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https://issues.apache.org/jira/browse/IGNITE-20610?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Grigory Domozhirov updated IGNITE-20610:
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Summary: DataStreamer/KeyCacheObjectWrapper inefficiency for non-unique
keys (was: DataStreamerImpl.KeyCacheObjectWrapper low performance for
non-unique DataStreamer keys)
> DataStreamer/KeyCacheObjectWrapper inefficiency for non-unique keys
> -------------------------------------------------------------------
>
> Key: IGNITE-20610
> URL: https://issues.apache.org/jira/browse/IGNITE-20610
> Project: Ignite
> Issue Type: Task
> Components: streaming
> Affects Versions: 2.15
> Reporter: Grigory Domozhirov
> Priority: Minor
>
> While intention for https://issues.apache.org/jira/browse/IGNITE-3828 (Data
> streamer: use identity comparison for "activeKeys" in DataStreamerImpl.load0
> method) is clear it seems to work not as expected if allowOverwrite == true
> and same keys are added to a DataStreamer.
> With each DataStreamer.addData() a new UserKeyCacheObjectImpl() is created
> ([code|https://github.com/apache/ignite/blob/ceb22d20cab407b038570c81be022d7233a6e12d/modules/core/src/main/java/org/apache/ignite/internal/processors/cache/binary/CacheObjectBinaryProcessorImpl.java#L1316])
> for the key object and is added to GridConcurrentHashSet wrapped in a
> DataStreamerImpl.KeyCacheObjectWrapper
> ([code|https://github.com/apache/ignite/blob/fd504159bf5bc1603dfd5eb149ab5d998d3bffb4/modules/core/src/main/java/org/apache/ignite/internal/processors/datastreamer/DataStreamerImpl.java#L729]).
> Since its equals is overridden with identity check it ends up with
> `activeKeys` containing multiple objects with equal `UserKeyCacheObjectImpl`s
> and thus barely acts is a set.
>
> 1) Is that OK in general?
> 2) If yes, then does using GridConcurrentHashSet for activeKeys make any
> sense as all its entries are always non-equal?
> 3) Since `KeyCacheObjectWrapper.hashCode` returns actual key object's
> hashCode, the more often keys are repeated the lower performance is due to
> hash collisions of non-equal objects. Here is a corner case:
> {code:java}
> try (Ignite ignite = Ignition.start(new IgniteConfiguration());
> IgniteCache<Integer, Long> cache = ignite.createCache("test");
> IgniteDataStreamer<Integer, String> dataStreamer =
> ignite.dataStreamer(cache.getName())
> ) {
> dataStreamer.allowOverwrite(true); // doesn't matter
> long start = System.currentTimeMillis();
> for (int i = 0; i < 5_000_000; i++) {
> dataStreamer.addData(i, ""); //unique keys
> }
> System.out.println(System.currentTimeMillis() - start);
> }{code}
> runs in 6029 ms.
> {code:java}
> try (Ignite ignite = Ignition.start(new IgniteConfiguration());
> IgniteCache<Integer, Long> cache = ignite.createCache("test");
> IgniteDataStreamer<Integer, String> dataStreamer =
> ignite.dataStreamer(cache.getName())
> ) {
> dataStreamer.allowOverwrite(true); // doesn't matter
> long start = System.currentTimeMillis();
> for (int i = 0; i < 5_000_000; i++) {
> dataStreamer.addData(0, ""); //equal key
> }
> System.out.println(System.currentTimeMillis() - start);
> }{code}
> runs in 29025 ms.
>
>
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