xxq250
/
homework-jianmu
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Wiki Activity

Update 14-stream.md

This commit is contained in:
Haojun Liao 2023-04-26 16:33:23 +08:00 committed by GitHub
parent cf57a3f3f6
commit a98cf1277f
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 32 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
docs/en/12-taos-sql/14-stream.md
View File

@ -13,8 +13,11 @@ Because stream processing is built in to TDengine, you are no longer reliant on
```sql
CREATE STREAM [IF NOT EXISTS] stream_name [stream_options] INTO stb_name SUBTABLE(expression) AS subquery
stream_options: {
TRIGGER [AT_ONCE | WINDOW_CLOSE | MAX_DELAY time]
WATERMARK time
TRIGGER [AT_ONCE | WINDOW_CLOSE | MAX_DELAY time]
WATERMARK time
IGNORE EXPIRED [0|1]
DELETE_MARK time
FILL_HISTORY [0|1]
}
```
@ -141,3 +144,30 @@ The data in expired windows is tagged as expired. TDengine stream processing pro
2. Recalculate the data. In this method, all data in the window is reobtained from the database and recalculated. The latest results are then returned.
In both of these methods, configuring the watermark is essential for obtaining accurate results (if expired data is dropped) and avoiding repeated triggers that affect system performance (if expired data is recalculated).
## Supported functions
All scalar functions are available in stream processing.
All System Information Functions are <b>not</b> available for stream processing.
All aggregate and selection functions are available in stream processing, except following functions
- [leastsquares](../function/#leastsquares)
- [percentile](../function/#percentile)
- [top](../function/#leastsquares)
- [bottom](../function/#top)
- [elapsed](../function/#leastsquares)
- [interp](../function/#elapsed)
- [derivative](../function/#derivative)
- [irate](../function/#irate)
- [twa](../function/#twa)
- [histogram](../function/#histogram)
- [diff](../function/#diff)
- [statecount](../function/#statecount)
- [stateduration](../function/#stateduration)
- [csum](../function/#csum)
- [mavg](../function/#mavg)
- [sample](../function/#sample)
- [tail](../function/#tail)
- [unique](../function/#unique)
- [mode](../function/#mode)