Function array_sample 

pub fn array_sample<Arr: ArrayOrNullableArray + SingleValue, array, n>(
    array: array,
    n: n,
) -> array_sample<Arr, array, n>
where
    array: AsExpression<Arr>,
    n: AsExpression<Integer>,

Available on crate feature postgres_backend only.

Returns an array of n items randomly selected from array. n may not exceed the length of the array.

Example

let vec = vec![1, 2, 3, 4, 5];
let sampled = diesel::select(array_sample::<Array<Integer>, _, _>(vec.clone(), 3))
    .get_result::<Vec<i32>>(connection)?;
assert_eq!(3, sampled.len());
assert!(sampled.iter().all(|x| vec.contains(x)));

let vec: Vec<i32> = Vec::new();
let sampled = diesel::select(array_sample::<Array<Integer>, _, _>(vec, 0))
    .get_result::<Vec<i32>>(connection)?;
assert_eq!(0, sampled.len());

let sampled = diesel::select(array_sample::<Nullable<Array<Integer>>, _, _>(
    None::<Vec<i32>>,
    1,
))
.get_result::<Option<Vec<i32>>>(connection)?;
assert!(sampled.is_none());