I think the reason (or maybe just one of them) for the
query sent is the assumption that you might not read all
the records all the time but only a few at a time, you
might even stop reading them in the middle of your
processing:
Collection c = yourBeanHome.findAll ();
// Suppose this returns 2000 records after executing
// SQL with no where (id = ?) or (id = ?)
Iterator i = c.iterator ();
int counter = 0;
while (i.hasNext ()) {
YourBean yb = (YourBean) i.next ();
if (counter > 5) { break; }
counter ++;
}
So in the scenario above you actually retireved only
five records. If you were not to have that strange
where statement in your SQL, you would waste creation
of exactly 1995 records. But since you did have it
you only wasted the retrieval of your ids and
<page-size> - 5 records. JBoss lets you manage this
situation thru that where and the settings in the
jbosscmp-jdbc.xml
<read-ahead>
<strategy>on-load</strategy>
<page-size>1000</page-size>
<eager-load-group>*</eager-load-group>
</read-ahead>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] Behalf Of Rafal
> Kedziorski
> Sent: Wednesday, February 26, 2003 6:57 AM
> To: [EMAIL PROTECTED]
> Subject: [JBoss-user] EntityBean findAll() method
>
>
> Hi,
>
> my every entity beas has findAll() method defined in ejb-jar.xml
> as follow:
>
> <query>
> <query-method>
> <method-name>findAll</method-name>
> <method-params/>
> </query-method>
> <ejb-ql><![CDATA[SELECT OBJECT(o) FROM firm o]]></ejb-ql>
> </query>
>
> Could be this done better by other mechanism? JBoss are generating this
> query for PostgreSQL:
>
> // get all id's
> LOG: query: SELECT t0_o.firm_id FROM firm t0_o
>
> // call for every id
> LOG: query:
> SELECT firm_id,name FROM firm WHERE (firm_id=1) OR (firm_id=2) OR
> (firm_id=1046258766552575) OR (firm_id=1046258766812847) OR
> (firm_id=1046258766781998) OR (firm_id=1046258766823725) OR (
> firm_id=1046258766815290) OR (firm_id=1046258766821931) OR
> (firm_id=1046258766808355) OR (firm_id=1046258766805899) OR
> (firm_id=1046258766840567) OR (firm_id=1046258766818653) OR
> (firm_id=1046258766857549) OR (firm_id=1046258766870043)
>
> ...
>
> LOG: query: SELECT firm_id,name FROM firm WHERE
> (firm_id=1046258766821931) OR (firm_id=1046258766808355) OR
> (firm_id=1046258766805899) OR (firm_id=1046258766840567) OR
> (firm_id=1046258766818653) OR (
> firm_id=1046258766857549) OR (firm_id=1046258766870043)
>
> ...
>
> LOG: query: SELECT firm_id,name FROM firm WHERE
> (firm_id=1046258766818653) OR (firm_id=1046258766857549) OR
> (firm_id=1046258766870043)
>
> ...
>
> LOG: query: SELECT firm_id,name FROM firm WHERE
> (firm_id=1046258766857549) OR (firm_id=1046258766870043)
>
> ...
>
> // last sql query
> LOG: query: SELECT firm_id,name FROM firm WHERE
> (firm_id=1046258766870043)
>
>
> why are sending JBoss not for every firm_id one query?
>
> I have other tables, where are stored much more values. which generate
> than longer query.
>
>
> Best Regards,
> Rafal
>
>
>
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