elasticsearch - Elasticsearch更改相似性不起作用

Question

更改索引的相似性算法无效。我不想比较BM25与TF-IDF，但是我总是得到相同的结果。我正在使用Elasticsearch5.x。

我已经尝试了一切。将属性的相似性设置为classic或BM25或不进行任何设置

"properties": {
           "content": {
              "type": "text",
              "similarity": "classic"
           },

我还尝试在 settings中设置索引的默认相似度，并在 properties中使用它

"settings": {
     "index": {
        "number_of_shards": "5",
        "provided_name": "test",
        "similarity": {
           "default": {
              "type": "classic"
           }
        },
        "creation_date": "1493748517301",
        "number_of_replicas": "1",
        "uuid": "sNuWcT4AT82MKsfAB9JcXQ",
        "version": {
           "created": "5020299"
        }
     }

我正在测试的查询看起来像这样:

{
  "query": {
    "match": {
      "content": "some search query"
    }
  }
}

Answer 1

我在下面创建了一个示例:

DELETE test
PUT test
{
  "mappings": {
    "book": {
      "properties": {
        "content": {
          "type": "text",
          "similarity": "BM25"
        },
        "subject": {
          "type": "text",
          "similarity": "classic"
        }
      }
    }
  }
}

POST test/book/1
{
  "subject": "A neutron star is the collapsed core of a large (10–29 solar masses) star. Neutron stars are the smallest and densest stars known to exist.[1] Though neutron stars typically have a radius on the order of 10 km, they can have masses of about twice that of the Sun.",
  "content": "A neutron star is the collapsed core of a large (10–29 solar masses) star. Neutron stars are the smallest and densest stars known to exist.[1] Though neutron stars typically have a radius on the order of 10 km, they can have masses of about twice that of the Sun."
}
POST test/book/2
{
  "subject": "A quark star is a hypothetical type of compact exotic star composed of quark matter, where extremely high temperature and pressure forces nuclear particles to dissolve into a continuous phase consisting of free quarks. These are ultra-dense phases of degenerate matter theorized to form inside neutron stars exceeding a predicted internal pressure needed for quark degeneracy.",
  "content": "A quark star is a hypothetical type of compact exotic star composed of quark matter, where extremely high temperature and pressure forces nuclear particles to dissolve into a continuous phase consisting of free quarks. These are ultra-dense phases of degenerate matter theorized to form inside neutron stars exceeding a predicted internal pressure needed for quark degeneracy."
}

GET test/_search?explain
{
  "query": {
    "match": {
      "subject": "neutron"
    }
  }
}
GET test/_search?explain
{
  "query": {
    "match": {
      "content": "neutron"
    }
  }
}

subject和 content字段的相似性定义不同，但是在我提供的两个文档(来自Wikipedia)中，它们具有相同的文本。运行两个查询，您将在解释中看到类似以下内容，并且在结果中得到不同的分数:

第一个查询的

:"description": "idf, computed as log((docCount+1)/(docFreq+1)) + 1 from:"

从第二个开始的

:"description": "idf, computed as log(1 + (docCount - docFreq + 0.5) / (docFreq + 0.5)) from:",