Re: PL/SQL in SQL (12c feature)
- From: Tim Hall <tim@xxxxxxxxxxxxxxx>
- To: Hans Forbrich <fuzzy.graybeard@xxxxxxxxx>
- Date: Mon, 19 May 2014 16:00:18 +0100
My terminology could be slightly wrong here, but my understanding of this is...
The context switch is removed (or the effect minimized) by the PL/SQL
having an SQL call signature, rather than a PL/SQL call signature. A
stored procedure/function can have the same "benefit" by using PRAGMA
UDF.
The numbers certainly seem to stack up. Stored PL/SQL is slower than
PL/SQL in WITH clause. PL/SQL in WITH clause is slower than stored
PL/SQL defined with PRAGMA UDF.
A assume the latter is better as the stored PL/SQL is already compiled...
Cheers
Tim...
On Mon, May 19, 2014 at 3:41 PM, Hans Forbrich
<fuzzy.graybeard@xxxxxxxxx> wrote:
> On 19/05/2014 8:28 AM, McPeak, Matt wrote:
>>
>> My question is: if an in-line PL/SQL function calls a stored PL/SQL
>> function, does it all still execute without a context switch?
>
> From Steve Feuerstein's blog at
> http://www.oracle.com/technetwork/issue-archive/2013/13-sep/o53plsql-1999801.html
>
> "This approach offers a way to both “extend” the SQL language with
> application-specific functionality and reuse (rather than copy) algorithms.
> A downside of user-defined function execution in SQL is that it involves a
> context switch between the SQL and PL/SQL execution engines."
>
> and
>
> "So why would a developer want to copy logic from a PL/SQL function into a
> SQL statement? To improve performance. When I call my own PL/SQL function in
> a SQL statement, the SQL engine must perform a performance-affecting context
> switch to the PL/SQL engine. Moving the code inside the SQL statement means
> that that context switch no longer occurs."
>
> It appears the context switch still occurs outside of the inline PL/SQL
>
> My question would be "how did they eliminate the context switch in the first
> place?"
>
> /Hans
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