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https://issues.apache.org/jira/browse/JENA-1212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15383928#comment-15383928
]
ASF GitHub Bot commented on JENA-1212:
--------------------------------------
Github user afs commented on a diff in the pull request:
https://github.com/apache/jena/pull/157#discussion_r71314599
--- Diff:
jena-arq/src/main/java/org/apache/jena/atlas/data/SortedDataBag.java ---
@@ -69,19 +69,81 @@
protected final ThresholdPolicy<E> policy;
protected final SerializationFactory<E> serializationFactory;
- protected final Comparator<? super E> comparator;
+ protected final CanAbortComparator comparator;
protected boolean finishedAdding = false;
protected boolean spilled = false;
protected boolean closed = false;
+ protected volatile boolean cancelled;
public SortedDataBag(ThresholdPolicy<E> policy,
SerializationFactory<E> serializerFactory, Comparator<? super E> comparator)
{
this.policy = policy;
this.serializationFactory = serializerFactory;
- this.comparator = comparator;
+ this.comparator = new CanAbortComparator(comparator);
}
+ private final class CanAbortComparator implements Comparator<E>
+ {
+ /**
+ The test for whether the sort has been cancelled is
+ performed every <code>cancelTestFrequency</code>
comparisons.
+ This reduces the (presumed) overhead of access to a
+ volatile boolean.
+ */
+ static final int cancelTestFrequency = 10000;
+
+ /**
+ Count of the number of times this comparator has been
called.
+ */
+ int count = 0;
+
+ final Comparator<? super E> baseComparator;
+
+ public CanAbortComparator(Comparator<? super E> comparator)
+ {
+ this.baseComparator = comparator;
+ }
+
+ @Override public int compare(E o1, E o2)
+ {
+ count += 1;
+ if (count % cancelTestFrequency == 0)
+ {
+ if (cancelled) throw new AbandonSort();
+ }
+ return baseComparator.compare(o1, o2);
+ }
+
+ /**
+ Sort the array <code>e</code> using this comparator
+ with the additional ability to abort the sort.
+ */
+ public boolean abortableSort(E[] e) {
+ try { Arrays.sort(e, this); }
--- End diff --
Yes - with two notes: both are easily testable:
What happens if the comparator throws an exception on a separate thread (I
expect the std library handles this somehow)?
Is there a risk that one sort impacts the whole server?
> allow ORDER BY sort to be cancelled
> -----------------------------------
>
> Key: JENA-1212
> URL: https://issues.apache.org/jira/browse/JENA-1212
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Reporter: christopher james dollin
> Priority: Minor
> Fix For: Jena 3.1.1
>
>
> When a query with an ORDER BY is cancelled, the component
> Arrays.sort() that sorts the chunk(s) of the result
> bindings runs to completion before the cancel finishes.
> [See QueryIterSort and SortedDataBag.]
> For a large result set, this results in a long wait
> before the cancelled request finally finishes. This
> can be inconvenient.
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