为了测试分布式定时任务的性能，以处理数据库数据为基础测试，所以需要在数据库里初始化一个表，大概是200w条数据。
1、因为是一个SpringBoot服务，spring提供的JdbcTemplate有批量插入的功能，所以自然想到直接用它，代码是这个样子：
private void initialDatabase() {
long beginTime = new Date().getTime();
final int total = 2*1000000;
jdbcTemplate.batchUpdate(initialDatabaseSql, new BatchPreparedStatementSetter() {
public void setValues(PreparedStatement preparedStatement, int i) throws SQLException {
preparedStatement.setString(1,String.valueOf(i));
preparedStatement.setString(2,"data for test timerTask");
}
public int getBatchSize() {
return total;
}
});
long endTime = new Date().getTime();
System.out.println("---------初始化数据完毕，耗时："+(endTime-beginTime)+"ms----------");
// System.exit(0);
}
但是结果确出人意料，平均耗时大概是372817ms/1w条，简直可怕，想到时间可能会长，但是没想到这么长，查了资料说要开启批量插入支持，debug了下确实走的批量插入，不明白，应该是哪里出了问题，毕竟这么成熟的框架，性能不至于这么差，之后会分析原因。
2、用框架不行，那就用最原始的JDBC操作了，直接用java.sql中的批量操作，代码是这个样子的：
private void initialDatabaseNewest() {
Connection connection = null;
PreparedStatement statement = null;
try {
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/timer?useUnicode=true&characterEncoding=utf-8","root","123456");
connection.setAutoCommit(false);
String sql = "insert into message(id,message,createTime) values(?,?,SYSDATE()) ";
statement = connection.prepareStatement(sql);
long begin = System.currentTimeMillis();
int i =0,j=1;
for (;j<100;j++) {
for (; i < 10000*j; i++) {
statement.setString(1,String.valueOf(i));
statement.setString(2,"data for test timerTask");
statement.addBatch();
}
statement.executeBatch();
}
connection.commit();
long end = System.currentTimeMillis();
System.out.println("---------初始化数据完毕，耗时："+(end-begin)+"ms----------");
}
catch (Exception e) {
e.printStackTrace();
}
finally {
try {
statement.close();
connection.close();
} catch (SQLException e) {
}
}
耗时2643ms/1w条，看着比之前快很多，但还是不够快，进入源码看看，虽然用的是Java自带的，算是往下了一层，但是这样的批量底层实现还是一条一条执行：
for(this.batchCommandIndex = 0; this.batchCommandIndex < nbrCommands; ++this.batchCommandIndex) {
Object arg = this.batchedArgs.get(this.batchCommandIndex);
try {
if (!(arg instanceof String)) {
PreparedStatement.BatchParams paramArg = (PreparedStatement.BatchParams)arg;
updateCounts[this.batchCommandIndex] = this.executeUpdateInternal(paramArg.parameterStrings, paramArg.parameterStreams, paramArg.isStream, paramArg.streamLengths, paramArg.isNull, true);
this.getBatchedGeneratedKeys(this.containsOnDuplicateKeyUpdateInSQL() ? 1 : 0);
} else {
updateCounts[this.batchCommandIndex] = this.executeUpdateInternal((String)arg, true, this.retrieveGeneratedKeys);
this.getBatchedGeneratedKeys(this.results.getFirstCharOfQuery() == 'I' && this.containsOnDuplicateKeyInString((String)arg) ? 1 : 0);
}
}
}
debug这里的时候发现了极其诡异的事，1和2都是走的上面这段代码，但是1慢了太多，不明白为啥。
debug时发现这么一段：
try {
this.statementBegins();
this.clearWarnings();
long[] var3;
if (!this.batchHasPlainStatements && this.connection.getRewriteBatchedStatements()) {
if (this.canRewriteAsMultiValueInsertAtSqlLevel()) {
var3 = this.executeBatchedInserts(batchTimeout); //***************************
return var3;
}
if (this.connection.versionMeetsMinimum(4, 1, 0) && !this.batchHasPlainStatements && this.batchedArgs != null && this.batchedArgs.size() > 3) {
var3 = this.executePreparedBatchAsMultiStatement(batchTimeout); //***************************
return var3;
}
}
var3 = this.executeBatchSerially(batchTimeout); //默认执行的是这一步 //***************************
return var3;
}
1和2默认都是走的executeBatchSerially这个方法，里面就是上一段代码那样一条一条遍历执行sql(不明白为啥时间差那么多)。那executeBatchedInserts呢？进入看一下：
for(int i = 0; i < ex; ++i) {
if (i != 0 && i % numValuesPerBatch == 0) {
try {
updateCountRunningTotal += batchedStatement.executeLargeUpdate();
} catch (SQLException var49) {
sqlEx = this.handleExceptionForBatch(batchCounter - 1, numValuesPerBatch, updateCounts, var49);
}
this.getBatchedGeneratedKeys(batchedStatement);
batchedStatement.clearParameters();
batchedParamIndex = 1;
}
//会循环执行这一步将参数值拼到一起
batchedParamIndex = this.setOneBatchedParameterSet(batchedStatement, batchedParamIndex, this.batchedArgs.get(batchCounter++));
}
try {
updateCountRunningTotal += batchedStatement.executeLargeUpdate();
}
在数据库连接串中加入rewriteBatchedStatements=true(感觉这样才是真正的batch处理)
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/timer?useUnicode=true&rewriteBatchedStatements=true"
debug看executeBatchedInserts方法中上面一段执行后PreparedStatement中的sql是这样的：
com.mysql.jdbc.PreparedStatement@3098eb37: insert into message(id,message,createTime)
values('0','data for test timerTask',SYSDATE())
,('1','data for test timerTask',SYSDATE())
,('2','data for test timerTask',SYSDATE())
,('3','data for test timerTask',SYSDATE())
,('4','data for test timerTask',SYSDATE())
,('5','data for test timerTask',SYSDATE())
... ...
果然这样确实批量处理了，耗时1405ms/1w条(开启了rewriteBatchedStatements后1和2时间差不多都是这么多)。
3、2中开启批量处理后可以看到就是相当于拼成了一条sql，那直接自己拼就可以省去框架的其他处理操作，是不是会快点？再试试最原始的一条sql，直接拼接成一条sql，代码是这个样子的：
private void initialDatabaseNew() {
Connection connection = null;
Statement statement = null;
try {
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/timer?useUnicode=true&characterEncoding=utf-8","root","123456");
connection.setAutoCommit(false);
statement = connection.createStatement();
long begin = System.currentTimeMillis();
int i =0,j=1;
for (;j<101;j++) { //这里分批是因为Mysql有大小限制，sql不能拼太长
StringBuffer sql = new StringBuffer("insert into message(id,message,createTime) values");
for (; i < 20000*j; i++) {
sql.append("('" + i + "','data for test timerTask',SYSDATE()),");
}
sql.append("('" + i++ + "','data for test timerTask',SYSDATE())");
statement.execute(sql.toString());
}
connection.commit();
long end = System.currentTimeMillis();
System.out.println("---------初始化数据完毕，耗时："+(end-begin)+"ms----------");
}
catch (Exception e) {
e.printStackTrace();
}
finally {
try {
statement.close();
connection.close();
} catch (SQLException e) {
}
}
耗时266ms/1w条，这个时间似乎可以接受。但是有没有更快的呢？毕竟现在还是停留在调用API，存储过程？还有其他？后续....
