Question

In my database I have documents which all contain the property foo. For each value of foo I have a function that either returns true or false. How can I query for all the documents for which the value of foo makes the function return true?

Answer 1

If you need to check if your string field’s value is one of several, you need the $in modifier.

db.collection.find( { field : { $in : array } } );

It works fast and uses index (if possible).

If your field is an array and you pass a string, use this syntax.

db.collection.find({array_field : string_value});

It will check every element in the array and, if any of them matches your string, it will return the document.