Question

I am trying to generate a list of elements :

• red
• green
• orange
• blue
• yellow+

In that case orange is selected and I have the two elements before and the two elements after.

How can I get this list from a MySQL query?

An example of a table :

5 – A

---

1 – B

---

4 – C

---

8 – D

---

7 – E

---

9 – F

---

3 – G

Answer 1

I finally did it with an application code :

def get_list_queryset(self):
    STEP = 5
    LIST_SIZE = 2*STEP+1
    current_object = self.get_object()
    query_set = list(self.model.objects.order_by(*self.model._meta.ordering))
    index = query_set.index(current_object)

    # Index too close to start
    if index < STEP:
        start_ind = 0
        end_ind = LIST_SIZE # We don't care if it's too big.
    # Index too close to end
    elif index+STEP >= len(query_set):
        end_ind = len(query_set)
        start_ind = end_ind>=LIST_SIZE and end_ind-LIST_SIZE or 0
    else:
        start_ind = index-STEP
        end_ind = start_ind+LIST_SIZE

    return query_set[start_ind:end_ind]

The answer is that MySQL is not good to handle that, so it is more flexible to do it in the application.