Aggregation on a field and return the sum in elasticsearch

Question

I am working to find the way to do aggregations on a field after filtering on an another filed. But, the Elastic search documentation is not easily understandable.

Lets say My Mapping:

[
  {
     a:'a1'
     b:'b1'
     c:120
     d:12
   },
  {
     a:'a2'
     b:'b1'
     c:170
     d:15
   }
  {
     a:'a3'
     b:'b2'
     c:128
     d:18
   }
  {
     a:'a4'
     b:'b1'
     c:158
     d:5
   }
] 

Required Aggregation:

Return the sum of field "c", by selecting the docs with "b" where b=b1 and d is less than 13

This is not my requirement, but the answer helps me in understanding the documentation.

Answer 1

Try this:

POST index/_search
{
  "query": {
    "bool": {
      "must": [
        {
          "term": {
            "b": "b1"
          }
        },
        {
          "range": {
            "d": {
              "lt": 13
            }
          }
        }
      ]
    }
  },
  "aggs": {
    "total": {
      "sum": {
        "field": "c"
      }
    }
  }
}