Knn Search support

[hkulekci]

Solves #27.

[hkulekci]

Elasticsearch started supporting multiple Knn query with version 8.7. So, to be able to support the versions between 8.7 and 8.4, I just put these if controls. It will return the Knn query itself if the container has just one Knn query. The container has multiple Knn query, it will return an array of Knn queries.

[hkulekci]

KNN support is moved from _knn_search to _search endpoint in version 8.4.0, so for this reason, I change the elasticsearch version of Github CI as 8.4.0. Knn query support will be provided for elasticsearch 8.4.0 and above. :|

[hkulekci]

Ping @alexander-schranz

[alexander-schranz]

I did not have time to have deeper look at it just by your comment in #27. I did see:

$knn->setFilter($matchAll);

If I'm looking at the existing API I would expect here addFilter:

$knn->addFilter($matchAll);

But else I think the params make sense.

[hkulekci]

After giving it some thought, I believe we should stick with setFilter as there is no support for multiple filters for Knn search. Instead, we can set a filter as a bool query. Using addFilter can be misleading as it may give the impression that we can add multiple filters for Knn. However, the filter field of Knn only accepts one query. And enrichment comes with bool query as well.

[hkulekci]

Ping @alexander-schranz

[hkulekci]

Hey @alexander-schranz, could you find a chance to look into this PR? I hope we can find a chance to merge this.

Thanks.

[hkulekci]

@alexander-schranz I've made some additional improvements to implement a solution for KNN and Sparse Vector search as the query. I hope we can find a way to merge this PR into the library.

hkulekci#6

[alexander-schranz]

Released as 8.2.0. Thx @hkulekci

[hkulekci]

Oh, really! Thanks for merging! I need to prepare another PR as a next step. Will ping you again.