wuchong commented on a change in pull request #10733:
[FLINK-15446][table][docs] Improve "Connect to External Systems" documentation
page
URL: https://github.com/apache/flink/pull/10733#discussion_r362380491
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File path: docs/dev/table/connect.md
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@@ -500,6 +501,39 @@ rowtime:
The following watermark strategies are supported:
<div class="codetabs" markdown="1">
+<div data-lang="DDL" markdown="1">
+{% highlight sql %}
+-- Sets a watermark strategy for strictly ascending rowtime attributes. Emits
a watermark of the
+-- maximum observed timestamp so far. Rows that have a timestamp smaller to
the max timestamp
+-- are not late.
+CREATE TABLE MyTable (
+ ts_field TIMESTAMP(3),
+ WATERMARK FOR ts_field AS ts_field
+) WITH (
+ ...
+)
+
+-- Sets a watermark strategy for ascending rowtime attributes. Emits a
watermark of the maximum
+-- observed timestamp so far minus 1. Rows that have a timestamp equal to the
max timestamp
+-- are not late.
+CREATE TABLE MyTable (
+ ts_field TIMESTAMP(3),
+ WATERMARK FOR ts_field AS ts_field - INTERVAL '0.001' SECOND
+) WITH (
+ ...
+)
+
+-- Sets a watermark strategy for rowtime attributes which are out-of-order by
a bounded time interval.
Review comment:
We don't have a shortcut API for this.
All the watermark strategies are expressed by expressions, we didn't provide
built-in strategy functions. So the `asceding timestamp` is a special case of
`out-of-order timestamp` which has a constant 1 ms delay.
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