aka*_*kai 3 elasticsearch elasticsearch-aggregation
Elasticsearch 版本：2.3.3
基本上标题说明了一切。如果reverse_nested在第二个嵌套聚合下使用，尽管文档似乎通过reverse_nested（参见结果中的最后一个"doc_count"字段）来限定范围，但它后面的聚合以某种方式不起作用。
这里我准备了一个例子 - 一个文档是一个包含入学日期和考试历史的学生。
映射：
{
"mappings": {
"students": {
"properties": {
"name": {
"type": "string"},
"enrollment": {
"type": "date"},
"exam_histories": {
"type": "nested",
"properties": {
"date": {
"type": "date"},
"subjects": {
"type": "nested",
"properties": {
"name": {
"type": "string"},
"score": {
"type": "short"}}}}}}}}}
测试文档：
{
"name": "John",
"enrollment": "2012-09-01T00:00:00+00:00",
"exam_histories": [
{
"date": "2016-05-05T00:00:00+00:00",
"subjects": [
{
"name": "math",
"score": 90}]}]}
聚合查询（没有实际意义）：
{
"aggs": {
"nested_exam_histories": {
"nested": {
"path": "exam_histories"},
"aggs": {
"date_buckets": {
"date_histogram": {
"field": "exam_histories.date",
"interval": "day"},
"aggs": {
"this_reverse_nested_does_work": {
"reverse_nested": {},
"aggs": {
"newest_enrollment": {
"max": {
"field": "enrollment"}}}},
"deep_nested_subjects": {
"nested": {
"path": "exam_histories.subjects"},
"aggs": {
"score_buckets": {
"terms": {
"field": "exam_histories.subjects.score"},
"aggs": {
"this_reverse_nested_doesnt_work": {
"reverse_nested": {},
"aggs": {
"newest_exam_date": {
"max": {
"field": "exam_histories.date"}}}}}}}}}}}}}}
结果：
...
"aggregations" : {
"nested_exam_histories" : {
"doc_count" : 1,
"date_buckets" : {
"buckets" : [ {
"key_as_string" : "2016-05-05T00:00:00.000Z",
"key" : 1462406400000,
"doc_count" : 1,
"this_reverse_nested_does_work" : {
"doc_count" : 1,
"newest_enrollment" : {
"value" : 1.3464576E12,
"value_as_string" : "2012-09-01T00:00:00.000Z"
}
},
"deep_nested_subjects" : {
"doc_count" : 1,
"score_buckets" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [ {
"key" : 90,
"doc_count" : 1,
"this_reverse_nested_doesnt_work" : {
"doc_count" : 1,
"newest_exam_date" : {
"value" : null
}
...
...您可以在其中看到聚合“newest_exam_date”不起作用。这是一个错误还是我做错了什么？
您需要使用该选项显式指定要“反向聚合”的嵌套对象path，否则它假定该字段位于根级别。
从文档中：
\n\n\n\n\n路径 - 定义应连接回哪个嵌套对象字段。默认为空，这意味着它会连接回根\n/主文档级别。该路径不能包含对位于verse_nested 所在的嵌套聚合\xe2\x80\x99s 嵌套\n 结构之外的嵌套\n 对象字段的引用。\n 示例:
\n
{\n "size":0,\n "aggs": {\n "nested_exam_histories": {\n "nested": {\n "path": "exam_histories"\n },\n "aggs": {\n "date_buckets": {\n "date_histogram": {\n "field": "exam_histories.date",\n "interval": "day"\n },\n "aggs": {\n "this_reverse_nested_does_work": {\n "reverse_nested": {},\n "aggs": {\n "newest_enrollment": {\n "max": {\n "field": "enrollment"\n }\n }\n }\n },\n "deep_nested_subjects": {\n "nested": {\n "path": "exam_histories.subjects"\n },\n "aggs": {\n "score_buckets": {\n "terms": {\n "field": "exam_histories.subjects.score"\n },\n "aggs": {\n "this_reverse_nested_doesnt_work": {\n "reverse_nested": {\n "path": "exam_histories"\n },\n "aggs": {\n "newest_exam_date": {\n "max": {\n "field": "exam_histories.date"\n }\n }\n }\n }\n }\n }\n }\n }\n }\n }\n }\n }\n }\n}\n结果：
\n\n {\n "took": 5,\n "timed_out": false,\n "_shards": {\n "total": 5,\n "successful": 5,\n "failed": 0\n },\n "hits": {\n "total": 2,\n "max_score": 0,\n "hits": []\n },\n "aggregations": {\n "nested_exam_histories": {\n "doc_count": 2,\n "date_buckets": {\n "buckets": [\n {\n "key_as_string": "2016-05-05T00:00:00.000Z",\n "key": 1462406400000,\n "doc_count": 2,\n "this_reverse_nested_does_work": {\n "doc_count": 2,\n "newest_enrollment": {\n "value": 1377993600000,\n "value_as_string": "2013-09-01T00:00:00.000Z"\n }\n },\n "deep_nested_subjects": {\n "doc_count": 2,\n "score_buckets": {\n "doc_count_error_upper_bound": 0,\n "sum_other_doc_count": 0,\n "buckets": [\n {\n "key": 90,\n "doc_count": 2,\n "this_reverse_nested_doesnt_work": {\n "doc_count": 2,\n "newest_exam_date": {\n "value": 1462406400000,\n "value_as_string": "2016-05-05T00:00:00.000Z"\n }\n }\n }\n ]\n }\n }\n }\n ]\n }\n }\n }\n}\n注意path第二个“反向聚合”中的选项：
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