通过“_id”查找文档时，Id的查询和Term Query有什么区别？答案

【问题标题】：What's the difference between Id's query and Term Query when finding documents by "_id"?通过“_id”查找文档时，Id的查询和Term Query有什么区别？
【发布时间】：2021-07-24 07:02:27
【问题描述】：

我想通过“_id”获取文档，我有3个选择：

GET document by "_id" GET order/_doc/001

Use Id's Query, GET order/_search { "query": { "ids" : { "values" : ["001"] } } } Though Id's query takes array of Id's but I will be using it to get only one document at a time, so just passing one id in "values" : ["001"]

Use Term Query GET order/_search { "query": {"term": {"_id" : "001"}}}

我想知道Id的查询和Term Query有什么区别，性能方面以及我应该注意的任何其他点？

我应该选择哪一个（在 Id's 和 Term Query 之间）？

非常感谢任何帮助:)

【问题讨论】：

标签： elasticsearch elastic-stack

【解决方案1】：

第一个选项不是搜索，只是通过 id 获取文档。

如果您查看第二个和第三个查询的执行计划，您会发现它们是相同的：

ID查询：

GET order/_search
{
  "explain": true, 
  "query": {
    "ids": {
      "values": ["001"]
    }
  }
}

执行计划：

    "_explanation" : {
      "value" : 1.0,
      "description" : "sum of:",
      "details" : [
        {
          "value" : 1.0,
          "description" : "ConstantScore(_id:[fe 0 1f])",
          "details" : [ ]
        },
        {
          "value" : 0.0,
          "description" : "match on required clause, product of:",
          "details" : [
            {
              "value" : 0.0,
              "description" : "# clause",
              "details" : [ ]
            },
            {
              "value" : 1.0,
              "description" : "DocValuesFieldExistsQuery [field=_primary_term]",
              "details" : [ ]
            }
          ]
        }
      ]
    }

词条查询：

GET order/_search
{
  "explain": true, 
  "query": {
    "term": {
      "_id": "001"
    }
  }
}

执行计划：

  "_explanation" : {
      "value" : 1.0,
      "description" : "sum of:",
      "details" : [
        {
          "value" : 1.0,
          "description" : "ConstantScore(_id:[fe 0 1f])",
          "details" : [ ]
        },
        {
          "value" : 0.0,
          "description" : "match on required clause, product of:",
          "details" : [
            {
              "value" : 0.0,
              "description" : "# clause",
              "details" : [ ]
            },
            {
              "value" : 1.0,
              "description" : "DocValuesFieldExistsQuery [field=_primary_term]",
              "details" : [ ]
            }
          ]
        }
      ]
    }

有什么不同吗？没有！

【讨论】：