OpenSearch top k parameter fix

[dev2049]

For most queries it's the size parameter that determines final number of documents to return. Since our abstractions refer to this as k, set this to be k everywhere instead of expecting a separate param. Would be great to have someone more familiar with OpenSearch validate that this is reasonable (e.g. that having size and what OpenSearch calls k be the same won't lead to any strange behavior). cc @naveentatikonda

Closes #5212

[naveentatikonda]

@dev2049 size and k are different parameters. k is the number of neighbors the search of each graph will return. You must also include the size option, which indicates how many results the query actually returns.

[dev2049]

@dev2049 size and k are different parameters. k is the number of neighbors the search of each graph will return. You must also include the size option, which indicates how many results the query actually returns.

right, but in LangChain k refers to total num docs to return. happy to add an optional knn_top_k parameter as well and pass that in

[naveentatikonda]

@dev2049 size and k are different parameters. k is the number of neighbors the search of each graph will return. You must also include the size option, which indicates how many results the query actually returns.

right, but in LangChain k refers to total num docs to return. happy to add an optional knn_top_k parameter as well and pass that in

People might get confused if we introduce new parameter. I guess that should be fine let's go with what you have already implemented in this PR.