ElasticSearch 7 DSL查询
在ElasticSearch中，搜索是通过基于JSON的查询来实现的。查询由两种子句组成：
叶查询子句：这些子句是匹配、术语或范围，它们在特定字段中查找特定值。
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支持大数据量查询。查询以query关键字开始，然后以JSON对象的形式包含条件和过滤器。不同类型的查询描述如下
Match All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。例如，
POST /schools*/_search
{
"query":{
"match_all":{}
}
}响应
{
"took":1, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":5, "max_score":1.0, "hits":[
{
"_index":"schools", "_type":"school", "_id":"2", "_score":1.0,
"_source":{
"name":"Saint Paul School", "description":"ICSE Affiliation",
"street":"Dawarka", "city":"Delhi", "state":"Delhi",
"zip":"110075", "location":[28.5733056, 77.0122136], "fees":5000,
"tags":["Good Faculty", "Great Sports"], "rating":"4.5"
}
},
{
"_index":"schools_gov", "_type":"school", "_id":"2", "_score":1.0,
"_source":{
"name":"Government School", "description":"State Board Affiliation",
"street":"Hinjewadi", "city":"Pune", "state":"MH", "zip":"411057",
"location":[18.599752, 73.6821995], "fees":500, "tags":["Great Sports"],
"rating":"4"
}
},
{
"_index":"schools", "_type":"school", "_id":"1", "_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":"schools_gov", "_type":"school", "_id":"1", "_score":1.0,
"_source":{
"name":"Model School", "description":"CBSE Affiliation",
"street":"silk city", "city":"Hyderabad", "state":"AP",
"zip":"500030", "location":[17.3903703, 78.4752129], "fees":700,
"tags":["Senior Secondary", "beautiful campus"], "rating":"3"
}
},
{
"_index":"schools", "_type":"school", "_id":"3", "_score":1.0,
"_source":{
"name":"Crescent School", "description":"State Board Affiliation",
"street":"Tonk Road", "city":"Jaipur", "state":"RJ", "zip":"176114",
"location":[26.8535922, 75.7923988], "fees":2500,
"tags":["Well equipped labs"], "rating":"4.5"
}
}
]
}
}全文检索
这些查询用于搜索全文，如章节或新闻文章。该查询根据与特定索引或文档相关联的分析器工作。在本节中，我们将讨论不同类型的全文检索。
Match查询
此查询将文本或短语与一个或多个字段的值相匹配。例如，
POST /schools*/_search
{
"query":{
"match" : {
"city":"pune"
}
}
}响应
{
"took":1, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":1, "max_score":0.30685282, "hits":[{
"_index":"schools_gov", "_type":"school", "_id":"2", "_score":0.30685282,
"_source":{
"name":"Government School", "description":"State Board Afiliation",
"street":"Hinjewadi", "city":"Pune", "state":"MH", "zip":"411057",
"location":[18.599752, 73.6821995], "fees":500,
"tags":["Great Sports"], "rating":"4"
}
}]
}
}multi_match查询
此查询将文本或短语与多个字段匹配。例如，
POST /schools*/_search
{
"query":{
"multi_match" : {
"query": "hyderabad",
"fields": [ "city", "state" ]
}
}
}响应
{
"took":16, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":1, "max_score":0.09415865, "hits":[{
"_index":"schools_gov", "_type":"school", "_id":"1", "_score":0.09415865,
"_source":{
"name":"Model School", " description":"CBSE Affiliation",
"street":"silk city", "city":"Hyderabad", "state":"AP",
"zip":"500030", "location":[17.3903703, 78.4752129], "fees":700,
"tags":["Senior Secondary", "beautiful campus"], "rating":"3"
}
}]
}
}Query String查询
该查询使用查询解析器和query_string关键字。例如，
POST /schools/_search
{
"query":{
"query_string":{
"query":"good faculty"
}
}
}响应
{
"took":16, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":1, "max_score":0.09492774, "hits":[{
"_index":"schools", "_type":"school", "_id":"2", "_score":0.09492774,
"_source":{
"name":"Saint Paul School", "description":"ICSE Affiliation",
"street":"Dawarka", "city":"Delhi", "state":"Delhi",
"zip":"110075", "location":[28.5733056, 77.0122136],
"fees":5000, "tags":["Good Faculty", "Great Sports"],
"rating":"4.5"
}
}]
}
}Term查询
这些查询主要处理数字、日期等结构化数据。例如，
POST /schools/_search
{
"query":{
"term":{"zip":"176115"}
}
}响应
{
"took":1, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":1, "max_score":0.30685282, "hits":[{
"_index":"schools", "_type":"school", "_id":"1", "_score":0.30685282,
"_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"
}
}]
}
}Range查询
该查询用于查找值在值范围之间的对象。为此，我们需要使用如下运算符
gte:大于等于
gt:大于
lte:小于等于
lt:小于
举个例子：
POST /schools*/_search
{
"query":{
"range":{
"rating":{
"gte":3.5
}
}
}
}响应
{
"took":31, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":3, "max_score":1.0, "hits":[
{
"_index":"schools", "_type":"school", "_id":"2", "_score":1.0,
"_source":{
"name":"Saint Paul School", "description":"ICSE Affiliation",
"street":"Dawarka", "city":"Delhi", "state":"Delhi",
"zip":"110075", "location":[28.5733056, 77.0122136], "fees":5000,
"tags":["Good Faculty", "Great Sports"], "rating":"4.5"
}
},
{
"_index":"schools_gov", "_type":"school", "_id":"2", "_score":1.0,
"_source":{
"name":"Government School", "description":"State Board Affiliation",
"street":"Hinjewadi", "city":"Pune", "state":"MH", "zip":"411057",
"location":[18.599752, 73.6821995] "fees":500,
"tags":["Great Sports"], "rating":"4"
}
},
{
"_index":"schools", "_type":"school", "_id":"3", "_score":1.0,
"_source":{
"name":"Crescent School", "description":"State Board Affiliation",
"street":"Tonk Road", "city":"Jaipur", "state":"RJ", "zip":"176114",
"location":[26.8535922, 75.7923988], "fees":2500,
"tags":["Well equipped labs"], "rating":"4.5"
}
}
]
}
}其他类型的term级查询有：
Exists查询：判断某个字段具有非空值。
Missing查询：与Exists查询相反，该查询搜索没有特定字段或字段值为空的对象。
Wildcard or regexp查询：该查询使用正则表达式来查找对象中的模式。
Type query查询：特定类型的文档。例如，
POST /schools*/_search
{
"query":{
"type" : {
"value" : "school"
}
}
}响应
指定索引中存在的所有school JSON对象。
复合查询
这些查询是通过使用布尔运算符(如and、or、not或for不同索引或具有函数调用等)彼此合并的不同查询的集合。例如，
POST /schools*/_search
{
"query":{
"filtered":{
"query":{
"match":{
"state":"UP"
}
},
"filter":{
"range":{
"rating":{
"gte":4.0
}
}
}
}
}
}响应
{
"took":16, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{"total":0, "max_score":null, "hits":[]}
}Joining查询
这些查询用于包含多个映射或文档的情况。有两种类型的joining查询：
嵌套查询
这些查询处理嵌套映射(您将在下一章中了解更多)。
has_child和has_parent查询
这些查询用于检索在查询中匹配的文档的子文档或父文档。例如，
POST /tutorials/_search
{
"query":
{
"has_child" : {
"type" : "article", "query" : {
"match" : {
"Text" : "This is article 1 of chapter 1"
}
}
}
}
}响应
{
"took":21, "timed_out":false, "_shards":{"total":5, "successful":5, "failed":0},
"hits":{
"total":1, "max_score":1.0, "hits":[{
"_index":"tutorials", "_type":"chapter", "_id":"1", "_score":1.0,
"_source":{
"Text":"this is chapter one"
}
}]
}
}地理位置查询
这些查询处理地理位置，这些查询有助于找到指定位置附近的学校或任何其他地点。您需要使用地理点数据类型。例如，
POST /schools*/_search
{
"query":{
"filtered":{
"filter":{
"geo_distance":{
"distance":"100km",
"location":[32.052098, 76.649294]
}
}
}
}
}响应
{
"took":6, "timed_out":false, "_shards":{"total":10, "successful":10, "failed":0},
"hits":{
"total":2, "max_score":1.0, "hits":[
{
"_index":"schools", "_type":"school", "_id":"2", "_score":1.0,
"_source":{
"name":"Saint Paul School", "description":"ICSE Affiliation",
"street":"Dawarka", "city":"Delhi", "state":"Delhi", "zip":"110075",
"location":[28.5733056, 77.0122136], "fees":5000,
"tags":["Good Faculty", "Great Sports"], "rating":"4.5"
}
},
{
"_index":"schools", "_type":"school", "_id":"1", "_score":1.0,
"_source":{
"name":"Central School", "description":"CBSE Affiliation",
"street":"Nagan", "city":"paprola", "state":"HP", "zip":"176115",
"location":[31.8955385, 76.8380405], "fees":2000,
"tags":["Senior Secondary", "beautiful campus"], "rating":"3.5"
}
}
]
}
}注意，如果在执行上述示例时出现异常，请将以下mapping添加到您的索引中。
{
"mappings":{
"school":{
"_all":{
"enabled":true
},
"properties":{
"location":{
"type":"geo_point"
}
}
}
}
}