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Manual Reference Pages  -  DBIX::CLASS::HELPER::RESULTSET::RANDOM (3)

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NAME

DBIx::Class::Helper::ResultSet::Random - Get random rows from a ResultSet

CONTENTS

SYNOPSIS



 # note that this is normally a component for a ResultSet
 package MySchema::ResultSet::Bar;

 use strict;
 use warnings;

 use parent DBIx::Class::ResultSet;

 __PACKAGE__->load_components(Helper::ResultSet::Random);

 # in code using resultset:
 my $random_row  = $schema->resultset(Bar)->rand->single;



DESCRIPTION

This component allows convenient selection of random rows. See NOTE in DBIx::Class::Helper::ResultSet for a nice way to apply it to your entire schema.

Currently this works by doing something akin to



 SELECT TOP($x) from $table ORDER BY RANDOM()



Lots of people think this is slow. My own benchmarks show that doing the above, for 10 rows in a table with just over 8 million rows, is nearly instant. Although that was with SQL Server, and different databases will handle that differently.

So please, if you have performance issues and want this to work with your database, get in touch and I will do what I can to get it to work quickly enough to suite your needs.

METHODS

    rand

This method takes a single argument, being the size of the random ResultSet to return. It defaults to 1. This Component will throw exceptions if the argument is not an integer or not greater than zero.

    _rand_order_by

This module currently does an ORDER BY on some db specific function. If for some reason it guesses incorrectly for your database the easiest way to fix that in the short-term (ie without patching upstream) is to override this method. So for example, if your db uses RAND() instead of RANDOM() and it’s not in the predefined list of dbs you could just do the following in your ResultSet class:



 sub _rand_order_by { RAND() }



AUTHOR

Arthur Axel fREW Schmidt <frioux+cpan@gmail.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2015 by Arthur Axel fREW Schmidt.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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perl v5.20.3 DBIX::CLASS::HELPER::RESULTSET::RANDOM (3) 2015-11-07

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