在ArangoDB中随机选择一个文档

Question

Is there a way to randomly return a document from a collection using AQL?

I would like to create a random graph for testing purposes. I have not yet figured out how to select documents at random from the collection.

I was hoping I might be able to do something like this:

db._query('RETURN nodes[RAND(0..LENGTH(nodes))]').toArray()
JavaScript exception in file '/usr/share/arangodb/js/client/modules/org/arangodb/arangosh.js' at 104,11: [ArangoError 1541: invalid number of arguments for function 'RAND()', expected number of arguments: minimum: 0, maximum: 0 (while parsing)]
!    throw new ArangoError(requestResult);

Any thoughts on how to do this?

Answer 1

@yojimbo87 is right.

To select a random document from a collection you can instead do this:

FOR node IN nodes
  SORT RAND()
  LIMIT 1
  RETURN node

Collection objects in the JavaScript layer (arangosh/Foxx) also have a method for that:

var node = db.nodes.any();

Answer 2

据我所知， RAND() AQL函数不接受任何参数并返回0到1之间的伪随机数，这就是为什么你得到关于无效参数数量的错误的原因。