在同义词之前首先获取带有搜索词的文档 [Elastic]答案

【问题标题】：Getting the document with searched term first, before its synonyms [Elastic]在同义词之前首先获取带有搜索词的文档 [Elastic]
【发布时间】：2018-01-04 07:53:54
【问题描述】：

我想我应该用一个例子来解释我的问题：

假设我使用同义词分析器创建了索引，并声明“laptop”、“phone”和“tablet”是可以概括为“mobile”的相似词：

PUT synonym
{
  "settings": {
    "index": {
      "number_of_shards": 3,
      "number_of_replicas": 2,
      "analysis": {
        "analyzer": {
          "synonym": {
            "tokenizer": "whitespace",
            "filter": [
              "synonym"
            ]
          }
        },
        "filter": {
          "synonym": {
            "type": "synonym",
            "synonyms": [
              "phone, tablet, laptop => mobile"
            ]
          }
        }
      }
    }
  },
  "mappings": {
    "synonym" : {
            "properties" : {
                "field1" : { 
                  "type" : "text",
                  "analyzer": "synonym",
                  "search_analyzer": "synonym"
                }
            }
        }
  }
}

现在我正在创建一些文档：

PUT synonym/synonym/1
{
    "field1" : "phone"
}
PUT synonym/synonym/2
{
    "field1" : "tablet"
}
PUT synonym/synonym/3
{
    "field1" : "laptop"
}

现在当我匹配laptop、tablet 或phone 的查询时，结果总是：

{
  "took": 1,
  "timed_out": false,
  "_shards": {
    "total": 3,
    "successful": 3,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 3,
    "max_score": 0.2876821,
    "hits": [
      {
        "_index": "synonym",
        "_type": "synonym",
        "_id": "2",
        "_score": 0.2876821,
        "_source": {
          "field1": "tablet"
        }
      },
      {
        "_index": "synonym",
        "_type": "synonym",
        "_id": "1",
        "_score": 0.18232156,
        "_source": {
          "field1": "phone"
        }
      },
      {
        "_index": "synonym",
        "_type": "synonym",
        "_id": "3",
        "_score": 0.18232156,
        "_source": {
          "field1": "laptop"
        }
      }
    ]
  }
}

你可以看到tablet的分数总是更高，即使我搜索laptop。

我知道那是因为我将它们声明为相似的词。

但是，我试图弄清楚如何查询，以便带有搜索词的文档可以首先出现在结果列表中的相似词之前。

可以通过boosting来完成，但一定有更简单的方法..

【问题讨论】：

标签： elasticsearch search elasticsearch-5 analyzer synonym

【解决方案1】：

Multi-fields 来救你。以两种方式索引 field1，一种使用同义词分析器，另一种使用标准分析器。现在您可以简单地使用 bool-should 查询来为 field1（同义词）和 field1.raw（标准）上的匹配添加分数。所以，你的映射应该是这样的：

PUT synonym
{
  "settings": {
    "index": {
      "number_of_shards": 3,
      "number_of_replicas": 2,
      "analysis": {
        "analyzer": {
          "synonym": {
            "tokenizer": "whitespace",
            "filter": [
              "synonym"
            ]
          }
        },
        "filter": {
          "synonym": {
            "type": "synonym",
            "synonyms": [
              "phone, tablet, laptop => mobile"
            ]
          }
        }
      }
    }
  },
  "mappings": {
    "synonym": {
      "properties": {
        "field1": {
          "type": "text",
          "analyzer": "synonym",
          "search_analyzer": "synonym",
          "fields": {
            "raw": {
              "type": "text",
              "analyzer": "standard"
            }
          }
        }
      }
    }
  }
}

您可以使用以下方式查询：

GET synonyms/_search?search_type=dfs_query_then_fetch
{
  "query": {
    "bool": {
      "should": [
        {
          "match": {
            "field1": "tablet"
          }
        },
        {
          "match": {
            "field1.raw": "tablet"
          }
        }
      ]
    }
  }
}

注意：我用过search_type=dfs_query_then_fetch。由于您在 3 个分片上进行测试并且文档很少，因此您获得的分数不是应有的分数。这是因为频率是按分片计算的。您可以在测试时使用dfs_query_then_fetch，但不鼓励用于生产。见：https://www.elastic.co/blog/understanding-query-then-fetch-vs-dfs-query-then-fetch

【讨论】：