Re: Eaten by the Tiger? Open Source WO is coming...

On Aug 24, 2005, at 2:46 PM, Alex Raftis wrote:

>
> On Aug 23, 2005, at 7:29 PM, Pierce T. Wetter III wrote:
>
>
>>   EOF used NSArrays in EOEditingContext and in many of the  
>> internal structures, so it ended being order(N) or order(N^2) for  
>> many operations. Its ok for fetching 20 objects, but if you fetch  
>> 10000...
>>
>>   You can see this in AJR in EOEditingContext when it has to see  
>> if it already has an object matching a given globalID, it has to  
>> scan an array.
>>
>>   NSSets would scale better.
>>
>
> Actually, NSSet would be useless, because you have to access  
> object's by global ID. NSSet only allows you to add objects, see if  
> an object exists, and iterate the objects. So, in this case, what  
> would help is to use NSDictionary's to access the objects, and this  
> is precisely what my EOEditingContext does. Only the public API's  
> use NSArray. For example, when you ask for the inserted objects,  
> you get back an NSArray, not the underlying NSDictionary. Yes, this  
> is a little cumbersome, but it allows us to match the EOF API,  
> which became an important consideration. Note that the array is  
> cached until the NSDictionary updates, after which point the array  
> has to be regenerated.
>
> BTW, as far as a concern for performance on object size, I've fetch  
> 100,000+ records from a DB and first object fetches (almost) as  
> fast as the last object. There's a slight degradation of  
> performance, since the underlying hash table gets pretty large, but  
> it's negligible. You'll only notice the slow town if you're closely  
> timing things.

   Which makes AJR much superior to EOF, as I commented, since EOF  
uses NSArrays, and the last object is definitely not as fast as the  
first object.

   I don't know where I got that AJR used NSArrays then, because I  
remember reading the header file for an EOEditingContext.h and seeing  
NSArray, and going "bummer" and moving on.

   So I apologize, and I'm much happier with AJR now. :-)

   Just out of curiousity, do you have any idea what the ratio of EOF  
overhead to database fetch time is? We found that it was 3x, that it  
took 3 times as long to fetch an object into EOF as it did to fetch  
raw rows from Frontbase. Some of that was building the objects  
(malloc, etc.) but a lot of it was registering the objects.


  Pierce