Preceding Load Performance

[Anonymous]

Hello, i have read

Preceding Load

and https://www.quickintelligence.co.uk/preceding-load-qlikview/ but i still have some dubts about preceding load. Is this:

Load  ..., ReferenceDate,

   Age( ReferenceDate, BirthDate ) as Age;

Load  *,

   Date( FromDate + IterNo() – 1 ) as ReferenceDate

   Resident Policies

      While IterNo() <= ToDate - FromDate + 1 ;

Is faster than This:

TmpTable:

Load  *,

   Date( FromDate + IterNo() – 1 ) as ReferenceDate

   Resident Policies

      While IterNo() <= ToDate - FromDate + 1 ;

Table:

Load  ..., ReferenceDate,

   Age( ReferenceDate, BirthDate ) as Age

From TmpTable;

And Why. So It's preceding load doing some kind of shortcut or just a way to to don't have the need to have lots of temp tables when you do calculations like flags etc.

[olivierrobin]

i've also noticed a point (and retested just now)

if you do a preceding load, you loose the optimized load of a qvd

so in this case, it's better to do 2 load : 1 optimized from qvd, one from resident

[rwunderlich]

In the case of a preceding load, I found reloading from a QVD significantly faster than a Resident load. 2-3 times faster. I have test data going all the way back to V9.

In the Nov 2017 QV release, things have changed.  I believe the bugfix that Henric mentioned was released.  Testing against that release shows resident is now faster than qvd. Multi-processing is back!

The really excellent news is that I no longer see any penalty in using preceding load.  I'll do some more extensive testing and get a blog post out next week.

-Rob

http://masterssummit.com

http://qlikviewcookbook.com

[rwunderlich]

I've blogged about the performance update here

Preceding Load Performance Update | Qlikview Cookbook

-Rob

http://masterssummit.com

http://qlikviewcookbook.com