godfreyhe commented on a change in pull request #16963:
URL: https://github.com/apache/flink/pull/16963#discussion_r695592782
##########
File path: docs/content.zh/docs/dev/table/sql/queries/window-tvf.md
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@@ -282,4 +282,63 @@ Here is an example invocation on the Bid table:
+------------------+------------------+-------+
```
+### SESSION
+
+The session windows groups elements by sessions of activity. Session windows
do not overlap and do not have a fixed start and end time, in contrast to
`TUMBLE` windows and `HOP` windows. Instead a session window closes when it
does not receive elements for a certain period of time, i.e., when a gap of
inactivity occurred.
Review comment:
groups -> group
##########
File path: docs/content.zh/docs/dev/table/sql/queries/window-tvf.md
##########
@@ -282,4 +282,63 @@ Here is an example invocation on the Bid table:
+------------------+------------------+-------+
```
+### SESSION
+
+The session windows groups elements by sessions of activity. Session windows
do not overlap and do not have a fixed start and end time, in contrast to
`TUMBLE` windows and `HOP` windows. Instead a session window closes when it
does not receive elements for a certain period of time, i.e., when a gap of
inactivity occurred.
+
+The `SESSION` function specifies session gap which defines how long the period
of inactivity is. When this period expires, the current session closes and
subsequent elements are assigned to a new session window.
+
+{{< img src="/fig/session-windows.svg" alt="Session Windows" width="70%">}}
+
+The `SESSION` functions assigns windows based on a [time attribute]({{< ref
"docs/dev/table/concepts/time_attributes" >}}) column. The return value of
`SESSION` is a new relation that includes all columns of original relation as
well as additional 3 columns named "window_start", "window_end", "window_time"
to indicate the assigned window. The original time attribute "timecol" will be
a regular timestamp column after window TVF.
Review comment:
assigns -> assign
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