How to properly update an ArangoDB document with unique index field?

Question

I have the following schema for users table:

   name: string
   emails: [string] // unique index

The index is created in the following way (in go language):

usersCollection.EnsureHashIndex(
    ctx, 
    []string{"emails[*]"}, 
    driver.EnsureHashIndexOptions{Unique: true, Sparse: true})

Let's say I have the following user in the DB:

{_key: "1", name: "A", emails: ["aa@aa.aa"]}

Adding an email using the following command in arangosh returns an error:

> db.users.update("1", {emails: ["aa@aa.aa", "aa2@aa.aa"]})
JavaScript exception in file '/usr/share/arangodb3/js/client/modules/@arangodb/arangosh.js' at 99,7: ArangoError 1210: unique constraint violated - in index 442818 of type rocksdb-hash over ["emails[*]"]; conflicting key: 1

Using replace returns similar error.

How can I properly add an email to the given user?

Answer 1

I'm demonstrating this in arangosh. Creating the collection:

db._create('usersCollection')
[ArangoCollection 497, "usersCollection" (type document, status loaded)]

Add the unique index to the collection:

db.usersCollection.ensureIndex({ type: "hash", fields: [ "emails[*]" ], unique: true, sparse: true })
{ 
  "deduplicate" : true, 
  "fields" : [ 
    "emails[*]" 
  ], 
  "id" : "usersCollection/517", 
  "isNewlyCreated" : true, 
  "selectivityEstimate" : 1, 
  "sparse" : true, 
  "type" : "hash", 
  "unique" : true, 
  "code" : 201 
}

Create the entry as you did:

 db.usersCollection.save({_key: "1", name: "A", emails: ["aa@aa.aa"]})
{ 
  "_id" : "usersCollection/1", 
  "_key" : "1", 
  "_rev" : "_YSk15je---" 
}

Now we use AQL to update the emails field to add the other email:

db._query(`UPDATE '1' WITH {emails: ["aa@aa.aa", "bb@bb.bb"]} IN usersCollection`)
[object ArangoQueryCursor, count: 0, cached: false, hasMore: false]

Inspecting the reply:

db.usersCollection.toArray()
[ 
  { 
    "_key" : "1", 
    "_id" : "usersCollection/1", 
    "_rev" : "_YSk2J1K--_", 
    "name" : "A", 
    "emails" : [ 
      "aa@aa.aa", 
      "bb@bb.bb" 
    ] 
  } 
]

Answer 2

Apparently this is a bug in ArangoDB and will be solved later on:

https://github.com/arangodb/arangodb/issues/8359