Perl: DBIx::Class Beginner - Subsetting Relationships and Prefetching - sql

Question

Okay, I'm new to DBIx::Class. I have a one-to-many relationship set up, like so:
User -> has_many -> Addresses
Okay, good. I can do a query, and call it prefetching JOINed tables, like so:
Foo::DBIC->storage->debug(1); # output SQL to STDOUT
my $user = Foo::DBIC->resultset('Users')->search({}, {
prefetch => [ 'addresses' ],
join => [ 'addresses' ],
rows => 1
})->single;
for my $address ($user->addresses->all) {
say $address->zip_code;
}
Two tables, one SQL query (verified via debug). All is well.
Now, however, let's say I want to write an overload method or two in Foo::DBIC::Result::Users that returns a subset of addresses, based on certain criteria. Here's what I've added to the Users class:
sub home_addresses {
my $self = shift;
return $self->search_related('addresses', { address_type => 'home' });
}
sub business_addresses {
my $self = shift;
return $self->search_related('addresses', { address_type => 'business' });
}
I can call these overloads like so, and they work:
for my $address ($user->home_addresses->all) {
say $address->zip_code;
}
However, this ignores the fact that I've prefetched my join, and it performs ADDITIONAL QUERIES (as if I've not prefetched and joined anything).
So, my question is this: how do I define an overload method that returns a subset of a related table, but uses the already prefetched join? (just appending a WHERE clause to the prefetch)...
My problem is that if I have a lot of the overloaded methods returning related table subsets, my query count can blow up; especially if I'm calling them from within a loop.
I have reasons for doing this that are, of course, ugly. My real life schema is a lot, lot, lot messier than Users and Addresses, and I'm trying to abstract away ugly as best I can.
Thanks!

Answer 1

something like this for home_addresses might work:
sub home_addresses {
my $self = shift;
my $addresses = $self->addresses;
my $home_addresses;
while (my $row = $addresses->next()) {
push #$home_addresses, $row if $row->address_type() eq 'home';
}
my $home_rs = $addresses->result_source->resultset;
$home_rs->set_cache( $home_addresses );
$home_rs;
}
Alternatively, if there a lot of address types something like this:
sub addresses_by_type {
my $self = shift;
my $addresses = $self->addresses;
my $type;
my $rs_type;
while (my $row = $addresses->next()) {
push #{$type->{"".$row->address_type}},
$row;
}
for (keys %$type) {
my $new_rs = $addresses->result_source->resultset;
$new_rs->set_cache( $type->{$_} );
$rs_type->{$_} = $new_rs
}
return $rs_type
}
which you could access the 'home' addresses from like this:
while (my $r = $user->next) {
use Data::Dumper;
local $Data::Dumper::Maxdepth = 2;
print $r->username,"\n";
my $d = $r->addresses_by_type();
my $a = $d->{home};
while (defined $a and my $ar = $a->next) {
print $ar->address,"\n";
}
}

Answer 2

Could you try something like this:
sub home_addresses {
my $self = shift;
my $return = [];
my #addresses = $self->addresses->all();
foreach my $row (#addresses) {
push #$return, $row if $row->address_type() eq 'home';
}
return $return;
}