Use Mango to search MongoDB by multiple ObjectIDs - perl

Question

How can I find multiple MongoDB documents by their ObjectIDs using Mango in one go. I currently have a non-blocking sub which I'm using to filter out the docs that don't match in a grep statement but was wondering if it's possible to pass the ObjectIDs (maybe an array of instances of Mango::BSON::ObjectID) to the find method?
I also think it's not very efficient this way since big collections will bare a hefty price!
#items;
$self->mango->db->collection('items')->find()->all(sub {
my ($collection, $err, $items) = #_;
return $self->render_exception($err) if $err;
my #oids = $self->req->params->param('ids[]');
foreach my $item (#$items) {
push #items, $item if grep (/$item->{_id}/, #oids);
}
$self->render(json => {items => \#items});
});
This sub is inside one of my Mojolicous controllers which responds to a JSON call.
I'm using the following:
Mojolicous 4.91
Mango 0.24
MongoDB 2.4.9
Thanks in advance.
Update
I have applied Neil's logic and now it works fine.
my #oids = map { Mango::BSON::ObjectID->new($_) } ($self->req->params->param('ids[]'));
print Dumper(#oids),"\n";
$self->mango->db->collection('items')->find({ "_id" => {'$in' => \#oids} })->all(sub {
my ($collection, $err, $items) = #_;
return $self->render_exception($err) if $err;
print Dumper($items),"\n";
$self->render(json => {items => $items});
});
The dumped OIDs are as follows:
$VAR1 = bless( {
'oid' => '52faf6de10d041d196cb545b'
}, 'Mango::BSON::ObjectID' );
$VAR2 = bless( {
'oid' => '5300409310d041d196cb545d'
}, 'Mango::BSON::ObjectID' );
and the found objects will look something like this (depending on your structure):
$VAR1 = [
{
'_id' => bless( {
'oid' => '52faf6de10d041d196cb545b'
}, 'Mango::BSON::ObjectID' ),
'class' => [
'Sport'
],
'make' => '4321',
'year' => 2012
},
{
'_id' => bless( {
'oid' => '5300409310d041d196cb545d'
}, 'Mango::BSON::ObjectID' ),
'class' => [
'Classic'
],
'make' => '1234',
'year' => 2014
}
]

Answer 1

You seem to be looking for the $in operator. So rather than looping all the items to find the ones that match you pass in the _id values sent to your controller within the call to find():
my #oids = $self->req->params->param('ids[]');
$self->mango->db->collection('items')
->find({ "_id" => { '$in' => \#oids } })->all(sub {
my ($collection, $err, $items) = #_;
return $self->render_exception($err) if $err;
$self->render(json => {items => $items});
});
Update
Actually had some time to test this with Mango and managed to get a working case:
{ "_id" : ObjectId("5345faf8a1f97e61848485e8"), "prerequisites" : [ "a" ] }
{ "_id" : ObjectId("5345fafea1f97e61848485e9"), "prerequisites" : [ "a", "b" ] }
{ "_id" : ObjectId("5345fb02a1f97e61848485ea"), "prerequisites" : [ "a", "c" ] }
And then running with the code:
#!/usr/bin/env perl
use Modern::Perl;
use EV;
use AnyEvent;
use Data::Dumper;
use Mango;
use Mango::BSON::ObjectID;
my $mango = Mango->new();
my $cv = AE::cv;
my $col = $mango->db('test')->collection('courses');
my #oids = (
"5345fafea1f97e61848485e9",
"5345fb02a1f97e61848485ea"
);
#oids = map { Mango::BSON::ObjectID->new($_) } #oids;
$col->find({ '_id' => { '$in' => \#oids } })->all( sub {
my ( $cursor, $err, $docs ) = #_;
$cv->send( Dumper( $docs ) );
});
say $cv->recv;
So that actually will select the correct documents from the sample, and it does seem that the ObjectID values need to be passed in that way in order to match.
At least there should be enough there to debug from.