Spring-ai TopK parameter not working for values larger than the default (ElasticSearch), only working has a client-side limit

When creating a request for a query using Elasticsearch store

        SearchRequest request = SearchRequest.query(query);
        List<Document> docs = store.similaritySearch(request);

The default query size from ES is 10 results SearchRequest.query(query) => 10 results

If I set a smaller value, eg 5 SearchRequest.query(query)withTopK(5); => 5 results (OK)

If I set a larger value, eg 100 SearchRequest.query(query)withTopK(100); => 10 results (Not OK) I was expecting 100

This happens because the size parameter of the ES SerachRequest (co.elastic.clients.elasticsearch.core.SearchRequest) is never set, the topK is applied only after the query results, which I think is wrong. Doing the query directly on the _search ES rest api, I get the intended response -100 results (although not being a similarity query), eg

{
  "query": {
    "match_all": {}
  },
  "size": 100
}

Changing in debug the value of SearchRequest.size to 100, I can get also the intended result.

Comment From: karol-antczak

I have the same problem. Ended up making custom VectorStore implementation.