DBIx::Class joins generate a large number of select statements - perl

Question

I've noticed that when I do a join in a select in DBIx::Class, I get a ton of SELECT statements as a result. For instance, I have a query that looks like:
my $testSetRs = $db->resultset('Testset')->search(
{%searchCriteria},
{
prefetch => [
{
'ax_group_testsets' => {'ax_group' => 'ax_user_groups'},
},
{'ax_user_testsets' => 'ax_user'},
],
'+columns' => [
{
'me.ax_group_testsets.ax_group_id' => 'ax_group_testsets.ax_group_id',
'me.ax_group_testsets.ax_group.public' => 'ax_group.public',
'me.ax_group_testsets.ax_group.name' => 'ax_group.name',
},
],
collapse => 1,
group_by => ['me.ts_id', 'me.ts_name'],
cache => 1,
}
);
generates:
SELECT me.ts_id, me.ts_name
FROM testset me
LEFT JOIN ax_group_testset ax_group_testsets ON ax_group_testsets.ts_id = me.ts_id
LEFT JOIN ax_group ax_group ON ax_group.ax_group_id = ax_group_testsets.ax_group_id
LEFT JOIN ax_user_group ax_user_groups ON ax_user_groups.ax_group_id = ax_group.ax_group_id
LEFT JOIN ax_user_testset ax_user_testsets ON ax_user_testsets.ts_id = me.ts_id
LEFT JOIN ax_user ax_user ON ax_user.ax_user_id = ax_user_testsets.ax_user_id
WHERE ( ( ax_user.ax_user_id = ? OR ax_user_groups.ax_user_id = ? ) )
GROUP BY me.ts_id, me.ts_name: '349', '349'
SELECT me.ax_group_id, ax_group.public, ax_group.name FROM ax_group_testset me JOIN ax_group ax_group ON ax_group.ax_group_id = me.ax_group_id WHERE ( me.ts_id = ? ): '4476'
SELECT me.ax_group_id, ax_group.public, ax_group.name FROM ax_group_testset me JOIN ax_group ax_group ON ax_group.ax_group_id = me.ax_group_id WHERE ( me.ts_id = ? ): '4566'
SELECT me.ax_group_id, ax_group.public, ax_group.name FROM ax_group_testset me JOIN ax_group ax_group ON ax_group.ax_group_id = me.ax_group_id WHERE ( me.ts_id = ? ): '4701'
etc.
The first SELECT, I want. Its the ones that come after that bother me. There is one for every group (over 40). This happens on all of my joins and can jump into the hundreds with the right query. Why are so many queries generated and what can I do about it?
I'm running Perl ActiveState 5.16 and DBIx .08250.

Answer 1

Your answer lies in the prefetch atribute as described in the DBIx::Class::Manual::Joining and DBIx::Class::ResultSet docs.
Add
prefetch => {'ax_group_testsets' => {'ax_group' => 'ax_user_groups'} },
and, assuming that you want all three related record columns:
'+columns' => [
{
'me.ax_group_testsets.ax_group_id' => 'ax_group_testsets.ax_group_id',
'me.ax_group_testsets.ax_group.public' => 'ax_group.public',
'me.ax_group_testsets.ax_group.name' => 'ax_group.name',
},
],
collapse => 1,
to the query attributes hash.