How to create unique items in RethinkDB

Question

How to create unique items in RethinkDB?

In MongoDb I used ensureIndex for this, eg:

userCollection.ensureIndex({email:1},{unique:true},function(err, indexName){

score 20 · Accepted Answer · answered Jul 22 '13 at 13:49

20

RethinkDB does not currently support uniqueness constraints on fields other than the primary key.

You could use an auxiliary table where the unique field is stored as the primary key in order to check for uniqueness in your application explicitly.

answered Jul 22 '13 at 13:49

Daniel Mewes

Thank you very much! Essentially I just like to make one field unique. If I can solve that with the PrimaryKey it's ok for me! – daslicht Jul 22 '13 at 14:34
6

Is this still the best solution? This was posted 3 years ago. – chovy Jun 20 '16 at 06:38
1

@chovy probably, I think they decided to nix unique secondary keys to avoid the kind of gotcha as in MongoDB allowing unique secondary keys but not guaranteeing their uniqueness across shards. – Andy Jul 18 '16 at 19:34

score 0 · Answer 2 · answered Oct 13 '13 at 01:03

0

A relatively easy alternative would be to use a secondary index. Thus not messing with auxiliary tables.

You can than do the check in your application with the get_all method (http://rethinkdb.com/api/#js:selecting_data-get_all).

answered Oct 13 '13 at 01:03

Chris Spiegl

12

The problem is that you cannot do this atomically. I.e. between the time where you check the secondary index and find that the key does not exist, and the time where you actually insert the document, somebody else could insert a document with the same key. – Daniel Mewes Dec 06 '13 at 19:41
This link is broken. I don't mind if it's not gauranteed atomic -- but can you provide example code? – chovy Jun 20 '16 at 07:18

2 Answers2