mango-query-test.pl

# This query in Mongo works:
db.tweets.find({ 'extracted': { $exists: false } }).count()


# This query in Mango does not return the same results (filter not applied)
my $results = $mango->db( 'fomo' )->collection( 'tweets' )
    ->find( 
        { 
            'extracted' => { '$exists' => 'false' },
        } 
    )->all;

# This query in Mango returns the same (correct) results as the Mongo query
my $results = $mango->db( 'fomo' )->collection( 'tweets' )
    ->find( 
        { 
            'extracted' => { '$nin' => ['1'] },
        } 
    )->all;

my $results = $mango->db( 'fomo' )->collection( 'tweets' )
->find(
{
'$exists' => { 'extracted' => 'false' },
}
)->all;