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java - 使用 Scala foreach 处理 CQEngine ResultSet 非常慢

转载 作者:行者123 更新时间:2023-11-30 09:14:05 27 4
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我正在尝试使用 Scala 的 foreach 处理 CQEngine 的 ResultSet,但结果非常慢。

以下是我正在尝试做的事情的片段

import collection.JavaConversions._
val query = existIn(myOtherCollection, REFERENCE, REFERENCE)
val resultSet = myIndexCollection.retrieve(query)
resultSet.foreach(r =>{
//do something here
})

不知何故 .foreach 方法非常慢。我尝试通过放置 SimonMonitor 进行调试并使用 while(resultSet.hasNext) 更改 .foreach,令人惊讶的是,每次调用 hasNext 方法大约需要 1-2 秒。这非常慢。

我尝试使用 Java 创建相同的版本,Java 版本 super 快。

请帮忙

最佳答案

我无法使用以下测试代码重现您的问题。你能在你的系统上试一下吗?让我知道它是如何运行的?

(取消注释第 38 行,garages.addIndex(HashIndex.onAttribute(Garage.BRANDS_SERVICED)),使 Scala 和 Java 迭代器都运行得非常快...)

首先输出(时间以毫秒为单位):

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

代码如下:

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 <- 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 <- 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 => {
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()
}
}
}

关于java - 使用 Scala foreach 处理 CQEngine ResultSet 非常慢,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20675164/

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