Add a score_mode to the rescore

[hc]

I started working on adding a score_mode parameter to the rescore query, something like :

{
    "rescore" : {
      "window_size" : 50,
      "query" : {
         "rescore_query" : {
            "match" : {
               "field1" : {
                  "query" : "the quick brown",
                  "type" : "phrase",
                  "slop" : 2
               }
            }
         },
         "query_weight" : 0.7,
         "rescore_query_weight" : 1.2,
         "score_mode" : "multiply"
      }
   }
}

Default is "total", possible values are : avg, max, min, total and multiply.

My use case is for the "multiply", because I want to do something like:

{
   "query" : {
      // lot of complex queries
      // default scoring
   },
   "rescore" : {
      "window_size" : 500,
      "query" : {
         "rescore_query" : {
            "custom_score" : {
              "query" : { "match_all" : { } },
              "script" : "complex_scoring",
              "lang" : "native"
            }
          },
         "query_weight" : 1.0,
         "rescore_query_weight" : 1.2
      }
   }
}

So rather than having to duplicate my complex query in the rescore query, I just multiply the first score with the second one.

What do you think? I will post my code.

[hc]

Here my commit: hc@c37a2b7

[s1monw]

This looks very useful. I will look into this asap... catching up right now after 3 weeks of absence :)

[s1monw]

I added a comment, can you update the PR?

[s1monw]

any news on the PR?

[hc]

I was also in holidays the past weeks :) I will push it later today.

[s1monw]

cool man I will look soon / tomorrow thanks :)

[s1monw]

this looks really good. One minor thing, since those functions are idempotent can we only create one instance for them and keep it around and then do ScoreMode.Min.INSTANCE instead of new ScoreMode.Min()?

PS: I hope you had a good vacation :)

[hc]

You are definitely right, I added a commit: #3360
I will merge in a single commit once everything is ok.

PS: thanks! You too if that's also the reason of your absence :)

[kimchy]

how about making the score functions simply an enum?

[hc]

Do you mean something like:

    private static enum ScoreMode {
        Avg("avg of:"),
        Max("max of:"),
        Min("min of:"),
        Multiply("product of:"),
        Total("sum of:");

        private final String description;

        ScoreMode(String description) {
            this.description = description;
        }
        public float combine(float primary, float secondary) {
            switch (this) {
                case Avg:
                    return (primary + secondary) / 2;
                case Max:
                    return Math.max(primary, secondary);
                case Min:
                    return Math.min(primary, secondary);
                case Multiply:
                    return primary * secondary;
                case Total:
                default:
                    return primary + secondary;
            }
        }
        public String description() {
            return description;
        }
    }

[kimchy]

the combine method can be abstract on the enum, and each actual enum value can implement it, then you won't need the switch statement.

[hc]

Oh thanks I didn't know about that. I pushed the modification.

[s1monw]

@hc looks good can you squash the commits?

[hc]

I updated the PR

[s1monw]

@hc thanks man! would you mind opening an issue on the doc repo to update the features documentation?