前言
elasticsearch的核心在搜索，搜索的核心在搜索语法，所以今天我们来梳理下elasticsearch的一些搜索语法，今天主要探讨搜索，主要包括两方面的内容，一方面是普通的query，也就是数据的检索，另一方面就是内容的聚合，也就是传统sql中的分组。
好了，下面我们就来看下这两种搜索查询的具体操作吧。
搜索语法
全文搜索
全文搜索的规则是会匹配凡是包括我们检索内容的任一单词，都会将结果予以展示，它并不关系单词顺序。对于下面我们的搜索表达式，它会搜索about中包括go和reading的所有内容。
搜索语法：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query" : {
"match" : {
"about" : "go reading"
}
}
}
'
返回结果：
7{
"took" : 220,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 7,
"relation" : "eq"
},
"max_score" : 0.9161128,
"hits" : [
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "1",
"_score" : 0.9161128,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 15,
"about" : "I love to go reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "6",
"_score" : 0.9161128,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "7",
"_score" : 0.8500352,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading and go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "8",
"_score" : 0.8500352,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go and reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "5",
"_score" : 0.6706225,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "2",
"_score" : 0.2761543,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to climbing go rock",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "3",
"_score" : 0.2761543,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
}
]
}
}
从结果中，我们可以看到，go reading和reading go这样的内容都被匹配到了，同时他们的匹配度都是相同的，当然他们也是匹配度最高的。而且检索内容还匹配到了包含go和reading的内容，但是包含reading匹配项的匹配度比包含go匹配项的匹配度要高。
目前还不清楚它这个匹配度是如何计算的，现在只要知道_score越高，表示匹配度越高就行了。
短语搜索
相比于全文搜索，短语搜索属于更精确的搜索。我们前面刚说过，全文搜索会将内容拆分之后进行搜索，属于更模糊的搜索，但是短语搜索必须匹配到完整的短语才算。所以对于下面的检索语句，它只会匹配包含go reading的内容：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query" : {
"match_phrase" : {
"about" : "go reading"
}
}
}
'
返回结果：
{
"took" : 5,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 1,
"relation" : "eq"
},
"max_score" : 1.1097687,
"hits" : [
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "1",
"_score" : 1.1097687,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 15,
"about" : "I love to go reading",
"interests" : [
"sports",
"music"
]
}
}
]
}
}
从结果我们可以看出来，最终结果只匹配到了包括go reading这个短语的内容，包含其中任一单词的并没有被匹配到。这也说明，短语匹配必须匹配完整短语
高亮搜索
高亮搜索简单来说，就是将我们检索到的内容进行高亮处理，默认情况下，会将检索到的内容加上em标签：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query" : {
"match_phrase" : {
"about" : "rock climbing"
}
},
"highlight": {
"fields" : {
"about" : {}
}
}
}
'
返回结果：
{
"took" : 116,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : 1.8434994,
"hits" : [
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "4",
"_score" : 1.8434994,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to rock climbing",
"interests" : [
"sports",
"music"
]
},
"highlight" : {
"about" : [
"I love to <em>rock</em> <em>climbing</em>"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "3",
"_score" : 1.7099125,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
},
"highlight" : {
"about" : [
"I love to go <em>rock</em> <em>climbing</em>"
]
}
}
]
}
}
当然，高亮样式是支持自定义的：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query" : {
"match_phrase" : {
"about" : "rock climbing"
}
},
"highlight": {
"pre_tags" : ["<p style="color:red">"],
"post_tags" : ["</p>"],
"fields" : {
"about" : {}
}
}
}
'
返回结果：
{
...
"hits" : {
...
"hits" : [
{
...
},
"highlight" : {
"about" : [
"I love to <p style="color:red">rock</p> <p style="color:red">climbing</p>"
]
}
},
{
...
},
"highlight" : {
"about" : [
"I love to go <p style="color:red">rock</p> <p style="color:red">climbing</p>"
]
}
}
]
}
}
数据分析
下面我们就来看下简单的数据统计，下面的表达式是按age进行分组，统计数据。这在es的专业术语叫聚合查询，类似于传统SQL中的group by，和传统的SQL很像：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"aggs": {
"all_interests": {
"terms": { "field": "age" }
}
}
}
'
返回结果：
{
"took" : 3,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 9,
"relation" : "eq"
},
"max_score" : 1.0,
"hits" : [
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "1",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 15,
"about" : "I love to go reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "2",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to climbing go rock",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "3",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "4",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to rock climbing",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "5",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "6",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "7",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading and go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "8",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go and reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "9",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to do something",
"interests" : [
"sports",
"music"
]
}
}
]
},
"aggregations" : {
"all_interests" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [
{
"key" : 25,
"doc_count" : 8
},
{
"key" : 15,
"doc_count" : 1
}
]
}
}
}
从返回结果中，我们可以看出，age 为25的数据有8条，age为15的数据有1条。
query和aggs组合使用
这里的聚合查询aggs是可以和query同时存在的,，就和select name, count(*) from user group by name一样：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query" : {
"match" : {
"about" : "go reading"
}
},
"aggs": {
"all_interests": {
"terms": { "field": "age" }
}
}
}
'
返回结果：
{
"took" : 10,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 7,
"relation" : "eq"
},
"max_score" : 1.1097689,
"hits" : [
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "1",
"_score" : 1.1097689,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 15,
"about" : "I love to go reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "6",
"_score" : 1.1097689,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "7",
"_score" : 1.0293508,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading and go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "8",
"_score" : 1.0293508,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go and reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "5",
"_score" : 0.7753851,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "2",
"_score" : 0.36634043,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to climbing go rock",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "3",
"_score" : 0.36634043,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
}
]
},
"aggregations" : {
"all_interests" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [
{
"key" : 25,
"doc_count" : 6
},
{
"key" : 15,
"doc_count" : 1
}
]
}
}
}
在返回结果中aggregations就是聚合查询的结果，buckets（桶）表示最后聚合结果，每个通（bucket）表示一条聚合结果。
更多集合检索用法
聚合查询的规则本身也是支持多个规则组合使用的，我们在上面的聚合查询中又加入了平均值的计算：
curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query" : {
"match" : {
"about" : "go reading"
}
},
"aggs": {
"all_interests": {
"terms": { "field": "age" }
},
"avg_age" : {
"avg" : { "field" : "age" }
}
}
}
'
返回结果：
{
"took" : 16,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 7,
"relation" : "eq"
},
"max_score" : 1.1097689,
"hits" : [
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "1",
"_score" : 1.1097689,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 15,
"about" : "I love to go reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "6",
"_score" : 1.1097689,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "7",
"_score" : 1.0293508,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading and go",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "8",
"_score" : 1.0293508,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go and reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "5",
"_score" : 0.7753851,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to reading",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "2",
"_score" : 0.36634043,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to climbing go rock",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "megacorp",
"_type" : "employee",
"_id" : "3",
"_score" : 0.36634043,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
}
]
},
"aggregations" : {
"avg_age" : {
"value" : 23.571428571428573
},
"all_interests" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [
{
"key" : 25,
"doc_count" : 6
},
{
"key" : 15,
"doc_count" : 1
}
]
}
}
}
总结
实话实说，elasticsearch的搜索语法确实还是很复杂的，截止到今天，按照官方文档内容的章节安排，搜索部分的入门内容已经结束了，但是我怎么觉得我像刚入门一样，还是对elasticsearch没有全面的认识。我看了下剩余的内容，咋感觉现在才算正式开始了——深入搜索、处理人类语言、聚合、地理位置、数据建模、监控等都没开始学习呢？
好吧，我承认以前对elasticsearch的认知太浅显了，它确实是一套独立的知识体系（而不是一门语言），从某种程度上说，elasticsearch重新定义了搜索，所以还是好好学习吧，干就对了！
今天周末，稍微放纵了下，刷了半天的剧，然后快到晚上才开始梳理相关内容，不过某种程度上我觉得我们还是比较自觉的，任务也算顺利完成了，明天得早点开始了。加油吧，少年！
最后，预告下明天要更新的内容，除了我们既定的elasticsearch之外，我还要完成7月份内容的更新，所以明天的内容还是比较多的。
好了，大家伙晚安吧！