Apache TinkerPop•3mo ago

CollectingBarrierStep bug

Anyone ever notice this bug in the CollectingBarrierStep? Offending line https://github.com/apache/tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/CollectingBarrierStep.java#L81

    @Override
    public boolean hasNextBarrier() {
        this.processAllStarts();
        return !this.traverserSet.isEmpty();
    }

    @Override
    public boolean hasNextBarrier() {
        this.processAllStarts();
        return !this.traverserSet.isEmpty();
    }

The problem here is that if you had an input of X + Y elements where X is your collecting barrier size and Y is some number greater than 0, if the first X elements in the barrier have no results output in the barrier and the latter Y elements in the barrier do have some result, the barrier will only be called on the first X elements and will not execute a second time.

GitHub

tinkerpop/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/p...

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Solution:

Overriding this function seems to fix ``` @Override public Traverser.Admin<Vertex> processNextStart() {...

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2 Replies

LyndonOP•3mo ago

found out that is not actual the offending line. Not sure what is but the statement about barrier not executing the next section is still true actual issue seems to stem from AbstractStep @Override public boolean hasNext() { if (EmptyTraverser.instance() != this.nextEnd) return true; else { try { while (true) { if (Thread.interrupted()) throw new TraversalInterruptedException(); this.nextEnd = this.processNextStart(); if (this.nextEnd.bulk() > 0) return true; else this.nextEnd = EmptyTraverser.instance(); } } catch (final NoSuchElementException e) { return false; } } } the no such element exception is producing from the collecting barrier

Solution

Lyndon•3mo ago

Overriding this function seems to fix

    @Override
    public Traverser.Admin<Vertex> processNextStart() {
        try {
            return super.processNextStart();
        } catch (final NoSuchElementException e) {
            if (!this.starts.hasNext())
                throw e;
            return EmptyTraverser.instance();
        }
    }

    @Override
    public Traverser.Admin<Vertex> processNextStart() {
        try {
            return super.processNextStart();
        } catch (final NoSuchElementException e) {
            if (!this.starts.hasNext())
                throw e;
            return EmptyTraverser.instance();
        }
    }

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CollectingBarrierStep bug