Java JDBC忽略setFetchSize？ [英] Java JDBC ignores setFetchSize?

问题描述

我正在使用以下代码

 st = connection.createStatement(
            ResultSet.CONCUR_READ_ONLY,
            ResultSet.FETCH_FORWARD,
            ResultSet.TYPE_FORWARD_ONLY
             );
 st.setFetchSize(1000);
 System.out.println("start query ");
 rs = st.executeQuery(queryString);
 System.out.println("done query");

查询返回大量（800k）行，印刷开始查询和完成查询。当我在查询中手动设置limit 10000时，start和done之间没有时间。处理结果需要时间，所以我想它的总体更快，如果它只是从数据库中获取1k行，处理这些，当它的行不足，它可以在后台获得新的。

The query return a lot of (800k) rows and it take a large time (~2m) between printing "start query" and "done query". When I manually put an "limit 10000" in my query there's no time between "start" and "done". Processing the results takes time so I guess it's overall faster if it just fetches 1k rows from the database, processes those and when it's running out of rows it can get new ones in the background.

ResultsSet.CONCUR_READ_ONLY等其中我的最后猜测;

The ResultsSet.CONCUR_READ_ONLY etc where my last guess; am I missing something?

推荐答案

p>尝试关闭自动提交：

Try turning auto-commit off:

// make sure autocommit is off
connection.setAutoCommit(false);

 st = connection.createStatement();
 st.setFetchSize(1000);
 System.out.println("start query ");
 rs = st.executeQuery(queryString);
 System.out.println("done query");

参考

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