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.IX Title "DBIx::Class::Helper::ResultSet::Random 3pm"
.TH DBIx::Class::Helper::ResultSet::Random 3pm "2018-04-19" "perl v5.26.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
DBIx::Class::Helper::ResultSet::Random \- Get random rows from a ResultSet
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& # note that this is normally a component for a ResultSet
\& package MySchema::ResultSet::Bar;
\&
\& use strict;
\& use warnings;
\&
\& use parent \*(AqDBIx::Class::ResultSet\*(Aq;
\&
\& _\|_PACKAGE_\|_\->load_components(\*(AqHelper::ResultSet::Random\*(Aq);
\&
\& # in code using resultset:
\& my $random_row  = $schema\->resultset(\*(AqBar\*(Aq)\->rand\->single;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This component allows convenient selection of random rows.  See
\&\*(L"\s-1NOTE\*(R"\s0 in DBIx::Class::Helper::ResultSet for a nice way to apply it to your
entire schema.
.PP
Currently this works by doing something akin to
.PP
.Vb 1
\& SELECT TOP($x) from $table ORDER BY RANDOM()
.Ve
.PP
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 \s-1SQL\s0 Server, and different databases will handle that
differently.
.PP
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.
.SH "METHODS"
.IX Header "METHODS"
.SS "rand"
.IX Subsection "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.
.SS "_rand_order_by"
.IX Subsection "_rand_order_by"
This module currently does an \f(CW\*(C`ORDER BY\*(C'\fR 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 \f(CW\*(C`RAND()\*(C'\fR instead of \f(CW\*(C`RANDOM()\*(C'\fR and
it's not in the predefined list of dbs you could just do the following in your
ResultSet class:
.PP
.Vb 1
\& sub _rand_order_by { \*(AqRAND()\*(Aq }
.Ve
.SH "AUTHOR"
.IX Header "AUTHOR"
Arthur Axel \*(L"fREW\*(R" Schmidt <frioux+cpan@gmail.com>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2018 by Arthur Axel \*(L"fREW\*(R" Schmidt.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.