Perl mongodb检查是否存在

Question

what is the fastest way in perl to check if the document in mongodb exists?

Is there any faster way than this?:

my $cursor = $cache->find( { "key" => $key->key } );

if ( $cursor->count ) {
return 1;
}

Answer 1

Using the count method is fine. To save a bit of code, you might use find_one instead:

return 1 if $cache->find_one( { "key" => $key->key } );

Both of these have about the same amount of network overhead, requiring at least two roundtrips to send the query and retrieve the results from the cursor.

You might save yourself a little processing time if you use a command instead. (Under the hood this just does a find_one against the $cmd collection, though.)

my $results = $cache->aggregate( [ { '$match' => { key => $cache->key } }, { '$limit' => 1 } ] );
return 1 if @$results;

But I doubt this level of network overhead will make much of a difference. I encourage you to benchmark it under realistic conditions and see what works best.