如何使elasticsearch评分考虑字段长度

Question

我创建了一个非常简单的测试索引，由以下5个条目组成：

{    "tags": [        { "topics": "music festival dance techno germany"}    ]}
{    "tags": [        { "topics": "music festival dance techno"}    ]}
{    "tags": [        { "topics": "music festival dance"}    ]}
{    "tags": [        { "topics": "music festival"}    ]}
{    "tags": [        { "topics": "music"}    ]}

然后我执行以下查询：

{
  "query": { 
    "bool": { 
      "should": [
        { "match": { "tags.topics": "music festival"}}
      ]
    }
  }
}

期望在结果中获得以下顺序：

1）“音乐节”

2)《音乐节舞曲》

然而，我得到了以下结果：

{
    "took": 4,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 5,
        "max_score": 0.5753642,
        "hits": [
            {
                "_index": "testindex",
                "_type": "entry",
                "_id": "1",
                "_score": 0.5753642,
                "_source": {
                    "tags": [
                        {
                            "topics": "music festival dance techno germany"
                        }
                    ]
                }
            },
            {
                "_index": "testindex",
                "_type": "entry",
                "_id": "3",
                "_score": 0.5753642,
                "_source": {
                    "tags": [
                        {
                            "topics": "music festival dance"
                        }
                    ]
                }
            },
            {
                "_index": "testindex",
                "_type": "entry",
                "_id": "4",
                "_score": 0.42221835,
                "_source": {
                    "tags": [
                        {
                            "topics": "music festival"
                        }
                    ]
                }
            },
            {
                "_index": "testindex",
                "_type": "entry",
                "_id": "2",
                "_score": 0.32088596,
                "_source": {
                    "tags": [
                        {
                            "topics": "music festival dance techno"
                        }
                    ]
                }
            },
            {
                "_index": "testindex",
                "_type": "entry",
                "_id": "5",
                "_score": 0.2876821,
                "_source": {
                    "tags": [
                        {
                            "topics": "music"
                        }
                    ]
                }
            }
        ]
    }
}

它的顺序似乎完全随机，除了最低分只匹配一个词。

是什么导致了这种情况，我可以改变什么（在映射、索引或搜索过程中）来获得预期的顺序？

注意：对于非完美匹配查询也是如此。搜索“音乐舞蹈”仍然应该产生3个单词条目作为第一个结果，所以使用或增加术语查询似乎是不可能的。

Answer 1

正如我在这个答案中所描述的，评分/相关性在ElasticSearch中并不是最容易的主题。

我试图为你找到解决方案，目前我有这样的东西。

文件：

{ "tags": [ { "topics": ["music", "festival", "dance", "techno", "germany"]} ], "topics_count": 5 }
{ "tags": [ { "topics": ["music", "festival", "dance", "techno"]} ], "topics_count": 4 }
{ "tags": [ { "topics": ["music", "festival", "dance"] } ], "topics_count": 3 }
{ "tags": [ { "topics": ["music", "festival"]} ], "topics_count": 2 }
{ "tags": [ { "topics": ["music"]} ], "topics_count": 1 }

和查询：

{
  "query": {
    "bool": {
      "should": [
        {
          "function_score": {
            "query": {
              "terms_set": {
                "tags.topics" : {
                  "terms" : ["music", "festival"],
                  "minimum_should_match_script": {
                    "source": "params.num_terms"
                  }
                }
              }
            },
            "script_score" : {
              "script" : {
                "source": "_score * Math.sqrt(1.0 / doc['topics_count'].value)"
              }
            }
          }
        },
        {
          "function_score": {
            "query": {
              "terms_set": {
                "tags.topics" : {
                 "terms" : ["music", "festival"],
                 "minimum_should_match_script": {
                    "source": "doc['topics_count'].value"
                  }
                }
              }
            },
            "script_score" : {
              "script" : {
                "source": "_score * Math.sqrt(1.0 / doc['topics_count'].value)"
              }
            }
          }
        }
      ]
    }
  }
}

它并不完美。还需要一些改进。在这个示例中，它对[“music”,“festival”]和[“music”,“dance”]工作得很好（在ES 6.2上进行了测试），但我猜在其他结果中，它不会像您预期的那样100%工作。主要是因为相关性/评分的复杂性。但是你现在可以读到更多关于我使用过的东西，并试图改进它。