Re: [Tm4j-developers] Topic.destroy() need to much time

[Kal A. <ka...@te...>]

Hi Rene,

At 14:45 07/02/2003 +0100, Ren...@da... wrote:
>Hi Kal,
>
>I just wanted to delete some topics from a topic map with 2000 Topics in it -
>with the api function topic.destroy().
>In some cases I have to delete nearly all topics (I apply some filters on it)
>and I woundered why I had to wait more then 10 minutes.
>I took the time of a single destroy() and it was about 300 ms on a 700 Mhz
>machine...

Ouch!

Is this with the in-memory backend or one of the persistent stores ?

Without running any profiling, my guess is that this performance hit comes 
because the code checks that the topic you are removing is not being used 
as a topic/association/occurrence/role type or in a scope. Because that 
information needs to be looked up from the indexes, you are getting hit 
with the cost of the lookups. There are a number of ways this could be fixed:

1) Add a reference count to Topic objects - so a Topic can only be 
destroyed if its ref count is 0
2) Consolidate all topic use information into a single index - so the cost 
is only one lookup, not 5

(2) is probably easier to implement and will not involve changing the 
database schema, but (1) would be more efficient. In fact, I could probably 
implement (1) for the Ozone and in-memory backends and make the 
implementation of the getRefCount() method on the RDBMS backend use a 
query.... that would be almost the best of both worlds....

But before I get into making these changes, I would like to get a bit of 
profiling on your problem. If you have time to do that for me, that would 
be really helpful as I am kind of pressed for time at the moment.

Cheers,

Kal