把SELECT count(DISTINCT user_id) from rams_ol_case语句转为elasticsearch语句
时间: 2023-11-27 09:06:00 浏览: 40
在 Elasticsearch 中,可以使用聚合(Aggregation)功能来实现类似于 SQL 中 `SELECT count(DISTINCT user_id) from rams_ol_case` 的查询。具体的实现步骤如下:
1. 创建一个索引并插入数据,例如:
```
PUT my_index/_doc/1
{
"user_id": 1,
"case_name": "case1"
}
PUT my_index/_doc/2
{
"user_id": 2,
"case_name": "case2"
}
PUT my_index/_doc/3
{
"user_id": 1,
"case_name": "case3"
}
PUT my_index/_doc/4
{
"user_id": 3,
"case_name": "case4"
}
```
2. 使用聚合功能进行去重计数,例如:
```
POST my_index/_search
{
"size": 0,
"aggs": {
"distinct_users": {
"cardinality": {
"field": "user_id"
}
}
}
}
```
这个聚合查询会对 `user_id` 字段进行去重计数,得到不同的用户数。执行结果如下:
```
{
"took": 3,
"timed_out": false,
"_shards": {
"total": 1,
"successful": 1,
"skipped": 0,
"failed": 0
},
"hits": {
"total": {
"value": 4,
"relation": "eq"
},
"max_score": null,
"hits": []
},
"aggregations": {
"distinct_users": {
"value": 3
}
}
}
```
这个结果表明,不同的用户数是 3。