此框架收集搜索查询选择的所有数据.该框架由许多构建块组成，这有助于构建复杂的数据摘要.聚合的基本结构如下所示:
"aggregations" : {
"<aggregation_name>" : {
"<aggregation_type>" : {
<aggregation_body>
}
[,"meta" : { [<meta_data_body>] } ]?
[,"aggregations" : { [<sub_aggregation>]+ } ]?
}
}有不同类型的聚合，每种聚合都有自己的目的和减号;
这些聚合有助于根据聚合文档的字段值计算矩阵，有时可以从脚本生成一些值.
数字矩阵单值，如平均聚合或多值，如 stats .
此聚合用于获取聚合文档中存在的任何数字字段的平均值.例如，
POST http://localhost:9200/schools/_search
{
"aggs":{
"avg_fees":{"avg":{"field":"fees"}}
}
}{
"took":44, "timed_out":false, "_shards":{"total":5, "successful":5, "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", "_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", "_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"
}
}
]
}, "aggregations":{"avg_fees":{"value":3233.3333333333335}}
}如果一个或多个聚合文档中不存在该值，则默认情况下将忽略它。 您可以在聚合中添加一个缺失字段，以将缺失值视为默认值。
{
"aggs":{
"avg_fees":{
"avg":{
"field":"fees"
"missing":0
}
}
}
}此聚合提供了特定字段的不同值的计数。 例如，
POST http://localhost:9200/schools*/_search
{
"aggs":{
"distinct_name_count":{"cardinality":{"field":"name"}}
}
}………………………………………………
{
"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"
},
{
"_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"
}
}, "aggregations":{"disticnt_name_count":{"value":3}}
………………………………………………注意:基数的值为3，因为名称中存在三个不同的值-政府，学校和示范。
此聚合生成有关聚合文档中特定数字字段的所有统计信息。 例如，
POST http://localhost:9200/schools/school/_search
{
"aggs" : {
"fees_stats" : { "extended_stats" : { "field" : "fees" } }
}
}………………………………………………
{
"aggregations":{
"fees_stats":{
"count":3, "min":2200.0, "max":5000.0,
"avg":3233.3333333333335, "sum":9700.0,
"sum_of_squares":3.609E7, "variance":1575555.555555556,
"std_deviation":1255.2113589175156,
"std_deviation_bounds":{
"upper":5743.756051168364, "lower":722.9106154983024
}
}
}
}
………………………………………………此聚合在聚合的文档中查找特定数字字段的最大值。 例如，
POST http://localhost:9200/schools*/_search
{
"aggs" : {
"max_fees" : { "max" : { "field" : "fees" } }
}
}………………………………………………
{
aggregations":{"max_fees":{"value":5000.0}}
}
………………………………………………此聚合在聚合的文档中查找特定数字字段的最大值。 例如，
POST http://localhost:9200/schools*/_search
{
"aggs" : {
"min_fees" : { "min" : { "field" : "fees" } }
}
}………………………………………………
"aggregations":{"min_fees":{"value":500.0}}
………………………………………………此聚合计算聚合文档中特定数字字段的总和。 例如，
POST http://localhost:9200/schools*/_search
{
"aggs" : {
"total_fees" : { "sum" : { "field" : "fees" } }
}
}………………………………………………
"aggregations":{"total_fees":{"value":10900.0}}
………………………………………………在特殊情况下还有其他一些度量标准聚合，例如地理边界聚合和地理质心聚合，以实现地理位置。
这些聚合包含用于具有标准的不同类型聚合的许多存储桶，该标准确定文档是否属于该存储桶。 桶聚合描述如下:
此存储桶聚合构成了一系列文档，这些文档被映射到父存储桶。 类型参数用于定义父索引。 例如，我们有一个品牌及其不同的模型，那么模型类型将具有以下_parent字段:
{
"model" : {
"_parent" : {
"type" : "brand"
}
}
}还有许多其他特殊的存储桶聚合，它们在许多其他情况下很有用，它们是:
Date Histogram Aggregation
Date Range Aggregation
Filter Aggregation
Filters Aggregation
Geo Distance Aggregation
GeoHash grid Aggregation
Global Aggregation
Histogram Aggregation
IPv4 Range Aggregation
Missing Aggregation
Nested Aggregation
Range Aggregation
Reverse nested Aggregation
Sampler Aggregation
Significant Terms Aggregation
Terms Aggregation
您可以在请求时使用meta标记添加一些有关聚合的数据，并作为响应获取。 例如，
POST http://localhost:9200/school*/report/_search
{
"aggs" : {
"min_fees" : { "avg" : { "field" : "fees" } ,
"meta" :{
"dsc" :"Lowest Fees"
}
}
}
}………………………………………………
{
"aggregations":{"min_fees":{"meta":{"dsc":"Lowest Fees"}, "value":2180.0}}
}
………………………………………………
