我现在正在使用批处理:
String query = "INSERT INTO table (id, name, value) VALUES (?, ?, ?)";
PreparedStatement ps = connection.prepareStatement(query);
for (Record record : records) {
ps.setInt(1, record.id);
ps.setString(2, record.name);
ps.setInt(3, record.value);
ps.addBatch();
}
ps.executeBatch();
我只是想知道上面的代码是否等同于以下代码。如果没有,哪个更快?
String query = "INSERT INTO table (id, name, value) VALUES ";
for (Record record : records) {
query += "(" + record.id + ",'" + record.name + "'," + record.value + "),";
}
query = query.substring(1, query.length() - 1);
PreparedStatement ps = connection.prepareStatement(query);
ps.executeUpdate();
首先,使用查询字符串连接,您不仅会丢失PreparedStatement方法的原生类型转换,而且还容易受到在数据库中执行的恶意代码的攻击。
其次,PreparedStatements以前被缓存在数据库本身中,这已经比普通语句提供了非常好的性能改进。
只要自动提交设置为false,executeBatch
将比executeUpdate
有更好的性能:
connection.setAutoCommit(false);
PreparedStatement ps = connection.prepareStatement(query);
for (Record record : records) {
// etc.
ps.addBatch();
}
ps.executeBatch();
connection.commit();
如果要插入的项目数很大,则可能会遇到严重的性能问题。因此,定义批量大小更安全,并在达到批量大小时不断执行查询。
类似下面的示例代码应该工作。有关如何有效使用此代码的完整故事,请参阅此link。
private static void insertList2DB(List<String> list) {
final int batchSize = 1000; //Batch size is important.
Connection conn = getConnection();
PreparedStatement ps = null;
try {
String sql = "INSERT INTO theTable (aColumn) VALUES (?)";
ps = conn.prepareStatement(sql);
int insertCount=0;
for (String item : list) {
ps.setString(1, item);
ps.addBatch();
if (++insertCount % batchSize == 0) {
ps.executeBatch();
}
}
ps.executeBatch();
} catch (SQLException e) {
e.printStackTrace();
System.exit(1);
}
finally {
try {
ps.close();
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public void insertBatch(final List<Record > records ) {
String query = "INSERT INTO table (id, name, value) VALUES (?, ?, ?)";
GenericDAO.getJdbcTemplate().batchUpdate(sql, new BatchPreparedStatementSetter() {
@Override
public void setValues(PreparedStatement ps, int i) throws SQLException {
Record record = records .get(i);
ps.setInt(1, record.id);
ps.setString(2, record.name);
ps.setInt(3, record.value);
}
@Override
public int getBatchSize() {
return records.size();
}
});
}
我认为这样做
String query = "INSERT INTO table (id, name, value) VALUES ";
for (Record record : records)
{
query += "(" + record.id + ",'" + record.name + "'," + record.value + "),";
query = query.substring(1, query.length() - 1);
PreparedStatement ps = connection.prepareStatement(query);
ps.executeUpdate();
}
因为您必须为每个要插入数据库的记录执行查询。