[openstack-dev] [keystone] Pagination
jaypipes at gmail.com
Tue Aug 13 21:40:08 UTC 2013
On 08/13/2013 05:04 PM, Gabriel Hurley wrote:
> I have been one of the earliest, loudest, and most consistent PITA's about pagination, so I probably oughta speak up. I would like to state three facts:
> 1. Marker + limit (e.g. forward-only) pagination is horrific for building a user interface.
> 2. Pagination doesn't scale.
> 3. OpenStack's APIs have historically had useless filtering capabilities.
> In a world where pagination is a "must-have" feature we need to have page number + limit pagination in order to build a reasonable UI. Ironically though, I'm in favor of ditching pagination altogether. It's the lowest-common denominator, used because we as a community haven't buckled down and built meaningful ways for our users to get to the data they really want.
> Filtering is great, but it's only 1/3 of the solution. Let me break it down with problems and high level "solutions":
> Problem 1: I know what I want and I need to find it.
> Solution: filtering/search systems.
This is a good place to start. Glance has excellent filtering/search
capabilities -- built in to the API from early on in the Essex
timeframe, and only expanded over the last few releases.
Pagination solutions should build on a solid filtering/search
functionality in the API, where there is a consistent sort key and
direction (either hard-coded or user-determined, doesn't matter).
Limit/offset pagination solutions (forward and backwards paging, random
skip-to-a-page) are inefficient from a SQL query perspective and should
be a last resort, IMO, compared to limit/marker. With some smart
session-storage of a page's markers, backwards paging with limit/marker
APIs is certainly possible -- just store the previous page's marker.
> Problem 2: I don't know what I want, and it may or may not exist.
> Solution: tailored discovery mechanisms.
This should not be a use case that we spend much time on. Frankly, this
use case can be summarized as "the window shopper scenario". Providing a
quality search/filtering mechanism, including the *API* itself providing
REST-ful discovery of the filters and search criteria the API supports,
is way more important...
> Problem 3: I need to know something about *all* the data in my system.
> Solution: reporting systems.
Sure, no disagreement there.
> We've got the better part of none of that.
I disagree. Some of the APIs have support for a good bit of
search/filtering. We just need to bring all the projects up to search
p.s. I very often go to the second and third pages of Google searches.
:) But I never skip to the 127th page of results.
> But I'd like to solve these issues. I have lots of thoughts on all of
those, and I think the UX and design communities can offer a lot in
terms of the usability of the solutions we come up with. Even more, I
think this would be an awesome working group session at the next summit
to talk about nothing other than "how can we get rid of pagination?"
> As a parting thought, what percentage of the time do you click to the second page of results in Google?
> All the best,
> - Gabriel
> OpenStack-dev mailing list
> OpenStack-dev at lists.openstack.org
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