Elasticsearch 简明教程
Elasticsearch - Aggregations
聚合框架收集搜索查询选择的所有数据，并包含许多构建模块，有助于构建数据的复杂摘要。此处显示了聚合的基本结构：
"aggregations" : {
"" : {
"" : {
}
[,"meta" : { [] } ]?
[,"aggregations" : { []+ } ]?
}
[,"" : { ... } ]*
}有不同类型的聚合，每种聚合都有自己的目的。本章将详细讨论它们。
Avg Aggregation
此聚合用于获取存在于聚合文档中的任何数字字段的平均值。例如，
POST /schools/_search
{
"aggs":{
"avg_fees":{"avg":{"field":"fees"}}
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 41,
"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"
}
}
]
},
"aggregations" : {
"avg_fees" : {
"value" : 2850.0
}
}
}Cardinality Aggregation
此聚合给出特定字段的不同值的计数。
POST /schools/_search?size=0
{
"aggs":{
"distinct_name_count":{"cardinality":{"field":"fees"}}
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 2,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"distinct_name_count" : {
"value" : 2
}
}
}Note − 基数的值为 2，因为费用中有两个不同的值。
Extended Stats Aggregation
此聚合生成聚合文档中特定数字字段的所有统计信息。
POST /schools/_search?size=0
{
"aggs" : {
"fees_stats" : { "extended_stats" : { "field" : "fees" } }
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 8,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"fees_stats" : {
"count" : 2,
"min" : 2200.0,
"max" : 3500.0,
"avg" : 2850.0,
"sum" : 5700.0,
"sum_of_squares" : 1.709E7,
"variance" : 422500.0,
"std_deviation" : 650.0,
"std_deviation_bounds" : {
"upper" : 4150.0,
"lower" : 1550.0
}
}
}
}Max Aggregation
此聚合找到聚合文档中特定数字字段的最大值。
POST /schools/_search?size=0
{
"aggs" : {
"max_fees" : { "max" : { "field" : "fees" } }
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 16,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"max_fees" : {
"value" : 3500.0
}
}
}Min Aggregation
此聚合找到聚合文档中特定数字字段的最小值。
POST /schools/_search?size=0
{
"aggs" : {
"min_fees" : { "min" : { "field" : "fees" } }
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 2,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"min_fees" : {
"value" : 2200.0
}
}
}Sum Aggregation
此聚合计算聚合文档中特定数字字段的总和。
POST /schools/_search?size=0
{
"aggs" : {
"total_fees" : { "sum" : { "field" : "fees" } }
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 8,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"total_fees" : {
"value" : 5700.0
}
}
}还有一些其他度量聚合在特殊情况下使用，它们包括用于地理位置的地理边界聚合和地理中心聚合。
Stats Aggregations
多值度量聚合，它对从聚合文档中提取的数字值计算统计数据。
POST /schools/_search?size=0
{
"aggs" : {
"grades_stats" : { "stats" : { "field" : "fees" } }
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 2,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"grades_stats" : {
"count" : 2,
"min" : 2200.0,
"max" : 3500.0,
"avg" : 2850.0,
"sum" : 5700.0
}
}
}Aggregation Metadata
您可以通过使用元标记在请求时添加一些有关聚合的数据，并可以在响应中获取它。
POST /schools/_search?size=0
{
"aggs" : {
"avg_fees" : { "avg" : { "field" : "fees" } ,
"meta" :{
"dsc" :"Lowest Fees This Year"
}
}
}
}运行以上代码时，我们得到以下结果：-
{
"took" : 0,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"avg_fees" : {
"meta" : {
"dsc" : "Lowest Fees This Year"
},
"value" : 2850.0
}
}
}