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https://issues.apache.org/jira/browse/FLINK-3385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15154905#comment-15154905
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Greg Hogan commented on FLINK-3385:
-----------------------------------
Will submit the pull request when Travis has finished. There was an additional
fix, discovered with the unit tests running under severe memory constraints,
where {{processUnmatchedBuildIter}} would cause a {{NullPointerException}} when
all partitions had spilled to disk. That simple fix is included as a hotfix.
> Fix outer join skipping unprobed partitions
> -------------------------------------------
>
> Key: FLINK-3385
> URL: https://issues.apache.org/jira/browse/FLINK-3385
> Project: Flink
> Issue Type: Bug
> Components: Distributed Runtime
> Reporter: Greg Hogan
> Assignee: Greg Hogan
> Priority: Blocker
> Fix For: 1.0.0
>
>
> {{MutableHashTable.nextRecord}} performs three steps for a build-side outer
> join:
> {code}
> public boolean nextRecord() throws IOException {
> if (buildSideOuterJoin) {
> return processProbeIter() ||
> processUnmatchedBuildIter() || prepareNextPartition();
> } else {
> return processProbeIter() || prepareNextPartition();
> }
> }
> {code}
> {{MutableHashTable.processUnmatchedBuildIter}} eventually calls through to
> {{MutableHashTable.moveToNextBucket}} which is unable to process spilled
> partitions:
> {code}
> if (p.isInMemory()) {
> ...
> } else {
> return false;
> }
> {code}
> {{MutableHashTable.prepareNextPartition}} calls
> {{HashPartition.finalizeProbePhase}} which only spills the partition (to be
> read and processed in the next instantiation of {{MutableHashTable}}) if
> probe-side records were spilled. In an equi-join this is fine but with an
> outer join the unmatched build-side records must still be retained (though no
> further probing is necessary, so could this be short-circuited when loaded by
> the next {{MutableHashTable}}?).
> {code}
> if (isInMemory()) {
> ...
> }
> else if (this.probeSideRecordCounter == 0) {
> // partition is empty, no spilled buffers
> // return the memory buffer
>
> freeMemory.add(this.probeSideBuffer.getCurrentSegment());
> // delete the spill files
> this.probeSideChannel.close();
> this.buildSideChannel.deleteChannel();
> this.probeSideChannel.deleteChannel();
> return 0;
> }
> else {
> // flush the last probe side buffer and register this
> partition as pending
> this.probeSideBuffer.close();
> this.probeSideChannel.close();
> spilledPartitions.add(this);
> return 1;
> }
> {code}
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