[FEATURE] Implement pagination for Hybrid Search

[martin-gaievski]

Is your feature request related to a problem?

Current implementation of Hybrid search doesn't have support for pagination, meaning all results are returned "at once". That is standard for many queries in OpenSearch and it's expected that Hybrid Search supports it, https://opensearch.org/docs/latest/search-plugins/searching-data/paginate/.

What solution would you like?

It should be possible to define "from" and positions in as part of the Hybrid query, and results should have (from + size) number of records, starting from "from" position. Standard syntax should be fine in this case:

{
   "from": 20,
   "size": 10,
   "query": {
       "hybrid": [
           {},// First Query
           {} // Second Query
           ..... // Other Queries
       ] 
   }
}

What alternatives have you considered?

It's possible to set higher size and then throw first X elements, but that is required extra processing logic on a client size and is not very optimal.

[ankitas3]

When can we expect this in OpenSearch?

[jackh-ncl]

@martin-gaievski @ankitas3 Just double checking, but from and size already seem to be working for me with Hybrid search while using Opensearch 2.11. Has it been implemented since this issue was raised?

[martin-gaievski]

@jackh-ncl it has not been implemented yet. With existing code it may work, but not for every scenario and when it works it does it not in an optimal way.

[jackh-ncl]

Aha thank you for confirming, yeah I have now noticed that I seem to consistently end up with a total hits value of 5 * the size parameter with the query I'm running.

[benmcginnis]

any chance we can get this in 2.14 or the version after that?

[brandon-carag]

Is anyone from opensearch able to provide any broad details around when pagination will be made available?

[qmauret]

+1 for this feature request

[mkerimyilmaz]

@martin-gaievski Can you please clarify why it doesn't work optimally?

@jackh-ncl it has not been implemented yet. With existing code it may work, but not for every scenario and when it works it does it not in an optimal way.

[JPSoteloSilva]

@martin-gaievski Any idea on when this feature will be available? Thanks

[brandon-carag]

Hi @vamshin and @martin-gaievski,

Just to briefly restate the case here, pagination is a critical feature for many users adopting hybrid search. There has been significant community interest in this thread (at least 20 distinct users) that also point to strong user demand.

I'm sure there are several competing dev priorities here, but this seems like a core item that shouldn't fall to the wayside. At the very least, can we get a very rough approximate timeline here? I suspect there are many people on this thread whose downstream roadmaps are reliant on what happens here.

Thanks in advance

[vamshin]

@brandon-carag Thank you for your interest in pagination functionality. We understand the importance of this feature, and it's on our roadmap. However, at the moment, we're focusing our efforts on enhancing the sorting and explain (raw scores for debugging) capabilities.

While we don't have a definite timeline for implementing pagination, we estimate it could be available towards the end of the year. Please note that this is a rough estimate, and the actual timeline may vary depending on our priorities and resource availability.

We're always open to collaboration and would be delighted if someone from the community is willing to contribute to this feature. If you or anyone else is interested in contributing, please feel free to reach out to us. We can provide guidance and support to ensure a smooth integration of the pagination functionality.

As a work around, is it possible to use a "size" parameter with a large value? I think we can get upto 10K results

[brandon-carag]

@vamshin Thanks for the prompt response--that's helpful info, the rough timeline you mentioned is useful to know. I believe martin mentioned above "it has not been implemented yet. With existing code it may work, but not for every scenario and when it works it does it not in an optimal way." I'm not exactly clear on the boundaries where the existing pagination logic breaks down in the existing implementation.

For even a relatively small corpus, it seems like specifying a large size and processing client-side won't scale for even a relatively small index, particularly if OpenSearch is being used to service API requests and apply pagination. As such, hoping this feature can emerge sooner rather than later.

[sonic182]

has anyone tried scroll api as an alternative? it works?

[brandon-carag]

My understanding is that the scroll API won't solve this issue. Documentation states, "Because search contexts consume a lot of memory, we suggest you don’t use the scroll operation for frequent user queries. Instead, use the sort parameter with the search_after parameter to scroll responses for user queries." https://opensearch.org/docs/latest/api-reference/scroll/