jdk8 stream實現sql單表select a,b,sum(),avg(),max() from group by a,b order by a,b limit M offset N及其性能

時間 2019-11-06

標籤 jdk8 jdk stream 實現 sql select sum avg max group order limit offset 及其性能欄目 Java 简体版

原文原文鏈接

之因此要測該場景，是由於merge多數據源結果的時候，有時候只是單個子查詢結果了，而此時採用sql數據庫處理並不必定可以合理（網絡延遲太大）。html

測試數據10萬行，結果1000行java

limit 20 offset 0的延時以下：sql

package com.hundsun.ta.base.service;

import com.hundsun.ta.utils.JsonUtils;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

import java.math.BigDecimal;
import java.util.*;
import java.util.stream.Collectors;

import static java.util.stream.Collectors.*;

/**
 * @author zjhua
 * @description
 * @date 2019/10/3 15:35
 */
public class JavaStreamCommonSQLTest {
    public static void main(String[] args) {
        List<Person> persons = new ArrayList<>();
        for (int i=100000;i>0;i--) {
            persons.add(new Person("Person " + (i+1)%1000, i % 100, i % 1000,new BigDecimal(i),i));
        }
        System.out.println(System.currentTimeMillis());
        Map<String,Map<Integer, Data>> result = persons.stream().collect(
                groupingBy(Person::getName,Collectors.groupingBy(Person::getAge,
                        collectingAndThen(summarizingDouble(Person::getQuantity),
                                dss -> new Data((long)dss.getAverage(), (long)dss.getSum())))));
        List<ResultGroup> list = new ArrayList<>();
        result.forEach((k,v)->{
            v.forEach((ik,iv)->{
                ResultGroup e = new ResultGroup(k,ik,iv.average,iv.sum);
                list.add(e);
            });
        });
        list.sort(Comparator.comparing(ResultGroup::getSum).thenComparing(ResultGroup::getAverage));
        list.subList(0,20);
        System.out.println(System.currentTimeMillis());
        System.out.println(JsonUtils.toJson(list));
    }
}

@lombok.Data@NoArgsConstructor@AllArgsConstructor
class Person {
    String name;
    int group;
    int age;
    BigDecimal balance;
    double quantity;
}

@lombok.Data@NoArgsConstructor@AllArgsConstructor
@Deprecated
class ResultGroup {
    String name;
    int group;
    long average;
    long sum;
}
class Data {
    long average;
    long sum;

    public Data(long average, long sum) {
        this.average = average;
        this.sum = sum;
    }

}

開始：1570093479002
結束：1570093479235 --200多毫秒數據庫

測試數據10萬行，結果90000行網絡

limit 20 offset 10000的延時以下：性能

package com.hundsun.ta.base.service;

import com.hundsun.ta.utils.JsonUtils;
import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

import java.math.BigDecimal;
import java.util.*;
import java.util.stream.Collectors;

import static java.util.stream.Collectors.*;

/**
 * @author zjhua
 * @description
 * @date 2019/10/3 15:35
 */
public class JavaStreamCommonSQLTest {
    public static void main(String[] args) {
        List<Person> persons = new ArrayList<>();
        for (int i=100000;i>0;i--) {
            persons.add(new Person("Person " + (i+1)%1000, i>90000 ? i%10000:i, i % 1000,new BigDecimal(i),i));
        }
        System.out.println(System.currentTimeMillis());
        Map<String,Map<Integer, Data>> result = persons.stream().collect(
                groupingBy(Person::getName,Collectors.groupingBy(Person::getGroup,
                        collectingAndThen(summarizingDouble(Person::getQuantity),
                                dss -> new Data((long)dss.getAverage(), (long)dss.getSum())))));
        List<ResultGroup> list = new ArrayList<>();
        result.forEach((k,v)->{
            v.forEach((ik,iv)->{
                ResultGroup e = new ResultGroup(k,ik,iv.average,iv.sum);
                list.add(e);
            });
        });
        list.sort(Comparator.comparing(ResultGroup::getSum).thenComparing(ResultGroup::getAverage));
        System.out.println(list.size());
        list.subList(10000,10020);
        System.out.println(System.currentTimeMillis());
        System.out.println(JsonUtils.toJson(list));
    }
}

@lombok.Data@NoArgsConstructor@AllArgsConstructor
class Person {
    String name;
    int group;
    int age;
    BigDecimal balance;
    double quantity;
}

@lombok.Data@NoArgsConstructor@AllArgsConstructor
@Deprecated
class ResultGroup {
    String name;
    int group;
    long average;
    long sum;
}
class Data {
    long average;
    long sum;

    public Data(long average, long sum) {
        this.average = average;
        this.sum = sum;
    }

}