elasticsearch - 对 `search_as_you_type` ngram子字段感到困惑

Question

我正在尝试在Elasticsearch中名为email_address的字段中添加“键入时搜索”功能。我对from the docs的理解是，如果我创建search_as_you_type字段，它应该自动创建为查找部分匹配而优化的ngram子字段。
但是，它似乎没有按照我期望的方式工作，并且我似乎也没有从这种特殊字段类型中获得期望的 yield 。
首先，我创建了一个带有以下内容的索引:

$ curl -s -H 'Content-Type: application/json' -XPUT http://localhost:9200/mytestindex -d '
{
  "mappings": {
    "properties": {
      "email_address": {"type": "search_as_you_type"}
    }
  }
}
'

当我请求新创建的电子邮件字段时，将看到以下内容:

$ curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_mapping/field/email_address | json_pp
{
   "mytestindex" : {
      "mappings" : {
         "email_address" : {
            "full_name" : "email_address",
            "mapping" : {
               "email_address" : {
                  "max_shingle_size" : 3,
                  "type" : "search_as_you_type"
               }
            }
         }
      }
   }
}

最后，我填充了一些示例数据:

$ curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_doc -d '
{"email_address": "sam@example.com"}'

$ curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_doc -d '
{"email_address": "sally@example.com"}'

$ curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_doc -d '
{"email_address": "jane@example.com"}'

$ curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_doc -d '
{"email_address": "samantha@example.com"}'

官方文档建议使用带有以下字段的 bool_prefix multi_match搜索: email_address， email_address._2gram和 email_address._3gram。好奇地尝试子字段，我测试了仅包含子字段的搜索，但无法获得任何结果:

$ curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_search -d '
{
  "query": {
    "multi_match": {
      "query": "sa",
      "type": "bool_prefix",
      "fields": [
        "email_address._2gram",
        "email_address._3gram"
      ]
    }
  }
}
' | json_pp

{
   "hits" : {
      "hits" : [],
      "max_score" : null,
      "total" : {
         "value" : 0,
         "relation" : "eq"
      }
   },
   "took" : 4,
   "_shards" : {
      "skipped" : 0,
      "successful" : 1,
      "total" : 1,
      "failed" : 0
   },
   "timed_out" : false
}

我尝试了各种长度的部分查询( s， sa， sam等)，但我从未得到任何结果。
当我执行相同的搜索但只包括 email_address字段本身时，我得到了所有期望的结果:

curl -s -H 'Content-Type: application/json' http://localhost:9200/mytestindex/_search -d '
{
  "query": {
    "multi_match": {
      "query": "sa",
      "type": "bool_prefix",
      "fields": [
        "email_address"
      ]
    }
  }
}
' | json_pp
{
   "timed_out" : false,
   "hits" : {
      "max_score" : 1,
      "total" : {
         "relation" : "eq",
         "value" : 3
      },
      "hits" : [
         {
            "_index" : "mytestindex",
            "_id" : "gEbkCXUBC6_J-EeLAygM",
            "_score" : 1,
            "_type" : "_doc",
            "_source" : {
               "email_address" : "sam@example.com"
            }
         },
         {
            "_index" : "mytestindex",
            "_source" : {
               "email_address" : "sally@example.com"
            },
            "_score" : 1,
            "_type" : "_doc",
            "_id" : "gUbkCXUBC6_J-EeLWigu"
         },
         {
            "_index" : "mytestindex",
            "_id" : "jUb5CXUBC6_J-EeL1ij1",
            "_type" : "_doc",
            "_score" : 1,
            "_source" : {
               "email_address" : "samantha@example.com"
            }
         }
      ]
   },
   "took" : 2,
   "_shards" : {
      "failed" : 0,
      "skipped" : 0,
      "successful" : 1,
      "total" : 1
   }
}

结果，我不明白 _2gram和 _3gram子字段提供了什么好处。我设置不正确吗？还是我对这些 Realm 的实际目的感到困惑？

Answer 1

The search_as_you_type field type is a text-like field that isoptimized to provide support for queries that serve an as-you-typecompletion use case

添加带有索引数据，映射，搜索查询和搜索结果的工作示例
索引映射:

{
  "mappings": {
    "properties": {
      "title": {
        "type": "search_as_you_type"
      }
    }
  }
}

索引数据:

{"title": "how shingles are actually used"}

分析API
elasticsearch中的默认标记器是“标准标记器”，它使用基于语法的标记化技术
为文本生成的各个标记是

{
  "tokens": [
    {
      "token": "how",
      "start_offset": 0,
      "end_offset": 3,
      "type": "<ALPHANUM>",
      "position": 0
    },
    {
      "token": "shingles",
      "start_offset": 4,
      "end_offset": 12,
      "type": "<ALPHANUM>",
      "position": 1
    },
    {
      "token": "are",
      "start_offset": 13,
      "end_offset": 16,
      "type": "<ALPHANUM>",
      "position": 2
    },
    {
      "token": "actually",
      "start_offset": 17,
      "end_offset": 25,
      "type": "<ALPHANUM>",
      "position": 3
    },
    {
      "token": "used",
      "start_offset": 26,
      "end_offset": 30,
      "type": "<ALPHANUM>",
      "position": 4
    }
  ]
}

产生3个单词的带状疱疹

POST/_analyze

{
  "tokenizer": "standard",
  "filter": [
    {
      "type": "shingle",
      "min_shingle_size": 3,
      "max_shingle_size": 3,
      "output_unigrams":false
    }
  ],
  "text": "how shingles are actually used"
}

生成的 token 为:

{
  "tokens": [
    {
      "token": "how shingles are",
      "start_offset": 0,
      "end_offset": 16,
      "type": "shingle",
      "position": 0
    },
    {
      "token": "shingles are actually",
      "start_offset": 4,
      "end_offset": 25,
      "type": "shingle",
      "position": 1
    },
    {
      "token": "are actually used",
      "start_offset": 13,
      "end_offset": 30,
      "type": "shingle",
      "position": 2
    }
  ]
}

搜索查询:

title._3gram - Wraps the analyzer of my_field with a shingle tokenfilter of shingle size 3

{
  "query": {
    "multi_match": {
      "query": "shingles are actually",
      "type": "bool_prefix",
      "fields": [
        "title._3gram"
      ]
    }
  }
}

搜索结果:

"hits": [
      {
        "_index": "test",
        "_type": "_doc",
        "_id": "1",
        "_score": 1.0,
        "_source": {
          "title": "how shingles are actually used"
        }
      }
    ]

在您的情况下，考虑到 "text": "samantha@example.com"，生成的各个 token 是: samantha和 example.com当创建2个单词的带状疱疹时，生成的标记为:

{
  "tokens": [
    {
      "token": "samantha example.com",
      "start_offset": 0,
      "end_offset": 20,
      "type": "shingle",
      "position": 0
    }
  ]
}

因此，当您使用sa搜索时，它将不匹配，因为不会生成与之相对应的 token 。
在 bool(boolean) 前缀查询中使用多重匹配时(在email_address字段上，由于" type": "bool prefix"而匹配。阅读此内容以了解有关Match bool prefix query的更多信息。
如果要使用 sa查询并获得所有结果，则可以使用 Completion suggestor，甚至可以遍历 UAX URL Email Tokenizer