NAME DBIx::Iterator - Query your database using iterators and save memory VERSION version 0.0.1 SYNOPSIS # Create an iterator for a simple DBI query my $db = DBIx::Iterator->new( DBI->connect('...') ); my $it = $db->query("SELECT id, name FROM person"); while ( my $row = $it->() ) { say $row->{'id'} . ": " . $row->{'name'}; # Do something with $row... } # We have a basic class here that knows nothing about iterators package Person; use Moose; has 'id' => ( is => 'ro', isa => 'Int' ); has 'name' => ( is => 'ro', isa => 'Str' ); sub label { my ($self) = @_; return $self->id . ": " . $self->name; } # Then we have a role that knows how to create instances # from iterators package FromIterator; use Moose::Role; sub new_from_iterator { my ($self, $it) = @_; return sub { my $row = $it->(); return unless defined $row; return $self->new($row); } } # Then we apply the role to the Person class and use # our plain database iterator that produces hashes to # now create Person instances instead. package main; use Moose::util qw(apply_all_roles); my $p = apply_all_roles('Person', 'FromIterator'); my $it = $p->new_from_iterator( $db->query("SELECT * FROM person") ); while ( my $person = $it->() ) { say $person->label; # Do something with $person... } DESCRIPTION Iterators are a nice way to perform operations on large datasets without having to keep all of the data you're working on in memory at the same time. Most people have experience with iterators already from working with filehandles. They are basically iterators hidden behind a somewhat odd syntax. This module gives you the same way of executing database queries. The trivial example at the start of the synopsis is not very different from using "fetchrow_hashref" in DBI directly to retrieve your database rows. But when we look at the second example we can start to see how it allows much cleaner separation of concerns without having to modify the core class (Person) to support iterators or database interaction at all. For more information about iterators and how they can work for you, have a look at chapter 4 in the book Higher-Order Perl mentioned below. It is free to download and highly recommended. METHODS new($dbh) Creates a new iterator factory connected to the specified database handle. dbh Returns the database handle provided to new(). prepare($query) Asks the database engine to parse the query and return a statement object that can be used to execute the query with optional parameters. query($query, @placeholder_values) Executes the query with the optional placeholder values. Returns a code reference you can execute until it is exhausted. If called in list context, it will also return a reference to the statement object itself. The iterator returns exactly what "fetchrow_hashref" in DBI returns. When the iterator is exhausted it will return undef. SEE ALSO * Higher-Order Perl by Mark Jason Dominus, page 163-173 <http://hop.perl.plover.com/> * Iterator SEMANTIC VERSIONING This module uses semantic versioning concepts from <http://semver.org/>. SUPPORT Perldoc You can find documentation for this module with the perldoc command. perldoc DBIx::Iterator Websites The following websites have more information about this module, and may be of help to you. As always, in addition to those websites please use your favorite search engine to discover more resources. * MetaCPAN A modern, open-source CPAN search engine, useful to view POD in HTML format. <http://metacpan.org/release/DBIx-Iterator> * Search CPAN The default CPAN search engine, useful to view POD in HTML format. <http://search.cpan.org/dist/DBIx-Iterator> * RT: CPAN's Bug Tracker The RT ( Request Tracker ) website is the default bug/issue tracking system for CPAN. <http://rt.cpan.org/NoAuth/Bugs.html?Dist=DBIx-Iterator> * AnnoCPAN The AnnoCPAN is a website that allows community annotations of Perl module documentation. <http://annocpan.org/dist/DBIx-Iterator> * CPAN Ratings The CPAN Ratings is a website that allows community ratings and reviews of Perl modules. <http://cpanratings.perl.org/d/DBIx-Iterator> * CPAN Forum The CPAN Forum is a web forum for discussing Perl modules. <http://cpanforum.com/dist/DBIx-Iterator> * CPANTS The CPANTS is a website that analyzes the Kwalitee ( code metrics ) of a distribution. <http://cpants.perl.org/dist/overview/DBIx-Iterator> * CPAN Testers The CPAN Testers is a network of smokers who run automated tests on uploaded CPAN distributions. <http://www.cpantesters.org/distro/D/DBIx-Iterator> * CPAN Testers Matrix The CPAN Testers Matrix is a website that provides a visual overview of the test results for a distribution on various Perls/platforms. <http://matrix.cpantesters.org/?dist=DBIx-Iterator> * CPAN Testers Dependencies The CPAN Testers Dependencies is a website that shows a chart of the test results of all dependencies for a distribution. <http://deps.cpantesters.org/?module=DBIx::Iterator> Bugs / Feature Requests Please report any bugs or feature requests by email to "bug-dbix-iterator at rt.cpan.org", or through the web interface at <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DBIx-Iterator>. You will be automatically notified of any progress on the request by the system. Source Code The code is open to the world, and available for you to hack on. Please feel free to browse it and play with it, or whatever. If you want to contribute patches, please send me a diff or prod me to pull from your repository :) <http://github.com/robinsmidsrod/DBIx-Iterator> git clone git://github.com/robinsmidsrod/DBIx-Iterator.git AUTHOR Robin Smidsrød <robin@smidsrod.no> COPYRIGHT AND LICENSE This software is copyright (c) 2013 by Robin Smidsrød. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.