mongodb: finding the highest numeric value of a column

Question

I have MongoDB collection of documents containing several fields. One of the columns/fields should be numeric only, but some of these fields contain non-numerical (corrupt)

Answer 1

You can use the $type operator with $not in your query to exclude docs where age is a string. In the shell your query would look like:

db.test.find({age: {$not: {$type: 2}}}).sort({age: -1}).limit(1)

Or in PHP from Martti:

$cursor = $collection->find(array('age' => array('$not' => array('$type' => 2))), array('age' => 1));
$cursor->sort(array('price' => -1))->limit(1);