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https://issues.apache.org/jira/browse/FLINK-7423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16125010#comment-16125010
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ASF GitHub Bot commented on FLINK-7423:
---------------------------------------
Github user greghogan commented on the issue:
https://github.com/apache/flink/pull/4525
`MutableObjectIterator#next` allows/requires a `null` result: "@return The
object or <code>null</code> if the iterator is exhausted.". The documentation
could be improved, e.g. in `MergeIterator` the returned object is not
necessarily the immediately passed argument.
`DataSourceTask` looks to be the only `InputFormat` consumer re-passing a
reuse object.
It seems the reason to allow returning `null` is handling, for example, a
bad record at the end of a file, such that `reachedEnd` would have returned
`false` but there is no record to return.
Object reuse is always optional so is not an issue for immutable types.
> 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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