How to increment the attribute value

Question

I have a Posts collection in ArangoDb. I have views attribute in it. I want to update it by one when someone view the Post.

How I can increment the views attribute value by one with AQL in ArangoDB.

I have done above with below query in OrientDb.

update posts INCREMENT views = 1 where @rid = '#10:12'

Answer 1

You achieve this in ArangoDB using the UPDATE statement after a FILTER to pick the post you want to modify:

Lets create a collection with some documents:

db._create('posts')
db.posts.save({views: 1, rid: '#10:12'})
db.posts.save({views: 1, rid: '#11:12'})

First we revalidate our FILTER condition:

db._query(`FOR post IN posts FILTER post.rid == '#10:12' RETURN post`).toArray()
[ 
  { 
    "_key" : "1282487", 
    "_id" : "posts/1282487", 
    "_rev" : "1282806", 
    "rid" : "#10:12", 
    "views" : 1 
  } 
]

We check back for arithmetic calculations:

db._query(`FOR post IN posts FILTER post.rid == '#10:12'
             RETURN post.views + 1`).toArray()
[1]

Now we know everything working properly we phrase the update statement:

db._query(`FOR post IN posts FILTER post.rid == '#10:12'
             UPDATE post WITH {views: post.views + 1} IN posts`)
db.posts.toArray()
[ 
  { 
    "_key" : "1282487", 
    "_id" : "posts/1282487", 
    "_rev" : "1282806", 
    "rid" : "#10:12", 
    "views" : 2 
  } 
]