How to get data on mongodb via logical query into node.js?

Question

I want to get chat histories on mongodb.So I need use logical query in mongodb.
I have a message object.And Message have to,sender and message.

For example; in mongodb:

-->to: A sender: B message: blabla
-->to: B sender: A message: blahblah
-->to: C sender: A message: haha

I need only speech between A and B limit last 20.How can I do that in node.js?

My code:

function getLastMessageFor(to,sender){
  MongoClient.connect('mongodb://127.0.0.1:27017/mydb', function(err, db) {
    if (err)
      throw err;
    console.log("Connected to Database");

    db.collection('test').find($or :[ $and[{"to":to},{"sender":sender}], $and[{"to":sender},{"sender":to}]]).limit(..){})
  });
}

To me, ı need {(to = toName AND sender = senderName) OR (to = senderName AND sender = toName)}.last(20) the logic of this. But how can I do that in mongodb into nodejs. I need speech between A and B last 20.

Im sorry,copy paste problem.I have written dirty code so I didn't try yet.if you understand this logic,can you write 'find()' codes completely to here? — erginduran
– erginduran, Commented Aug 29, 2014 at 19:09

JohnnyHK · Accepted Answer · 2014-08-29 19:19:37Z

1

It seems you're very close, just clean it up a bit to be:

db.collection('test').find({$or: [
    {"to": to, "sender": sender},
    {"to": sender, "sender": to}
]}).limit(20).toArray(function(err, messages) {
    console.log(messages);
});

There's an implicit $and among fields in the same query object.

answered Aug 29, 2014 at 19:19

JohnnyHK

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