Incorrect pagination https://api.spotify.com/v1/users/{user_id}/playlists

[perminovsi]

Plan

Premium

Country

Canada

Device

REST API

My Question or Issue

Hi everyone!

I ran into a weird issue with paginating over users playlists. Steps to reproduce are:

1. Request some number of users playlists with no offset: ?limit=5&offset=0
2. Request same amount of playlists for the "next page", i.e. offset of the second request is equal limit of the first one: ?limit=5&offset=5

Expected result: in total, 10 unique playlists are returned.

Actual result:in total, 9 unique playlists are returned.

Since third page it works as expected, i.e. two requests with ?limit=5&offset=5 and ?limit=5&offset=10 return non-intersecting lists of items.

Below is a python snippet for reproducing.

import requests
token = '...'

user_id = 'ht1j0ynnwu4hdgfw6g7a0y1nx'

response1 = requests.request(
    method='GET',
    url=f'https://api.spotify.com/v1/users/{user_id}/playlists',
    params={'limit': 5, 'offset': 0},
    headers={'Authorization': f'Bearer {token}'},
)
items1 = [(p['id']) for p in response1.json()['items']]

response2 = requests.request(
    method='GET',
    url=f'https://api.spotify.com/v1/users/{user_id}/playlists',
    params={'limit': 5, 'offset': 5},
    headers={'Authorization': f'Bearer {token}'},
)
items2 = [(p['id']) for p in response2.json()['items']]

print(items1)
print(items2)

It prints:

['6kL8wAlMOYicjD4WE5h5UY', '0L5Ub41BC6UPiOR2i99XDE', '37i9dQZEVXcGu90ywFf8Id', '37i9dQZEVXbmu9hXKCIN5q', '4uJLFAfVHXIGUWIRj95BZ5']
['4uJLFAfVHXIGUWIRj95BZ5', '6NQkzRDINJC25OefUAz8g3', '4jLfWUF6JBVwaieOu8er6K', '1VER2y1u7Q3ymjNscEQoXc', '0VC4kqlB1SdoJsihGG2Vya']

The last item of the first list is equal to the first item of the second list: 4uJLFAfVHXIGUWIRj95BZ5.

Since next page it start working nornally:

response3 = requests.request(
    method='GET',
    url=f'https://api.spotify.com/v1/users/{user_id}/playlists',
    params={'limit': 5, 'offset': 10},
    headers={'Authorization': f'Bearer {token}'},
)
items3 = [(p['id']) for p in response3.json()['items']]

print(items3)

 prints

['1lm98dZ23rv7bFlOkTj5yV', '37EgzYlwQVFPKUUrKTcDvq', '7fSyMpbKv4gH4pJV04JjcJ', '6sGesrjKWbNTVN3YNMJlXl', '2QzAr27YvIQOyB72lySjzW']

 which is correct since it doesn't share items with previous pages.

What is also strange is that this "overlapping" depends on limit. For instance, for limit=3:

['6kL8wAlMOYicjD4WE5h5UY', '0L5Ub41BC6UPiOR2i99XDE', '37i9dQZEVXcGu90ywFf8Id']
['37i9dQZEVXbmu9hXKCIN5q', '4uJLFAfVHXIGUWIRj95BZ5', '6NQkzRDINJC25OefUAz8g3']
['6NQkzRDINJC25OefUAz8g3', '4jLfWUF6JBVwaieOu8er6K', '1VER2y1u7Q3ymjNscEQoXc']

overlapping happens for 2nd and 3rd pages: 6NQkzRDINJC25OefUAz8g3.

Same for limit=4. But since limit=5 overlapping happens between 1st and 2nd pages.

Let me know what you think about it, and please do let me know if any extra information is required!