Question

我想在不到一秒的时间内将大约10K记录更新到MySQL数据库中。我写了下面的代码，大约需要6-8秒才能将记录列表更新到DB中。

public void updateResultList(List<?> list) {
            String user = "root";
            String pass = "root";
            String jdbcUrl = "jdbc:mysql://12.1.1.1/db_1?useSSL=false";
            String driver = "com.mysql.jdbc.Driver";
            PreparedStatement pstm = null;

            try {
                Class.forName(driver);
                Connection myConn = DriverManager.getConnection(jdbcUrl, user, pass);
                myConn.setAutoCommit(false);
                for(int i=0; i<list.size(); i++) {
                    Object[] row = (Object[]) list.get(i);
                    int candidateID = Integer.valueOf(String.valueOf(row[0]));
                    String result = String.valueOf(row[14]);
                    int score = Integer.valueOf(String.valueOf(row[19]));
                    String uploadState = (String) row[20];

                    String sql = "UPDATE personal_info SET result = ?, score = ?, uploadState = ? "
                                + " WHERE CandidateID = ?";

                    pstm = (PreparedStatement) myConn.prepareStatement(sql);
                    pstm.setString(1, result);
                    pstm.setInt(2, score);
                    pstm.setString(3, uploadState);
                    pstm.setInt(4, candidateID);
                    pstm.addBatch();
                    pstm.executeBatch();

                }
                myConn.commit();
                myConn.setAutoCommit(true);
                pstm.close();
                myConn.close();

            }
            catch (Exception exc) {
                exc.printStackTrace();
                try {
                    throw new ServletException(exc);
                } catch (ServletException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }   
       }

请让我知道您的输入以优化此代码以提高性能。

Answer 1

首先，您只需要初始化MethodError: all(::Reexport.##2#6, ::Array{Any,1}) is ambiguous.一次，您需要在prepareStatement循环

之前初始化它

其次，对于每个循环，你应该避免执行for它需要花费更多的资源，你需要执行它达到指定的数量，例如100,500或更多，也不要在{{1}之外执行它只循环一次，因为它会花费更多的内存资源

pstm.executeBatch();

Answer 2

您的pstm.executeBatch()应该在for循环

之后

参考How to insert List into database

Answer 3

您可以将INSERT批处理到具有rewriteBatchedStatements=true的临时表，而不是批量处理单个UPDATE，然后使用单个UPDATE语句来更新主表。在具有本地MySQL实例的计算机上，以下代码大约需要2.5秒......

long t0 = System.nanoTime();
conn.setAutoCommit(false);

String sql = null;
sql = "UPDATE personal_info SET result=?, score=?, uploadState=? WHERE CandidateID=?";
PreparedStatement ps = conn.prepareStatement(sql);
String tag = "X";
for (int i = 1; i <= 10000; i++) {
    ps.setString(1, String.format("result_%s_%d", tag, i));
    ps.setInt(2, 200000 + i);
    ps.setString(3, String.format("state_%s_%d", tag, i));
    ps.setInt(4, i);
    ps.addBatch();
}
ps.executeBatch();
conn.commit();
System.out.printf("%d ms%n", (System.nanoTime() - t0) / 1000000);

...虽然此版本大约需要1.3秒：

long t0 = System.nanoTime();
conn.setAutoCommit(false);

String sql = null;
Statement st = conn.createStatement();
st.execute("CREATE TEMPORARY TABLE tmp (CandidateID INT, result VARCHAR(255), score INT, uploadState VARCHAR(255))");
sql = "INSERT INTO tmp (result, score, uploadState, CandidateID) VALUES (?,?,?,?)";
PreparedStatement ps = conn.prepareStatement(sql);
String tag = "Y";
for (int i = 1; i <= 10000; i++) {
    ps.setString(1, String.format("result_%s_%d", tag, i));
    ps.setInt(2, 400000 + i);
    ps.setString(3, String.format("state_%s_%d", tag, i));
    ps.setInt(4, i);
    ps.addBatch();
}
ps.executeBatch();
sql = 
          "UPDATE personal_info pi INNER JOIN tmp ON tmp.CandidateID=pi.CandidateID "
        + "SET pi.result=tmp.result, pi.score=tmp.score, pi.uploadState=tmp.uploadState";
st.execute(sql);
conn.commit();
System.out.printf("%d ms%n", (System.nanoTime() - t0) / 1000000);

如何在几毫秒内将数千条记录更新到MySQL DB中

3 个答案: