Added comment to describe the proposed fix in the test

[dbsrgits/DBIx-Class.git] / t / 98rows_prefetch.t

# Test to ensure we get a consistent result set wether or not we use the
# prefetch option in combination rows (LIMIT).
use strict;
use warnings;

use Test::More;
use lib qw(t/lib);
use DBICTest;

plan $@ ? (skip_all => 'needs DBD::SQLite for testing') : (tests => 2);

my $schema = DBICTest->init_schema();
$schema->storage->debug(1);
my $no_prefetch = $schema->resultset('Artist')->search(
	undef,
	{ rows => 3 }
);

my $use_prefetch = $schema->resultset('Artist')->search(
	undef,
	{
		prefetch => 'cds',
		rows     => 3
	}
);

my $no_prefetch_count  = 0;
my $use_prefetch_count = 0;

is($no_prefetch->count, $use_prefetch->count, '$no_prefetch->count == $use_prefetch->count');

# The fix is to, when using prefetch, take the query and put it into a subquery
# joined to the tables we're prefetching from. This might result in the same
# table being joined once in the main subquery and once in the main query. This
# may actually resolve other, unknown edgecase bugs. It is also the right way
# to do prefetching. Optimizations can come later.

TODO: {
	local $TODO = "This is a difficult bug to fix, workaround is not to use prefetch with rows";
	$no_prefetch_count++  while $no_prefetch->next;
	$use_prefetch_count++ while $use_prefetch->next;
	is(
		$no_prefetch_count,
		$use_prefetch_count,
		"manual row count confirms consistency"
		. " (\$no_prefetch_count == $no_prefetch_count, "
		. " \$use_prefetch_count == $use_prefetch_count)"
	);
}