如何在毫秒内将成千上万的记录更新到MySQL DB [英] How do I update thousands of records into MySQL DB in milliseconds
问题描述
我想在不到一秒钟的时间内将大约1万条记录更新到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.
I want to update about 10K records into MySQL DB in less than a second. I have written below code which takes about 6-8 seconds to update a list of records into DB.
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();
}
}
}
请告诉我您的意见,以优化此代码以提高性能.
Please let me know your inputs to optimize this code for performance improvement.
推荐答案
您可以将INSERT批处理到具有rewriteBatchedStatements=true
的临时表中,而不是批处理各个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...
Rather than batching the individual UPDATEs, you could batch INSERTs into a temporary table with rewriteBatchedStatements=true
and then use a single UPDATE statement to update the main table. On my machine with a local MySQL instance, the following code takes about 2.5 seconds ...
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);
...而该版本大约需要1.3秒:
... while this version takes about 1.3 seconds:
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);
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