ranker.go

package hlquery

import (
    "math"
)

var defaultRankWeights = map[string]float64{
    "popularity_log":  1.15,
    "hit_log":         0.95,
    "popularity_sqrt": 0.25,
    "hit_log_sqrt":    0.15,
}

func ComputeRankSignal(popularity, hitLog float64, weights map[string]float64) float64 {
    w := make(map[string]float64)
    for k, v := range defaultRankWeights {
        w[k] = v
    }

    for k, v := range weights {
        if _, ok := w[k]; ok {
            w[k] = v
        }
    }

    return math.Log(popularity+1)*w["popularity_log"] + math.Log(hitLog+1)*w["hit_log"] + math.Sqrt(popularity)*w["popularity_sqrt"] + math.Sqrt(hitLog)*w["hit_log_sqrt"]
}

func AttachRankSort(params map[string]interface{}, field, direction string) {
    if params == nil {
        return
    }

    dir := direction
    if dir != "asc" && dir != "desc" {
        dir = "desc"
    }

    sortInstruction := field + ":" + dir
    current, ok := params["sort_by"].(string)
    if ok && current != "" {
        params["sort_by"] = current + "," + sortInstruction
    } else {
        params["sort_by"] = sortInstruction
    }
}