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);

    }

}