How do I run a filter on a getNearest() query in RethinkDB?

问题

I have a table with users and their locations saved as r.point datatypes & a geo index set on them. I am trying to run a .getNearest() query, which returns all the users closest to the given user (say, Mr. X). The results return all the users closest to Mr. X, but also include Mr. X. How do I filter all users except Mr. X?

What I've tried so far —

In RethinkDB's Data Explorer (Plain ReQL commands)

r.db('myDb').table('myTable').getNearest(r.point(-20, 39), {index: 'location'}).filter(function(user) {return user.id !== '2ff8902e-97f0-431a-a51c-900a57532967'}); // Assuming Mr.X's `id` is `2ff8902e-97f0-431a-a51c-900a57532967`

This returns all users, including Mr. X. Attempt #2 was -

r.db('myDb').table('myTable').getNearest(r.point(-20, 39), {index: 'location', maxDist:9000000}).filter(r.row('id').ne('2ff8902e-97f0-431a-a51c-900a57532967'));

This returns nothing.

In thinky, a Node.js ORM for RethinkDB.

UserModel.getNearest(r.point(-20, 39), {index: 'location'}).filter(function(user) {return user.id !== '2ff8902e-97f0-431a-a51c-900a57532967'}).run();

This returns all users, including Mr. X.

One solution I'm already aware of —

Using Thinky, I can do this.

const userId = '2ff8902e-97f0-431a-a51c-900a57532967';
const location = r.point(-20, 39);
const queryOptions = {index: 'location'};
UserModel.getNearest(location, queryOptions).run().then(function (users) {
  return users.filter(function(user) {
    return user.doc.id !== userId;
  });
});

I have a feeling I can make this faster; by making sure either the .filter() or another alternative function is run on the RethinkDB server than on my end. Is there room for improvement here? Or perhaps a nicer solution that I am overlooking?

回答1:

You actually do it correct and almost there. You just happen to use filter with wrong key.

r.db('myDb').table('myTable').getNearest(r.point(-20, 39), {index: 'location'})
    .filter(function(user) {
           return user('doc')('id').ne('2ff8902e-97f0-431a-a51c-900a57532967')
    })

The key thin is:

getNearest returns an array of document. Each document has two fields: dist and doc(which is the document in table itself). Hence here we are using user('doc')('id') to get the key. https://rethinkdb.com/api/javascript/get_nearest/
Inside filter function, we have to use ReQL command, in this case, the ne mean, not equal. https://www.rethinkdb.com/api/javascript/ne/

This is fast because we have the index on location. And filter function is executed on RethinkDB server.

来源：https://stackoverflow.com/questions/33255750/how-do-i-run-a-filter-on-a-getnearest-query-in-rethinkdb

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javascript

rethinkdb

thinky