[OJB-developers] OQLQueryImpl effieciency

[Charles A. <cha...@hp...>]

Hi all,

Whilst using OJB in a prototype, I found that using the standard
ojb.odmg.oql.OQLQueryImpl class to do an OQL query seemed a little
inefficient.

It turns out that this is because OQLQueryImpl uses a DList to return the
results as a collection. The DList implementation access the OJB_SEQ table
to gain an ID for itself, and one for each entry in the list. 

I have attached a quick-n-dirty try to improve on this; basically, I've
implemented a ManageableArrayList collection, which extends ArrayList and
implements ManageableCollection. I've also implemented a SpeedyQuery class,
which extends OQLQueryImpl and overrides execute to return a
ManageableArrayList instead of a DList. I've also attached a simple
CompareQueries class that tests the SpeedyQuery class.

In this test (against a table with 1889 rows on SQL server), the
OQLQueryImpl took on average 37 secs. The SpeedyQuery took 1.5 secs.

I'm sure there are drawbacks to this approach, and I'm sure that I've
overlooked something terribly important. The only things that I note at the
moment are :

* I'm not currently registering the resulting items with the current
transaction; this would be 
  trivial to achieve.
* If you remove or add an item to the ManageableArraylist, the changes would
not be propogated to 
  the database.

Still, even with those caveats (which I'm sure are possible to deal with), I
still think this speed improvement is not to be sniffed at. 

Comments are welcome; just be gentle with me - this is the first code I have
sent to an open-source mailing list....

With thanks,

Charles.


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