java_JDBC(3)

Batch和Fetch两个特性非常重要。
Batch相当于JDBC的写缓冲，Fetch相当于读缓冲

如果把JDBC类比为JAVA IO的话，
不使用Fetch和Batch相当于直接使用FileInputStream和FileOutputStream
而设置了Fetch和Batch相当于使用BufferedInputStream和BufferedOutputStream

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

public class Test {

private static int _1W = 10000;

private static List<String> list = new ArrayList<String>(100 * _1W);

static {

for (int i = 0; i < 10 * _1W; i++) {

list.add(String.valueOf(i));

}

}

public static void main(String[] args) throws ClassNotFoundException, SQLException {

long start = System.currentTimeMillis();

fetchRead();

long end = System.currentTimeMillis();

System.out.println((end - start) + "ms");

}

public static void batchWrite() throws SQLException, ClassNotFoundException {

// 1108ms

Class.forName("oracle.jdbc.OracleDriver");

Connection connection = DriverManager.getConnection("jdbc:oracle:thin:127.0.0.1:1521:orcl", "xxx", "xxx");

connection.setAutoCommit(false);

PreparedStatement cmd = connection.prepareStatement("insert into t values(?)");

for (int i = 0; i < list.size(); i++) {

cmd.setString(1, list.get(i));

cmd.addBatch();

if (i % _1W == 0) {

cmd.executeBatch();

}

}

cmd.executeBatch();

connection.commit();

}

public static void jdbcWrite() throws ClassNotFoundException, SQLException {

// 28189ms

Class.forName("oracle.jdbc.OracleDriver");

Connection connection = DriverManager.getConnection("jdbc:oracle:thin:127.0.0.1:1521:orcl", "xxx", "xxx");

connection.setAutoCommit(false);

PreparedStatement cmd = connection.prepareStatement("insert into t values(?)");

for (String s : list) {

cmd.setString(1, s);

cmd.execute();

}

connection.commit();

}

public static void jdbcRead() throws ClassNotFoundException, SQLException {

// 3120ms

Class.forName("oracle.jdbc.OracleDriver");

Connection connection = DriverManager.getConnection("jdbc:oracle:thin:127.0.0.1:1521:orcl", "xxx", "xxx");

connection.setAutoCommit(false);

PreparedStatement cmd = connection.prepareStatement("select * from t");

ResultSet rs = cmd.executeQuery();

int i = 0;

while (rs.next()) {

rs.getString(1);

i = i + 1;

}

System.out.println("count:" + i);

}

public static void fetchRead() throws ClassNotFoundException, SQLException {

//764ms

Class.forName("oracle.jdbc.OracleDriver");

Connection connection = DriverManager.getConnection("jdbc:oracle:thin:127.0.0.1:1521:orcl", "xxx", "xxx");

connection.setAutoCommit(false);

PreparedStatement cmd = connection.prepareStatement("select * from t");

cmd.setFetchSize(_1W);

ResultSet rs = cmd.executeQuery();

int i = 0;

while (rs.next()) {

rs.getString(1);

i = i + 1;

}

System.out.println("count:" + i);

}

}