scan part-1

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## Scan查询
> [!WARNING]
> Apache Druid支持两种查询语言 [Druid SQL](druidsql.md) 和 [原生查询](makeNativeQueries.md)。该文档描述了原生查询中的一种查询方式。 对于Druid SQL中使用的该种类型的信息可以参考 [SQL文档](druidsql.md)。
Scan查询以流模式返回原始Apache Druid行。
除了向Broker发出扫描查询的简单用法之外还可以直接向Historical或流式摄取任务发出扫描查询。如果您希望并行地检索大量数据这将非常有用。
扫描查询对象示例如下所示:
```json
{
"queryType": "scan",
"dataSource": "wikipedia",
"resultFormat": "list",
"columns":[],
"intervals": [
"2013-01-01/2013-01-02"
],
"batchSize":20480,
"limit":3
}
```
以下为Scan查询的主要参数
| 属性 | 描述 | 是否必须 |
|-|-|-|
| `queryType` | | 是 |
| `dataSource` || 是 |
| `intervals` || 是 |
| `resultFormat` || 否 |
| `filter` || 否 |
| `columns` || 否 |
| `batchSize` || 否 |
| `limit` || 否 |
| `offset` || 否 |
| `order` || NONE |
| `legacy` || 否 |
| `context` || 否 |
### 示例结果
当resultFormat为 `list`时,结果格式如下:
```json
[{
"segmentId" : "wikipedia_editstream_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9",
"columns" : [
"timestamp",
"robot",
"namespace",
"anonymous",
"unpatrolled",
"page",
"language",
"newpage",
"user",
"count",
"added",
"delta",
"variation",
"deleted"
],
"events" : [ {
"timestamp" : "2013-01-01T00:00:00.000Z",
"robot" : "1",
"namespace" : "article",
"anonymous" : "0",
"unpatrolled" : "0",
"page" : "11._korpus_(NOVJ)",
"language" : "sl",
"newpage" : "0",
"user" : "EmausBot",
"count" : 1.0,
"added" : 39.0,
"delta" : 39.0,
"variation" : 39.0,
"deleted" : 0.0
}, {
"timestamp" : "2013-01-01T00:00:00.000Z",
"robot" : "0",
"namespace" : "article",
"anonymous" : "0",
"unpatrolled" : "0",
"page" : "112_U.S._580",
"language" : "en",
"newpage" : "1",
"user" : "MZMcBride",
"count" : 1.0,
"added" : 70.0,
"delta" : 70.0,
"variation" : 70.0,
"deleted" : 0.0
}, {
"timestamp" : "2013-01-01T00:00:00.000Z",
"robot" : "0",
"namespace" : "article",
"anonymous" : "0",
"unpatrolled" : "0",
"page" : "113_U.S._243",
"language" : "en",
"newpage" : "1",
"user" : "MZMcBride",
"count" : 1.0,
"added" : 77.0,
"delta" : 77.0,
"variation" : 77.0,
"deleted" : 0.0
} ]
} ]
```