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https://issues.apache.org/jira/browse/FLINK-6817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16034977#comment-16034977
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ASF GitHub Bot commented on FLINK-6817:
---------------------------------------
Github user sunjincheng121 commented on a diff in the pull request:
https://github.com/apache/flink/pull/4055#discussion_r119896926
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/windows.scala
---
@@ -91,6 +91,10 @@ class OverWindowWithOrderBy(
*/
def as(alias: Expression): OverWindow = {
+ if (null == preceding) {
--- End diff --
For the strict system type, I recommend adding the
`OverWindowWithPreceding` class to guide the user to do the correct operation.
> Fix NPE when preceding is not set in OVER window
> ------------------------------------------------
>
> Key: FLINK-6817
> URL: https://issues.apache.org/jira/browse/FLINK-6817
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Reporter: Jark Wu
> Assignee: Jark Wu
> Priority: Minor
> Fix For: 1.4.0
>
>
> When preceding is not set in over window , a NPE will be thrown:
> {code}
> val result = table
> .window(Over orderBy 'rowtime as 'w)
> .select('c, 'a.count over 'w)
> {code}
> {code}
> java.lang.NullPointerException
> at org.apache.flink.table.api.OverWindowWithOrderBy.as(windows.scala:97)
> {code}
> Preceding must be set in OVER window, so should throw a more explicit
> exception not a NPE
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