Filtering query results with mongoose on node.js

Question

I'm developing an app with mongoose to access MongoDB.

And what I'm trying to achieve is to make a query and discar some documents by id.

User.find({})
    .where('price').lt(upperLimit)
    ....
    .exec(function(err, users) {
      //
    });

The point is I want to discard some users that I know before doing the query. Any ideas?. I don't want to post-process users collections and filter.

Thanks!

JohnnyHK · Accepted Answer · 2013-03-13 13:23:31Z

3

You can use the $nin operator to exclude an array of _id values:

User.find({})
  .where('price').lt(upperLimit)
  .nin('_id', idsToExclude)
  ....
  .exec(function(err, users) {
    //
  });

answered Mar 13, 2013 at 13:23

JohnnyHK

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2 Comments

christkv Over a year ago

I would suggest not using the $nin operator if possible and rather use the $ne operator as $nin is not capable of using an index (indexes are only inclusive not exclusive) thus forcing a table scan across all documents.

JohnnyHK Over a year ago

@christkv Actually, neither $nin nor $ne use indexes effectively (see here), but as @nutlike noted in his comments, $ne doesn't work in this case. As long as another query term is included first (in this case price) the $nin only needs to scan through the docs with the matching price, not the whole collection.

nutlike · Accepted Answer · 2013-03-13 13:18:01Z

2

You could use the $ne operator:

User.find({"_id":{"$ne":<IdToExclude>}}). …

answered Mar 13, 2013 at 13:18

nutlike

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4 Comments

Javier Manzano Over a year ago

Ok, but if its, an array of objects?

nutlike Over a year ago

For arrays you could use the $all operator. User.find({"ids":{"$ne":{"$all":[<FirstIdToExclude>,<SecondIdToExclude>,…]}}}). …

nutlike Over a year ago

I think JohnnyHK approach is the better one but could you let us know if this one works too?

nutlike Over a year ago

I just checked it myself and it does not seem to work, sorry! Stick to JohnnyHK's answer for arrays.

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