Re: [OJB-developers] Smart Updates

[Thomas M. <tho...@ho...>]

Hi Darren,

Darren Syzling wrote:

> I seem to remember testing a version of Object Bridge 0.7.235 that performed
> smart (or tuned) updates - only updating columns that had been modified.
> The documentation which came with this version mentioned this feature in a
> performance comparison with EJB.
>


These "Smart Update" feature has been kicked out a long time ago. May be 
it was still mentioned in the performance comparison. (I kicked out this 
documents as it is over a year old and totally out of date).

At the time of "smart updates" OJB did even use prepared statements. We 
used dynamically generated SQL that was generated for each update. No 
parameter binding. No caching of prepared statement.

Now OJB is working with prepared statements and uses a caching mechanism 
for these statements.
This setup brings an enormous performance gain for most application 
scenarios against most RDBMS.

Of course it would even be better to still have a smart update 
mechanism. but this would require to cache much MUCH more statements.
For N columns there are (if I remember correctly) (2^N) - 1 possible.
For a table with 10 coulums we had to cache more then 1000 statement !

That's why I dropped this feature.
My performance tests showed that using the cached prepared statement 
instead of dynamic "smart updates" has a much better performance.

 
HTH,


Thomas