es实现聚合
es通过agg实现聚合，详情可见 es文档
有时候查询es数据的时候可能需要实现多字段group by的功能，例如：
SELECT sum(item_count) from A group by field1, field2, field3要实现多个维度的聚合，需要嵌套的agg查询语句:
{ "query": { }, "aggs": { "field1": { "terms": { "field": "field1", "size": 2147483647 #设置一个大的分桶数，防止一次统计不完整 }, "aggs": { "field2": { "terms": { "field": "field2", "size": 2147483647 }, "aggs": { "field3": { "terms": { "field": "field3", "size": 2147483647 }, "aggs": { "sum_field": { "sum": { "field": "sum_field" } } } } } } } } }, "size": 0}用函数构建聚合语句的agg部分：
def build_query_aggs(fields, sum_field): agg_data = {} curr_field = agg_data for item in fields: curr_field[item] = { "terms": { "field": item, "size": 2147483647 }, "aggs": {} } curr_field = curr_field[item]["aggs"] curr_field[sum_field] = { "sum": { "field": sum_field } } return agg_data处理得到的数据，将其组织成list：
def build_es_aggs_data(data, fields, sum_field): curr_field = None res_data = [] if len(fields) > 0: curr_field = fields[0] else: return curr_buckets = data[curr_field]['buckets'] for item in curr_buckets: if len(fields) == 1: curr_data= {} curr_data[curr_field] = item['key'] curr_data[sum_field] = item[sum_field]["value"] res_data.append(curr_data) else: pre_data = deepcopy(build_es_aggs_data(item, fields[1:], sum_field)) for pre_item in pre_data: pre_item[curr_field] = item['key'] res_data.append(pre_item) return res_data