繼上一篇的內容，今天就來實際操作看看吧

先從調整得分的方式開始
我們用以下搜尋出來的文檔當作範例

  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 0.2876821,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }

weight

query：

{
  "query": {
    "function_score": {
      "query": {
        "bool": {
          "must": {
            "match": {
              "student.name": "風間"
            }
          }
        }
      },
      "functions": [
        {
          "filter": {
            "term": {
              "student.name": "風間"
            }
          },
          "weight": 2
        }
      ]
    }
  }
}

結果：

{
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 0.5753642,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }

可以觀察到符合student.name=風間的文檔score乘上了weight變成了2倍

衰減函數

可調參數：
1.origin:中心點，當指定字段的值等於基準，score等於原本的score
2.offest:以origin為中心，為他設置一個偏移量offset給定一個範圍，在此範圍內所有的score也都是和origin一樣為原本的score，不指定預設為0
3.scale:衰減率，即是一個文檔指定字段的值從origin下落時，score改變的速度
4.decay:從origin衰減到scale時所得的score，預設為0.5

基準為age=18的query:

{
  "query": {
    "function_score": {
      "query": {
        "bool": {
          "must": {
            "match": {
              "student.name": "風間"
            }
          }
        }
      },
      "functions": [
        {
          "gauss": {
              "student.age": {
                  ""
                  "origin": "18",
                  "scale": "5",
                  "decay": "0.2"
              }
          }
        }
      ]
    }
  }
}

結果：

{
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 0.2876821,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }

跟原本的沒什麼差別

接下來把origin調整成20
結果：

{
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 0.22237073,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }

可以看到score衰減了一點點

field_value_factor

可調參數：
field：要乘上的字段

query：

{
  "query": {
    "function_score": {
      "query": {
        "bool": {
          "must": {
            "term": {
              "student.name": "風間"
            }
          }
        }
      },
      "functions": [
        {
          "field_value_factor": {
            "field": "student.age"
          }
        }
      ]
    }
  }
}

結果：

{
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 5.1782775,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }

可以看到原本的score乘上了age(*18)變成了5.178...

random_score

random_score加強函數除了能隨機得到一個0~1 的分數，也會使用一個seed 值，來保障生成隨機的順序，當seed 值相同時，生成的隨機結果是一致的
另外從7.0開始需要提供一個字段，該字段可以為生成的隨機種子增加唯一性，不指定默認為id

原文檔

[
  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "-8Xz3nQBXV0k7ep9qP8G",
    "_score" : 0.6931471,
    "_source" : {
      "student" : {
        "sid" : "s1090101",
        "name" : "王小明",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  },
  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 0.2876821,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  },
  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_sXz3nQBXV0k7ep9qP8G",
    "_score" : 0.2876821,
    "_source" : {
      "student" : {
        "sid" : "s1090104",
        "name" : "小新",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }
]

query

{
  "query": {
    "function_score": {
      "query": {
        "bool": {
          "must": {
            "term": {
              "student.class": "資工一1"
            }
          }
        }
      },
      "functions": [
        {
          "random_score": {
            "seed": 100,
            "field": "student.name"
          }
        }
      ]
    }
  }
}

結果

[
  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "-8Xz3nQBXV0k7ep9qP8G",
    "_score" : 0.6600295,
    "_source" : {
      "student" : {
        "sid" : "s1090101",
        "name" : "王小明",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  },
  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_cXz3nQBXV0k7ep9qP8G",
    "_score" : 0.24322112,
    "_source" : {
      "student" : {
        "sid" : "s1090103",
        "name" : "風間",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  },
  {
    "_index" : "school_members",
    "_type" : "_doc",
    "_id" : "_sXz3nQBXV0k7ep9qP8G",
    "_score" : 0.083241574,
    "_source" : {
      "student" : {
        "sid" : "s1090104",
        "name" : "小新",
        "age" : 18,
        "class" : "資工一1"
      }
    }
  }
]

可以看到順序沒變但score全都變了
今天的文章就到這邊，剩下的範例就留給明天吧