schneider, roark@evolution.com
  Chaos / Matthew Sheahan

Copyright 2002 Matthew Simon Cavalletto.

Portions copyright 1997, 1998, 1999, 2000, 2001 Evolution Online Systems, Inc.

License

You may use, modify, and distribute this software under the same terms as Perl.