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    <p>I am not able to reproduce your problem with the below test code. Can you try it on your system and let me know how it runs?</p> <p>(Uncomment line 38, <code>garages.addIndex(HashIndex.onAttribute(Garage.BRANDS_SERVICED))</code>, to make BOTH the Scala and Java iterators run blazingly fast...)</p> <p>The output first (time in milliseconds):</p> <pre><code>Done adding data Done adding index ============== Scala ============== Car{carId=4, name='BMW M3', description='2013 model', features=[radio, convertible]} Time : 3 seconds Car{carId=1, name='Ford Focus', description='great condition, low mileage', features=[spare tyre, sunroof]} Time : 1 seconds Car{carId=2, name='Ford Taurus', description='dirty and unreliable, flat tyre', features=[spare tyre, radio]} Time : 2 seconds ============== Java ============== Car{carId=4, name='BMW M3', description='2013 model', features=[radio, convertible]} Time : 3 seconds Car{carId=1, name='Ford Focus', description='great condition, low mileage', features=[spare tyre, sunroof]} Time : 1 seconds Car{carId=2, name='Ford Taurus', description='dirty and unreliable, flat tyre', features=[spare tyre, radio]} Time : 2 seconds </code></pre> <p>Code below:</p> <pre><code>import collection.JavaConversions._ import com.googlecode.cqengine.query.QueryFactory._ import com.googlecode.cqengine.CQEngine; import com.googlecode.cqengine.index.hash._; import com.googlecode.cqengine.IndexedCollection; import com.googlecode.cqengine.query.Query; import java.util.Arrays.asList; object CQTest { def main(args: Array[String]) { val cars: IndexedCollection[Car] = CQEngine.newInstance(); cars.add(new Car(1, "Ford Focus", "great condition, low mileage", asList("spare tyre", "sunroof"))); cars.add(new Car(2, "Ford Taurus", "dirty and unreliable, flat tyre", asList("spare tyre", "radio"))); cars.add(new Car(3, "Honda Civic", "has a flat tyre and high mileage", asList("radio"))); cars.add(new Car(4, "BMW M3", "2013 model", asList("radio", "convertible"))); // add cruft to try and slow down CQE for (i &lt;- 1 to 10000) { cars.add(new Car(i, "BMW2014_" + i, "2014 model", asList("radio", "convertible"))) } // Create an indexed collection of garages... val garages: IndexedCollection[Garage] = CQEngine.newInstance(); garages.add(new Garage(1, "Joe's garage", "London", asList("Ford Focus", "Honda Civic"))); garages.add(new Garage(2, "Jane's garage", "Dublin", asList("BMW M3"))); garages.add(new Garage(3, "John's garage", "Dublin", asList("Ford Focus", "Ford Taurus"))); garages.add(new Garage(4, "Jill's garage", "Dublin", asList("Ford Focus"))); // add cruft to try and slow down CQE for (i &lt;- 1 to 10000) { garages.add(new Garage(i, "Jill's garage", "Dublin", asList("DONT_MATCH_CARS_BMW2014_" + i))) } println("Done adding data") // cars.addIndex(HashIndex.onAttribute(Car.NAME)); // garages.addIndex(HashIndex.onAttribute(Garage.BRANDS_SERVICED)); println("Done adding index") val query = existsIn(garages, Car.NAME, Garage.BRANDS_SERVICED, equal(Garage.LOCATION, "Dublin")) val resultSet = cars.retrieve(query) var previous = System.currentTimeMillis() println("============== Scala ============== ") // Scala version resultSet.foreach(r =&gt; { println(r); val t = (System.currentTimeMillis() - previous) System.out.println("Time : " + t / 1000 + " seconds") previous = System.currentTimeMillis() }) println("============== Java ============== ") previous = System.currentTimeMillis() // Java version val i: java.util.Iterator[Car] = resultSet.iterator() while (i.hasNext) { val r = i.next() println(r); val t = (System.currentTimeMillis() - previous) System.out.println("Time : " + t / 1000 + " seconds") previous = System.currentTimeMillis() } } } </code></pre>
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    1. POProcessing CQEngine ResultSet with Scala foreach is very slow
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    1. COI forgot to mentioned that I'm trying to query from 2 IndexCollection. So the existsIn is used to query cars in collection 1 that also exists in collection 2 based on the attribute in your case is Car.NAME. I'll try to post more code tomorrow when I reach office
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    2. COI updated the code to a) do a exists-based join b) add a lot of cruft + NOT add an index so that CQEngine is forced to take time. In this case, both Scala and Java seem to take 1 to 3 seconds per lookup. If you add the index, `garages.addIndex(HashIndex.onAttribute(Garage.BRANDS_SERVICED))`, line 38, both Scala and Java finish the queries near-instantaneously...Do try this on your system and see if it gives you any insights into what is different about your code...?
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    3. COThanks for your updated code. There are 3 more things that can simulate my code. 1. The field being matched is created randomly using 5 characters alphanumeric (just upper case to make it easy) on object in both collections 2. Submit 1 million object on both IndexCollection. 3. Replace your existIn query to existsIn(garages, Car.NAME, Garage.BRANDS_SERVICED), just 3 parameters. I.e. remove your 4th parameter. That'll really simulate my code
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