Question

我研究过sqlite，只是想问：一列中简单数据库中素数文件中的速度记录为4秒。没问题还是我有一些软件/硬件问题？在SQLite中写入4秒以上的256个笔记和（2ms用于非mysql文件编写）我简直不敢相信sqlite写得这么慢。

我的代码用于比较sqlite db work和file db work：

package demo_SQLite;

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;

public class demo_SQLite {

private static Connection conn;
private static Statement state;
private static File db = new File("datafile");

public static void main(String[] args) throws IOException {
    Debug("Start DB!");
    run();
}

private static void run() throws IOException {
    try {
        if (!db.exists()) {
            db.createNewFile();
        }
        Class.forName("org.sqlite.JDBC");
        conn = DriverManager.getConnection("jdbc:sqlite:" + db);
        state = conn.createStatement();

        state.executeUpdate("create table if not exists a(id integer,"
                + "time INT,"
                + "primary key (id));");

        PreparedStatement prep = conn.prepareStatement("insert into a values(?,?)");
        for (int i = 0; i < 257; i++) {
            int l = new Random().nextInt();
            prep.setInt(2, l);
            prep.execute();
        }
        prep.close();
        state.close();
        Debug("Done! (256)");
        file();
    } catch (Exception ex) {
        Logger.getLogger(Demo_MySQL.class.getName()).log(Level.SEVERE, null, ex);
    }
}

private static void file() {
    try {
        Debug("Start File!");
        File file = new File("filebase");
        DataOutputStream dos = null;
        dos = new DataOutputStream
        (new BufferedOutputStream(new FileOutputStream(file)));
        int r = 0;
        for (int i = 0; i < 257; ++i) {
            r = new Random().nextInt();
            dos.writeInt(r);
        }
        dos.flush();
        dos.close();
        Debug("Done! (256)");
    } catch (IOException ex) {
        Logger.getLogger(Demo_MySQL.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static void Debug(String msg) {
    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");
    Date date = new Date();
    System.out.println("[" + sdf.format(date) + "][DEBUG]: " + msg);
}
}

结果：

run:
[07:53:49.829][DEBUG]: Start DB!
[07:53:53.223][DEBUG]: Done! (256)
[07:53:53.223][DEBUG]: Start File!
[07:53:53.253][DEBUG]: Done! (256)
BUILD SUCCESSFUL (total time: 5 seconds)

4秒！哇！这很棒！请告诉我 - 这是正常的还是我做错了什么？

更新。

似乎是自动提交的问题。正如我刚刚读到的那样，“默认情况下，每个INSERT语句都是它自己的事务。但如果用BEGIN ... COMMIT包围多个INSERT语句，则所有插入都被分组到一个事务中。提交事务所需的时间在所有封闭的insert语句中分摊，因此每个insert语句的时间大大减少。“

我只是禁用自动提交 - 更正后的代码和新结果：

package demo_sqlite;

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;

public class demo_SQLite {

private static Connection conn;
private static Statement state;
private static File db = new File("datafile");

public static void main(String[] args) throws IOException {
Debug("Start DB!");
run();
}

private static void run() throws IOException {
try {
    if (!db.exists()) {
        db.createNewFile();
    }

    //run db driver
    Class.forName("org.sqlite.JDBC");
    conn = DriverManager.getConnection("jdbc:sqlite:" + db);
    state = conn.createStatement();

    //check table 
    state.executeUpdate("create table if not exists a(id integer,"
            + "time INT,"
            + "primary key (id));");
    conn.setAutoCommit(false);

    // clear table if table not clear
    state.execute("DELETE FROM a");
    conn.commit();

    //make needed notes for db
    PreparedStatement prep = conn.prepareStatement("insert into a values(?,?)");
    for (int i = 0; i < 256; ++i) {
        int l = new Random().nextInt();
        prep.setInt(2, l);
    prep.execute();
    }
    conn.commit();
    prep.close();

    //reading notes for chek
    List<Integer> notes = new LinkedList<Integer>();
    ResultSet res = state.executeQuery("select * from a");
    while (res.next()) { int n = res.getInt("time"); notes.add(n); }
    res.close();            
    state.close(); 
    Debug("Done! ("+ notes.size() + ")");

    //write to a file for comparing the write speed
    Debug("Start File!");
    File file = new File("filebase");
    DataOutputStream dos = null;
    dos = new DataOutputStream
    (new BufferedOutputStream(new FileOutputStream(file)));
    int r = 0;
    for (int i = 0; i < 256; ++i) {
        r = new Random().nextInt();
        dos.writeInt(r);
    }
    dos.flush();
    dos.close();
    Debug("Done! (256)");

    //done! see log for result
} catch (Exception ex) { }
}

public static void Debug(String msg) {
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");
Date date = new Date();
System.out.println("[" + sdf.format(date) + "][DEBUG]: " + msg);
}
}

结果：

run:
[09:01:36.890][DEBUG]: Start DB!
[09:01:37.052][DEBUG]: Done! (256)
[09:01:37.053][DEBUG]: Start File!
[09:01:37.054][DEBUG]: Done! (256)
BUILD SUCCESSFUL (total time: 0 seconds)

感谢大家的答案！但如果您对此有所考虑，请欢迎

Answer 1

我可能尝试不同的驱动程序。试试mySQL附带的那个： http://www.mysql.com/products/connector/

在MySQL Connector / J中实现java.sql.Driver的类的名称是com.mysql.jdbc.Driver。

SQLite写得很慢

1 个答案: