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https://issues.apache.org/jira/browse/IGNITE-16158?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Maksim Timonin reassigned IGNITE-16158:
---------------------------------------
Assignee: Maksim Timonin
> QueryCursor.close CacheQuery doesn't cancel query
> -------------------------------------------------
>
> Key: IGNITE-16158
> URL: https://issues.apache.org/jira/browse/IGNITE-16158
> Project: Ignite
> Issue Type: New Feature
> Reporter: Maksim Timonin
> Assignee: Maksim Timonin
> Priority: Minor
>
> ```
> IgniteCache<Long, Person> cache = crd.createCache("CACHE");
> try (IgniteDataStreamer<Long, Person> streamer =
> ignite.dataStreamer(cache.getName()))
> { for (int i = 0; i < CNT; i++) streamer.addData((long)i, new
> Person(i)); }
> IndexQuery<Long, Person> qry = new IndexQuery<Long, Person>(Person.class, IDX)
> .setCriteria(lt("id", CNT / 2));
> QueryCursor cursor = cache.query(qry);
> cursor.close();
> }
> ```
> QueryCursor holds a future that will be completed with iterator over result
> data.
> Starting a query spawns a new thread locally that query cache in background,
> prepares data, and it completes the future with iterator. All affected nodes
> run such threads.
> But cancelling of query with `QueryCursor.close` doesn't cancel query, and it
> will prepare data that will never request. Also cancelling of query doesn't
> clean up iterator.
>
> For local query this issue doesn't lead to any memory leaks, and the future
> and the iterator will be cleaned up by GC later. But actually we can help to
> GC by avoiding preparing the data and by explicit cleaning of those
> structures.
>
> But for remote queries those structures spends memory. And closing of cursor
> has to cancel them.
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