ElasticSearch 查询DSL

查询DSL

在Elasticsearch中，搜索是通过使用基于JSON的查询来进行的。查询由两个子句组成-

叶子查询子句 - 这些子句是匹配项，术语或范围，它们在特定字段中寻找特定值。
复合查询子句 - 这些查询是叶查询子句和其他复合查询的组合，以提取所需的信息。

Elasticsearch支持大量查询。查询以查询关键字开头，然后以JSON对象的形式包含条件和过滤器。下面描述了不同类型的查询。

匹配所有查询

这是最基本的查询；它返回所有内容，每个对象的得分为1.0。


POST /school/_search
{
   "query":{
      "match_all":{}
   }
}

运行上面的代码，我们得到以下结果-


{
   "took" : 7,
   "timed_out" : false,
   "_shards" : {
      "total" : 1,
      "successful" : 1,
      "skipped" : 0,
      "failed" : 0
   },
   "hits" : {
      "total" : {
         "value" : 2,
         "relation" : "eq"
      },
      "max_score" : 1.0,
      "hits" : [
         {
            "_index" : "school",
            "_type" : "school",
            "_id" : "5",
            "_score" : 1.0,
            "_source" : {
               "name" : "Central School",
               "description" : "CBSE Affiliation",
               "street" : "Nagan",
               "city" : "paprola",
               "state" : "HP",
               "zip" : "176115",
               "location" : [
                  31.8955385,
                  76.8380405
               ],
               "fees" : 2200,
               "tags" : [
                  "Senior Secondary",
                  "beautiful campus"
               ],
               "rating" : "3.3"
            }
         },
         {
            "_index" : "school",
            "_type" : "school",
            "_id" : "4",
            "_score" : 1.0,
            "_source" : {
               "name" : "City Best School",
               "description" : "ICSE",
               "street" : "West End",
               "city" : "Meerut",
               "state" : "UP",
               "zip" : "250002",
               "location" : [
                  28.9926174,
                  77.692485
               ],
               "fees" : 3500,
               "tags" : [
                  "fully computerized"
               ],
               "rating" : "4.5"
            }
         }
      ]
   }
}

全文查询

这些查询用于搜索全文，例如章节或新闻文章。该查询根据与该特定索引或文档相关联的分析器工作。在本节中，我们将讨论全文查询的不同类型。

匹配查询

此查询将文本或短语与一个或多个字段的值匹配。


POST /school*/_search
{
   "query":{
      "match" : {
         "rating":"4.5"
      }
   }
}

运行上面的代码后，我们得到如下所示的响应：


{
   "took" : 44,
   "timed_out" : false,
   "_shards" : {
      "total" : 1,
      "successful" : 1,
      "skipped" : 0,
      "failed" : 0
   },
   "hits" : {
      "total" : {
         "value" : 1,
         "relation" : "eq"
      },
      "max_score" : 0.47000363,
      "hits" : [
         {
            "_index" : "school",
            "_type" : "school",
            "_id" : "4",
            "_score" : 0.47000363,
            "_source" : {
               "name" : "City Best School",
               "description" : "ICSE",
               "street" : "West End",
               "city" : "Meerut",
               "state" : "UP",
               "zip" : "250002",
               "location" : [
                  28.9926174,
                  77.692485
               ],
               "fees" : 3500,
               "tags" : [
                  "fully computerized"
               ],
               "rating" : "4.5"
            }
         }
      ]
   }
}

多个匹配查询

此查询将文本或短语与多个字段匹配。


POST /school*/_search
{
   "query":{
      "multi_match" : {
         "query": "paprola",
         "fields": [ "city", "state" ]
      }
   }
}

运行上面的代码后，我们得到如下所示的响应：


{
   "took" : 12,
   "timed_out" : false,
   "_shards" : {
      "total" : 1,
      "successful" : 1,
      "skipped" : 0,
      "failed" : 0
   },
   "hits" : {
      "total" : {
         "value" : 1,
         "relation" : "eq"
      },
      "max_score" : 0.9808292,
      "hits" : [
         {
            "_index" : "school",
            "_type" : "school",
            "_id" : "5",
            "_score" : 0.9808292,
            "_source" : {
               "name" : "Central School",
               "description" : "CBSE Affiliation",
               "street" : "Nagan",
               "city" : "paprola",
               "state" : "HP",
               "zip" : "176115",
               "location" : [
                  31.8955385,
                  76.8380405
               ],
               "fees" : 2200,
               "tags" : [
                  "Senior Secondary",
                  "beautiful campus"
               ],
               "rating" : "3.3"
            }
         }
      ]
   }
}

查询字符串查询

该查询使用查询解析器和query_string关键字。


POST /school*/_search
{
   "query":{
      "query_string":{
         "query":"beautiful"
      }
   }
}

运行上面的代码后，我们得到如下所示的响应：


{
    "took": 16,
    "timed_out": false,
    "_shards": {
        "total": 1,
        "successful": 1,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": {
            "value": 1,
            "relation": "eq"
        },
        "max_score": 1.1374959,
        "hits": [
            {
                "_index": "school",
                "_type": "_doc",
                "_id": "5",
                "_score": 1.1374959,
                "_source": {
                    "name": "Central School",
                    "description": "CBSE Affiliation",
                    "street": "Nagan",
                    "city": "paprola",
                    "state": "HP",
                    "zip": "176115",
                    "location": [
                        31.8955385,
                        76.8380405
                    ],
                    "fees": 2200,
                    "tags": [
                        "Senior Secondary",
                        "beautiful campus"
                    ],
                    "rating": "3.3"
                }
            }
        ]
    }
}

词级查询

这些查询主要处理结构化数据，例如数字，日期和枚举。


POST /school*/_search
{
   "query":{
      "term":{"zip":"176115"}
   }
}

运行上面的代码后，我们得到如下所示的响应：


……………………………..
hits" : [
   {
      "_index" : "school",
      "_type" : "school",
      "_id" : "5",
      "_score" : 0.9808292,
      "_source" : {
         "name" : "Central School",
         "description" : "CBSE Affiliation",
         "street" : "Nagan",
         "city" : "paprola",
         "state" : "HP",
         "zip" : "176115",
         "location" : [
            31.8955385,
            76.8380405
         ],
      }
   }
]   
…………………………………………..

范围查询

该查询用于查找具有给定值范围之间的值的对象。为此，我们需要使用运算符，例如-

gte - 大于等于
gt - 大于
lte - 小于等于
lt - 小于

例如，观察下面给出的代码-


POST /school*/_search
{
   "query":{
      "range":{
         "rating":{
            "gte":3.5
         }
      }
   }
}

运行上面的代码后，我们得到如下所示的响应：


{
   "took" : 24,
   "timed_out" : false,
   "_shards" : {
      "total" : 1,
      "successful" : 1,
      "skipped" : 0,
      "failed" : 0
   },
   "hits" : {
      "total" : {
         "value" : 1,
         "relation" : "eq"
      },
      "max_score" : 1.0,
      "hits" : [
         {
            "_index" : "school",
            "_type" : "school",
            "_id" : "4",
            "_score" : 1.0,
            "_source" : {
               "name" : "City Best School",
               "description" : "ICSE",
               "street" : "West End",
               "city" : "Meerut",
               "state" : "UP",
               "zip" : "250002",
               "location" : [
                  28.9926174,
                  77.692485
               ],
               "fees" : 3500,
               "tags" : [
                  "fully computerized"
               ],
               "rating" : "4.5"
            }
         }
      ]
   }
}

还存在其他类型的术语级别查询，例如-

存在查询 - 如果某个字段具有非null值。
缺少查询 - 这与存在查询完全相反，该查询搜索没有特定字段或字段值为空的对象。
通配符或正则表达式查询 - 此查询使用正则表达式在对象中查找模式。

复合查询

这些查询是不同查询的集合，这些查询通过使用布尔运算符（例如and/or，或not）或针对不同的索引或具有函数调用等彼此合并。


POST /school/_search
{
   "query": {
      "bool" : {
         "must" : {
            "term" : { "state" : "Delhi" }
         },
         "filter": {
            "term" : { "fees" : 2200 }
         },
         "minimum_should_match" : 1,
         "boost" : 1.0
      }
   }
}

运行上面的代码后，我们得到如下所示的响应：


{
   "took" : 6,
   "timed_out" : false,
   "_shards" : {
      "total" : 1,
      "successful" : 1,
      "skipped" : 0,
      "failed" : 0
   },
   "hits" : {
      "total" : {
         "value" : 0,
         "relation" : "eq"
      },
      "max_score" : null,
      "hits" : [ ]
   }
}

地理查询

这些查询处理地理位置和地理位置。这些查询有助于找出学校或任何其他地理位置附近的地理对象。您需要使用地理位置数据类型。


PUT /geo_example
{
   "mappings": {
      "properties": {
         "location": {
            "type": "geo_shape"
         }
      }
   }
}

运行上面的代码后，我们得到如下所示的响应：


{  "acknowledged" : true,
   "shards_acknowledged" : true,
   "index" : "geo_example"
}

现在，我们将数据发布到上面创建的索引中。


POST /geo_example/_doc?refresh
{
   "name": "Chapter One, London, UK",
   "location": {
      "type": "point",
      "coordinates": [11.660544, 57.800286]
   }
}

运行上面的代码后，我们得到如下所示的响应：


{
   "took" : 1,
   "timed_out" : false,
   "_shards" : {
      "total" : 1,
      "successful" : 1,
      "skipped" : 0,
      "failed" : 0
   },
   "hits" : {
      "total" : {
         "value" : 2,
         "relation" : "eq"
      },
      "max_score" : 1.0,
      "hits" : [
         "_index" : "geo_example",
         "_type" : "_doc",
         "_id" : "hASWZ2oBbkdGzVfiXHKD",
         "_score" : 1.0,
         "_source" : {
            "name" : "Chapter One, London, UK",
            "location" : {
               "type" : "point",
               "coordinates" : [
                  11.660544,
                  57.800286
               ]
            }
         }
      }
   }