Question

I try to execute this query with perl on a MongoDB database :

$db->$collection->find({"_id" : { "$in" : ["4f520122ecf6171327000137", "4f4f49c09d1bd90728000034"]}});

But it return nothing and it must return two documents. What is wrong with this query ?

Thank you.

Edit : It doesn’t work too :

$db->$collection->find( {_id => "4f520122ecf6171327000137"} );

Answer 1

First, make sure you’re using the correct syntax. Your first example is not valid Perl code, since you’re including a chunk of JSON as the query parameter.

Second, assuming these ID values are MongoDB ObjectID’s, you’ll need to make OID objects in order to differentiate them from ordinary strings. And make sure to use single quotes ('') around $in, otherwise Perl will try to interpolate $in as a variable (which presumably has nothing in it).

So I assume you want to do something like this:

$db->$collection->find( {
    "_id" => { 
        '$in' => [ MongoDB::OID->new( value => "4f520122ecf6171327000137" ), 
                   MongoDB::OID->new( value => "4f4f49c09d1bd90728000034" )
                 ]
             } 
} );

Edit: Additionally, using autoloaded method names to retrieve collections has been deprecated for a while. You’re better off using $db->get_collection( "collection name" )->find( ... )