How to fetch from DB only few attributes instead all

szymic1 · **Joined:** Mon Feb 09, 2004 6:43 am **Posts:** 35

Hibernate version:
2.1.6
Database

Hi,
We process thousands of rows and we notice that execution time is fast but fetch time is rather long.
It is possible because our biggest object has 70 attributes, but for part of processing we need to read/update (there are no inserts) only let say 30-40% of attributes. Simply we can only fetch necessary data, that should minimize time of fetch (=sending to client + time of mapping to Java fields).

Is it possible to disable reading from table selected fields ?

Regards
Michal Szymanski
http://michal.szymanski.free.fr

Myk · **Joined:** Sun Jan 04, 2004 2:46 pm **Posts:** 147

Create a constructor on the object with lots of fields that only has the fields you want. Then run a query like:

Code:

select new WideObject( obj.firstField, obj.secondField ... obj.lastField ) from WideObject obj

Downside is that objects created in this fashion won't be in the session cache so if you change them you'll have to use the explicit session.update( wideObject ) to commit changes.

anthony · **Posted:** Sat Dec 18, 2004 5:57 pm

in hibernate 3 you have lazy at property level.
you're the first guy i see that can need it ;)

You should check
http://www.hibernate.org/41.html
that's what you need

max · **Posted:** Sun Dec 19, 2004 6:53 am

also look at dynamic-insert,dynamic-update to maybe improve the time used to update/insert time (test its actual effect since it differ on databases)

gavin · **Posted:** Sun Dec 19, 2004 7:02 am

Finally, check the "lightweight class" pattern on the Wiki.

max · **Posted:** Sun Dec 19, 2004 7:03 am

gavin - did you try to follow the link anthony showed ? :)

gavin · **Posted:** Sun Dec 19, 2004 7:12 am

oh. no. I thought Anthony was linking to something about <property lazy="true"/> ;-)

michael · **Posted:** Sun Dec 19, 2004 8:29 am

We should probably try to copy and paste the URL of the "Link" link in the topright corner of the page when posting Wiki URLs - e.g. http://www.hibernate.org/Documentation/LightweightClass for this one. I always forget about it, too, however.

max · **Posted:** Sun Dec 19, 2004 11:07 am

nice - actually didn't know it existed ;)

thank for that tip ...weird that the wiki internally uses the numbered nonhuman readable ones ;)

szymic1 · **Joined:** Mon Feb 09, 2004 6:43 am **Posts:** 35

Thank you for advice. First we have to confirm that "fetch time" is a issue in production environment. If yes we will use your advice. As I've promised at the and of the our project I will write short article about processing huge numbers of data using Hibernate ,- we have many advices that can be helpful for others. Currently our system produce about 1mln rows per day.

Thank you

christian · **Posted:** Mon Dec 20, 2004 5:42 pm

The "numeric" URLs in the wiki are more stable than the human readable links (which can change if you edit the title of the page).