Apache AGE - How to use LIMIT to return a random number of rows?

Question

I'm trying to use the LIMIT clause in Apache AGE to return a random number of rows from my graph database. Specifically, I want to return one to three rows at random, instead of a fixed number. I've tried using the toInteger(3 * rand()) + 1 expression in my query, but it's not working as expected. Can someone provide an example of how to use LIMIT to return a random number of rows in Apache AGE?

Answer 1

This query will return 1 to 3 columns:

SELECT * FROM cypher('demo', $$
  UNWIND [1, 2, 3, 4, 5] AS n
  RETURN n
  LIMIT toInteger(3 * rand()) + 1
$$) AS (result agtype);

Here, you can find more information to read.

LIMIT

Answer 2

Keep in mind as per Docs, the rand() function generates a floating number on a approx. uniform distribution. So assuming you have a floating number of 0.38.... from the random function, as per your attempt.

It should come out to 1.14.. to integer -> 1.

Essentially your randomizing function can often generate the same number causing your function to fail to be truly random.

Use the following function to configure your randomizing digit.

SELECT *
FROM cypher('graph_name', $$
     RETURN toInteger((10 * rand()) + 1)
$$) as (randomizer agtype);

For a 3 base a better approach is ->

toInteger((10 * (rand() + 0.13) + rand()) % 3 + 1)

The more random your randomizer is the better your chance of different results on each iteration/call.

EDIT: if you are doing this iteratively, perhaps you can add a variable that can be included in the randomizer.