[mapguide-internals] Code Reveiw request: Remove IsNull check when get property from feature source

[Traian Stanev]

The initial implementation for the rendering code indeed used optimistic null handling via try-catch instead of checking for IsNull, for performance reasons. For most data sets, not checking for null is a lot faster, because in FDO checking for IsNull gets the property value a second time. However, there were some sample data sets with lots of null values, which incurred a big overhead because of the number of catches that happened -- so someone added the IsNull. For such data, having the IsNull was a lot faster due to the inherent slowness of catching.

The facts have not changed since then -- removing the null check will make things faster for data sets with no null values but slower for data sets with lots of null values.

Really, MapGuide should not have to work around FDO being slow. There must be some way to optimize FDO providers where this is slow to cache the value after checking it for null and then quickly return it knowing that the next property value requested will likely be for the property that was previously checked for null.

Traian





-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Zac Spitzer
Sent: Wednesday, August 10, 2011 12:36 AM
To: MapGuide Internals Mail List
Subject: Re: [mapguide-internals] Code Reveiw request: Remove IsNull check when get property from feature source

that old thread was titled [mapguide-internals] Exception thrown on null values?

here is some of it, dates back to 08, which was pre-nabble days?

http://osgeo-org.1803224.n2.nabble.com/RE-mapguide-internals-Exception-thrown-on-null-values-td2051195.html

from my *limited* understanding, this patch catches any exceptions and then gracefully handles them which should be a big win

z


On Wed, Aug 10, 2011 at 2:28 PM, Jason Birch <jason at jasonbirch.com> wrote:
> Wasn't the isnull check initially put in place to deal with stability 
> issues (something to do with FDO exceptions not unwinding properly or 
> something?)
>  It was a long time ago, but it sounds pretty familiar.
>
> On 1 August 2011 01:15, Buddy Hu wrote:
>
>> Hi Lists,
>>
>> Please add your comments for this patch:
>> http://trac.osgeo.org/mapguide/ticket/1766
>>
>> Regards,
>> Buddy
>> _______________________________________________
>> mapguide-internals mailing list
>> mapguide-internals at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/mapguide-internals
>>
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--
Zac Spitzer
Solution Architect / Director
Ennoble Consultancy Australia
http://www.ennoble.com.au
http://zacster.blogspot.com
+61 405 847 168
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