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Update 14-stream.md

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Haojun Liao 2023-04-24 19:00:07 +08:00 committed by GitHub
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@ -213,3 +213,29 @@ DELETE_MARK time
``` ```
DELETE_MARK用于删除缓存的窗口状态，也就是删除流计算的中间结果。如果不设置，默认值是10年 DELETE_MARK用于删除缓存的窗口状态，也就是删除流计算的中间结果。如果不设置，默认值是10年
T = 最新事件时间 - DELETE_MARK T = 最新事件时间 - DELETE_MARK
## 流式计算支持的函数
1. 所有的单行函数均可用于流计算中。
2. 以下 19 个聚合函数不能在创建流计算的 SQL 语句中使用
```
leastsquares
percentile
top
bottom
elapsed
interp
derivative
irate
twa
histogram
diff
statecount
stateduration
csum
mavg
sample
tail
unique
mode
```