apache derby - 解释选择
我正在使用 Apache Derby 编写 Java 应用程序,并且正在寻找“解释”语句的等效项(例如,适用于 mySQL)。这在德比中行不通。有类似的东西吗?
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?
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还有类似的东西:首先,有
derby.language.logQueryPlan=true
,它将查询计划信息写入日志文件:http://db.apache.org/derby/docs/10.8/ref/rrefproper43414.html。其次,还有RUNTIMESTATISTICS
功能,如果您愿意,它可以将统计信息捕获到您的程序中:http://db.apache.org/derby/docs/10.8/ref/rrefsqlj38831.html。第三,有 XPLAIN 样式,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。您可能还应该花一些时间阅读以下内容:http://db. apache.org/derby/docs/10.8/tuning/ctundepth13055.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 theRUNTIMESTATISTICS
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.You should probably also spend some time reading this: http://db.apache.org/derby/docs/10.8/tuning/ctundepth13055.html