Skip to main content

High Performance PL/SQL

PL/SQL is a key enabling technology in Oracle Database. You should make sure that you are aware of and take advantage appropriately key features of the PL/SQL language focused on performance.

I offer a short list of those features below, along with links to related resources. Most of this is also capture in this slide deck:



Key Performance Features

All of these are covered in the slide deck above; the links will take you to the documentation on these features. Click here for the overall section in the doc on performance and optimization.
But Don't Forget About SQL Optimization

Chances are you could take full advantage of all the features listed above and more in PL/SQL, and still end up with a slow application. That's because at the heart of every application built on Oracle Database are your SQL statements, and if those are not optimized, you can pretty much forget everything else.

Here are some links you might find helpful in this regard:

(list under construction - please offer your suggestions in Comments)

Comments

Popular posts from this blog

Running out of PGA memory with MULTISET ops? Watch out for DISTINCT!

A PL/SQL team inside Oracle made excellent use of nested tables and MULTISET operators in SQL, blending data in tables with procedurally-generated datasets (nested tables).  All was going well when they hit the dreaded: ORA-04030: out of process memory when trying to allocate 2032 bytes  They asked for my help.  The error occurred on this SELECT: SELECT  *    FROM header_tab trx    WHERE (generated_ntab1 SUBMULTISET OF trx.column_ntab)       AND ((trx.column_ntab MULTISET             EXCEPT DISTINCT generated_ntab2) IS EMPTY) The problem is clearly related to the use of those nested tables. Now, there was clearly sufficient PGA for the nested tables themselves. So the problem was in executing the MULTISET-related functionality. We talked for a bit about dropping the use of nested tables and instead doing everything in SQL, to avoid the PGA error. That would, however require lots of wo...

How to Pick the Limit for BULK COLLECT

This question rolled into my In Box today: In the case of using the LIMIT clause of BULK COLLECT, how do we decide what value to use for the limit? First I give the quick answer, then I provide support for that answer Quick Answer Start with 100. That's the default (and only) setting for cursor FOR loop optimizations. It offers a sweet spot of improved performance over row-by-row and not-too-much PGA memory consumption. Test to see if that's fast enough (likely will be for many cases). If not, try higher values until you reach the performance level you need - and you are not consuming too much PGA memory.  Don't hard-code the limit value: make it a parameter to your subprogram or a constant in a package specification. Don't put anything in the collection you don't need. [from Giulio Dottorini] Remember: each session that runs this code will use that amount of memory. Background When you use BULK COLLECT, you retrieve more than row with each fetch, ...

PL/SQL 101: Save your source code to files

PL/SQL is a database programming language. This means that your source code is compiled into  and executed from within the Oracle Database. There are many fantastic consequences of this fact, many of which are explored in Bryn Llewellyn's Why Use PL/SQL? whitepaper. But this also can mean that developers see the database as the natural repository for the original source code , and this is a bad mistake to make. It's not the sort of mistake any JavaScript or Java or php developer would ever make, because that code is not compiled into the database (well, you can  compile Java into the database, but that's not where 99.99% of all Java code lives). But it's a mistake that apparently too many Oracle Database developers make. So here's the bottom line: Store each PL/SQL program unit in its own file . Use a source code control system to manage those files. Compile them into the database as needed for development and testing. In other words: you should never kee...