[FLINK-3385] Fix outer join skipping unprobed partitions

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 1.0.0
• Component/s: Runtime / Coordination
• Assignee: Greg Hogan
• Reporter: Greg Hogan
• Created: 10/Feb/16 19:07
• Updated: 23/Feb/16 08:22
• Resolved: 23/Feb/16 08:22

Description

MutableHashTable.nextRecord performs three steps for a build-side outer join:

	public boolean nextRecord() throws IOException {
		if (buildSideOuterJoin) {
			return processProbeIter() || processUnmatchedBuildIter() || prepareNextPartition();
		} else {
			return processProbeIter() || prepareNextPartition();
		}
	}

MutableHashTable.processUnmatchedBuildIter eventually calls through to MutableHashTable.moveToNextBucket which is unable to process spilled partitions:

			if (p.isInMemory()) {
				...
			} else {
				return false;
			}

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?).

		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;
		}