可以使用pl/sql的大批量sql特性来降低sql和pl /sql之间的通信开销。FORALL语句将INSERT或UPDATE或DELETE批次处理,BULK COLLECT子句带回批结果。如果,DML语句影响四个或更多个数据库行,使用bulk sql(批量SQL)可以显著提高性能。 1.FORALL语句的使用 但是,FORALL语句只能重复单独一条 DML语句。 例子:FORALL语句一次性...
可以参见下面的两个图,可以看到其实在pl/sql中,可能很多时候我们所写的pl/sql代码会在sql引擎和plsql引擎建进行上下文的切换,这个过程还是很耗费时间的。 而forall却是相反,是提供一次上下文切换,会在forall的过程中进行数据的包装处理。一次发送给sql执行器去处理,大大减少了上下文切换时间。 对于此,可以想象,如果...
当PL/SQL运行引擎执行一个代码块时,引擎本身只会处理过程语句,而SQL语句是发送给SQL引擎执行。SQL语句的执行时是由数据库的SQL引擎负责,再将执行结果返回给PL/SQL引擎。 以下是PL/SQL引擎运行原理: 这种PL/SQL引擎和SQL引擎之间的控制转移叫做上下文切换。每次发生切换时,都会有额外的开销。通过FORALL语句和BULK COL...
http://blog.itpub.net/23718752/viewspace-1289696/ 其实不光是bulk collect,forall对于pl/sql的性能的提升也是相当大的。 可以参见下面的两个图,可以看到其实在pl/sql中,可能很多时候我们所写的pl/sql代码会在sql引擎和plsql引擎建进行上下文的切换,这个过程还是很耗费时间的。 而forall却是相反,是提供一次上下...
Pl/SQL与SQL引擎之间的通信则称之为上下文切换。过多的上下文切换将带来过量的性能负载。 因此为减少性能...
PL/SQL is Oracle's procedural extension to industry-standard SQL. PL/SQL naturally, efficiently, and safely extends SQL for developers. Its primary strength is in providing a server-side, stored procedural language that is easy-to-use, seamless with SQL,
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The problem at hand is how to return all of the required data within a SQL construct. Table-valued functions are the answer. Table-valued functions are somewhat similar to the previous functions, but vary in two distinct ways. First, the attributes applied to the method m...