Elasticsearch - 查询 DSL
在 Elasticsearch 中，搜索是使用基于 JSON 的查询进行的。查询由两个子句组成 −
叶查询子句 − 这些子句是匹配、术语或范围，用于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，用于提取所需信息。
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。下面介绍了不同类型的查询。
匹配所有查询
这是最基本的查询；它返回所有内容，并且每个对象的得分为 1.0。
POST /schools/_search
{
"query":{
"match_all":{}
}
}
运行上述代码，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" : "schools",
"_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" : "schools",
"_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，如章节或新闻文章。此查询根据与特定索引或文档关联的分析器工作。在本节中，我们将讨论不同类型的全文查询。
匹配查询
此查询将文本或短语与一个或多个字段的值进行匹配。
POST /schools*/_search
{
"query":{
"match" : {
"rating":"4.5"
}
}
}
运行上述代码后，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" : "schools",
"_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"
}
}
]
}
}
多匹配查询
此查询与多个字段匹配的文本或短语。
POST /schools*/_search
{
"query":{
"multi_match" : {
"query": "paprola",
"fields": [ "city", "state" ]
}
}
}
运行上述代码后，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" : "schools",
"_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
此查询使用查询解析器和 query_string 关键字。
POST /schools*/_search
{
"query":{
"query_string":{
"query":"beautiful"
}
}
}
运行上述代码后，我们得到如下所示的响应 −
{
"took" : 60,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 1,
"relation" : "eq"
},
………………………………….
术语级查询
这些查询主要处理数字、日期和枚举等结构化数据。
POST /schools*/_search
{
"query":{
"term":{"zip":"176115"}
}
}
运行上述代码后，我们得到如下所示的响应 −
……………………………..
hits" : [
{
"_index" : "schools",
"_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
此查询用于查找具有给定值范围之间的值的对象。为此，我们需要使用诸如 −
之类的运算符- 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 /schools*/_search
{
"query":{
"range":{
"rating":{
"gte":3.5
}
}
}
}
运行上述代码后，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" : "schools",
"_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查询，例如 −
存在查询 − 如果某个字段具有非空值。
缺失查询 − 这与存在查询完全相反，此查询搜索没有特定字段或具有空值的字段的对象。
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
这些查询是通过使用布尔运算符（如 and、or、not 或针对不同索引或具有函数调用等）相互合并的不同查询的集合。
POST /schools/_search
{
"query": {
"bool" : {
"must" : {
"term" : { "state" : "UP" }
},
"filter": {
"term" : { "fees" : "2200" }
},
"minimum_should_match" : 1,
"boost" : 1.0
}
}
}
运行上述代码后，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点。这些查询有助于找出任何位置附近的学校或任何其他地理对象。您需要使用地理点数据类型。
PUT /geo_example
{
"mappings": {
"properties": {
"location": {
"type": "geo_shape"
}
}
}
}
运行上述代码后，我们得到如下所示的响应 −
{ "acknowledged" : true,
"shards_acknowledged" : true,
"index" : "geo_example"
}
现在我们发布上面创建的索引中的数据。
POST /geo_example/_doc?refresh
{
"name": "Chapter One, London, UK",
"location": {
"type": "point",
"coordinates": [11.660544, 57.800286]
}
}
运行上述代码后，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
]
}
}
}
}
