es - elasticsearch - aggs - pipeline - bucket

世界上并没有完美的程序，但是我们并不因此而沮丧，因为写程序就是一个不断追求完美的过程。

问：bucket_sort有什么特点？
答：

问：bucket_sort如何使用？
答：

DELETe /bucket_sort_test

PUT /bucket_sort_test
{
  "mappings": {
    "properties": {
      "type": {"type": "integer"},
      "num": {"type": "integer"},
      "date": {"type": "date"}
    }
  }
}

POST /bucket_sort_test/_bulk
{"index": {"_id": 1}}
{"type": 1, "num": 3, "date": "1989-01-10"}
{"index": {"_id": 2}}
{"type": 2, "num": 7, "date": "1988-01-10"}
{"index": {"_id": 3}}
{"type": 1, "num": 5, "date": "1990-01-10"}
{"index": {"_id": 4}}
{"type": 2, "num": 9, "date": "1990-01-10"}
{"index": {"_id": 5}}
{"type": 1, "num": 6, "date": "1989-01-10"}

GET /bucket_sort_test/_search
{
  "size": 0,
  "aggs": {
    "sort_aggs": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "year"
      },
      "aggs": {
        "sum_aggs": {
          "sum": {
            "field": "num"
          }
        },
        "bucket_sort_aggs": {
          "bucket_sort": {
            "sort": [{"sum_aggs": "desc"}],
            "from": 0,
            "size": 2
          }
        }
      }
    }
  }
}

# 结果
{
  "took" : 84,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 5,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "sort_aggs" : {
      "buckets" : [
        {
          "key_as_string" : "1990-01-01T00:00:00.000Z",
          "key" : 631152000000,
          "doc_count" : 2,
          "sum_aggs" : {
            "value" : 14.0
          }
        },
        {
          "key_as_string" : "1989-01-01T00:00:00.000Z",
          "key" : 599616000000,
          "doc_count" : 2,
          "sum_aggs" : {
            "value" : 9.0
          }
        }
      ]
    }
  }
}