shuai.xu created FLINK-16011:
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Summary: Normalize the within usage in Pattern
Key: FLINK-16011
URL: https://issues.apache.org/jira/browse/FLINK-16011
Project: Flink
Issue Type: Improvement
Components: Library / CEP
Affects Versions: 1.9.0
Reporter: shuai.xu
In CEP, we can use Pattern.within() to set a window in which the pattern should
be matched. However, the usage of within is ambiguous and confusing to user.
For example:
# Pattern.begin("a").within(t1).followedBy("b").within(t2) will use the
minimal of t1 and t2 as the window time for the whole pattern.
# Pattern.begin("a").followedBy("b").within(t2) will use t2 as the window time.
# But Pattern.begin("a").within(t1).followedBy("b") will have no window time
# While
Pattern.begin("a").notFollowedBy("not").within(t1).followedBy("b").within(t2)
will use t2 as the window time.
So I propose to normalize the usage of within() and make strict checking when
compiling the pattern.
For example, we can only allow within() at the end of the pattern and point it
out if user set it somewhere else when compiling the pattern.
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