Function score doesn't require a function and can specify a weight

[astralarya]

As of 1.4, elasticsearch has added a weight parameter to function score functions. Futhermore, function score queries do not require a score function if they have both a filter and a weight.

https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-function-score-query.html

[olivere]

Hi there! Sorry for the delay. I'm currently OOO and will review your PR ASAP. Thanks for working on this.

[olivere]

I'm currently looking into this. If you have the time, maybe we could figure this out together.

I model the Go code after the Java client as I found the documentation misleading or incomplete sometimes (it probably has to). In other words: The Java code is the gold standard for me. Here's the code that implements the Function score feature in Java. Important classes are FunctionScoreQueryBuilder which basically is FunctionScoreQuery in Elastic and ScoreFunctionBuilders which is what you find in search_queries_fsq_score_funcs.go.

However, when comparing the Java code with your implementation, I see that in Java the weights are only applied to the score functions whereas in your PR you add them to the FunctionScoreQuery. Do we agree that it is the correct thing to add them to the score functions?

BTW: I already have a patch available here (if we agree). So no need to change your PR. It fixes some other issues as well (like the min_score field that came with 1.5.0+, deprecation of FactorFunction and addition of WeightFactorFunction).

[olivere]

Closed this for now. Feel free to open a new issue if this doesn't work for you. Cheers.