JDBC - setAutoCommit用于只读操作 [英] JDBC - setAutoCommit for read only operation

问题描述

假设我有一个通用的方法创建一个数据库连接：

Let's say I have a common method which creates a DB connection:

Connection getConnection() throws SQLException {
    Connection con = ... // create the connection
    con.setAutoCommit(false);
    return con;
}

我把 setAutoCommit（false）在这里调用，因此这种方法的调用者不必担心设置它。然而，这是一个坏的做法，如果调用者执行的操作只是读取数据？是否有额外的开销？

I put the setAutoCommit(false) call here so that callers of this method never have to worry about setting it. However, is this a bad practice if the operation executed by the caller is only reading data? Is there any extra overhead?

我个人认为最好将逻辑集中在一个地方，调用方不必设置自动提交，避免代码冗余。我只是想确保它不会对只读操作产生任何不必要的开销。

My personal opinion is that it's better to centralize the logic in one place, that way callers never have to set the auto commit and this avoids code redundancy. I just wanted to make sure it didn't incur any unnecessary overhead for a read only operation.

推荐答案

我把setAutoCommit（false）调用放在这里，以便这个方法的调用者不必担心设置它。

I put the setAutoCommit(false) call here so that callers of this method never have to worry about setting it.

这是很好的IMO，我个人认为，应该永远不要在应用程序中启用自动提交模式。所以我的建议是关闭自动提交。

This is fine IMO and I personally believe that one should never ever enable auto-commit mode inside an application. So my recommendation would be to turn off auto-commit.

但是，这是一个糟糕的做法，如果调用者执行的操作只有阅读数据？是否有额外的开销？

However, is this a bad practice if the operation executed by the caller is only reading data? Is there any extra overhead?

从严格的性能角度来看，它为每个SQL语句启动和结束数据库事务这可能会降低应用程序的性能。

From a strict performance point of view, it's starting and ending a database transaction for every SQL statement that has an overhead and may decrease the performance of your application.

顺便说一句，SELECT语句受 setAutoCommit（boolean） ：

By the way, SELECT statements are affected by setAutoCommit(boolean) according to the javadoc:

将此连接的自动提交
模式设置为给定状态。 如果
连接处于自动提交模式，
，则所有其SQL语句将
执行并作为单独的
事务提交。否则，它的SQL
语句被分组到
事务中，通过
调用方法commit或
终止方法rollback。默认情况下，新的
连接处于自动提交模式。

Sets this connection's auto-commit mode to the given state. If a connection is in auto-commit mode, then all its SQL statements will be executed and committed as individual transactions. Otherwise, its SQL statements are grouped into transactions that are terminated by a call to either the method commit or the method rollback. By default, new connections are in auto-commit mode.

当语句
完成时，语句
完成的时间取决于SQL的类型
语句：

The commit occurs when the statement completes. The time when the statement completes depends on the type of SQL Statement:

• 对于DML语句插入，更新或删除以及DDL语句
  语句在
  执行完后立即完成。


• 对于Select语句，语句


• 对于CallableStatement对象或返回多个
  结果的语句，语句完成
  当所有相关联的结果集
  已关闭，并且所有更新
  计数和输出参数已检索
  。

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