MongoDB: $all with empty array...

Question

I'm running a query on a collection with documents like these.

{"name": "Daniel", "tags": ["person", "owner", "father"]},
{"name": "Jane", "tags": ["person", "owner", "mother"]},
{"name": "Jimmy", "tags": ["person", "owner", "son"]}

Now, if I want to find all documents matching the tags person AND owner I would do something like this

var match = ['person', 'owner'];
model.find({'tags': {$all: match}});

Now I need to do the following:

When match has values, return all document matching those (This is done)
When match is empty [ ], return all documents.

What's the most efficient way to do that in a single query?

Thanks in advance,

D

BatScream · Accepted Answer · 2015-04-24 20:20:57Z

2

I would suggest you to add the condition in your application layer, and keep your query that gets executed on the server very simple.

If the match array has one or more elements, add a query field to your query condition, else execute an empty condition which would return you all the documents.

snippet:

var match = ['person', 'owner'];
var condition = {};
if(match.length > 0){
   condition["tags"] = {$all:match};
}
db.model.find(condition);

Having said this, with the $all operator, it is not possible to achieve both the conditions in a single query.

The $all operator selects the documents where the value of a field is an array that contains all the specified elements.

edited Apr 24, 2015 at 20:20

answered Apr 24, 2015 at 20:15

BatScream

19.7k4 gold badges54 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Myk Willis Over a year ago

It is surprising that model.find({'tags': {$all: []}}) does not return all documents (assuming tags exists as an empty array in each document).

Collectives™ on Stack Overflow

MongoDB: $all with empty array...

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related