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https://issues.apache.org/jira/browse/FLINK-7423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16133142#comment-16133142
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ASF GitHub Bot commented on FLINK-7423:
---------------------------------------
Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/4525
I think `null` values are not really permitted at the moment, but I think
the InputFormats do not explicitly forbid them. That's why the logic is not
"run until returns null", but "run until reachedEnd()".
The change here implements a mixed contract like "run until reachedEnd() or
returns null", which is more complicated to document, enforce, test, and
understand for users.
> Always reuse an instance to get elements from the inputFormat
> ---------------------------------------------------------------
>
> Key: FLINK-7423
> URL: https://issues.apache.org/jira/browse/FLINK-7423
> Project: Flink
> Issue Type: Bug
> Components: DataStream API
> Reporter: Xu Pingyong
> Assignee: Xu Pingyong
>
> In InputFormatSourceFunction.java:
> {code:java}
> OUT nextElement = serializer.createInstance();
> while (isRunning) {
> format.open(splitIterator.next());
> // for each element we also check if cancel
> // was called by checking the isRunning flag
> while (isRunning && !format.reachedEnd()) {
> nextElement =
> format.nextRecord(nextElement);
> if (nextElement != null) {
> ctx.collect(nextElement);
> } else {
> break;
> }
> }
> format.close();
> completedSplitsCounter.inc();
> if (isRunning) {
> isRunning = splitIterator.hasNext();
> }
> }
> {code}
> the format may return other element or null when nextRecord, that will may
> cause exception.
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