apache derby - 解释选择 [英] apache derby - explain select

问题描述

我正在编写Java应用程序使用Apache Derby，我正在寻找等效的explain语句（例如为mySQL工作）。它不工作在德比。是否有类似的东西？

I'm programming Java application working with Apache Derby and i'm looking for equivalent for "explain" statement (working for mySQL for example). It's not working in Derby. Is there something similar?

推荐答案

有类似的事情：首先，有derby.language.logQueryPlan = true，计划信息添加到日志文件中： http://db.apache.org/ derby / docs / 10.8 / ref / rrefproper43414.html 。其次，有RUNTIMESTATISTICS功能，如果你想要可以捕获到您的程序的统计信息： http://db.apache.org/derby/docs/10.8/ref/rrefsqlj38831.html 。第三，有XPLAIN风格，它将查询计划信息捕获到数据库本身内的一组表中： http://db.apache.org/derby/docs/10.8/ref/rref_xplain_tables.html 。

There are similar things: Firstly, there is derby.language.logQueryPlan=true, which writes query plan information to the log file: http://db.apache.org/derby/docs/10.8/ref/rrefproper43414.html. Secondly, there is the RUNTIMESTATISTICS feature, which can capture the statistics into your program if you want: http://db.apache.org/derby/docs/10.8/ref/rrefsqlj38831.html. Thirdly, there is XPLAIN style, which captures query plan information into a set of tables inside your database itself: http://db.apache.org/derby/docs/10.8/ref/rref_xplain_tables.html.

您应该也花一些时间阅读： http://db.apache.org/derby /docs/10.8/tuning/ctundepth13055.html

You should probably also spend some time reading this: http://db.apache.org/derby/docs/10.8/tuning/ctundepth13055.html

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