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Subject: RE: Joins and performance
Date: Fri, 1 Jun 2007 16:28:39 +0200
Message-ID: 
 <C3339485BCFFE44299CE192B46142F2E3C0656@brussels.office.pagelink.nl>
Thread-topic: Joins and performance
Thread-index: AcXj6bk3fKUPuU0tEdq7qwBgCBBTdXAX898gAAHVLPAAAWDu4AAAo6sA
From: "Robert Kromkamp" <r.kromkamp@pagelink.nl>
To: "Apache Torque Users List" <torque-user@db.apache.org>

Hi Greg,

Thanks for you reply! I've used views before within Torque. But in that
case I've problems with inserts/update statements. How do you handle
these?

Regards,
Robert
=20

-----Original Message-----
From: Greg Monroe [mailto:Greg.Monroe@DukeCE.com]=20
Sent: Friday, June 01, 2007 4:15 PM
To: Apache Torque Users List
Subject: RE: Joins and performance

If this is a frequent/heavily used query, another way to deal with this
is to create a view and a matching Torque object.  There is a table
option that suppresses the SQL generation.  You can then just use the
Peer/Record object as like it was a normal table.

Note you may want to pay close attention to the indices requirements of
the underlying table.  If commonly used columns in a large join are not
index, it can be a BIG performance hit.

> -----Original Message-----
> From: Vitzethum, Daniel [mailto:Daniel.Vitzethum@gigatronik.com]
> Sent: Friday, June 01, 2007 9:40 AM
> To: Apache Torque Users List
> Subject: AW: Joins and performance
>=20
> Hi Robert,
>=20
> > If I've 100 companies (which are schools) and 200 buildings, I will=20
> > executes 100 * 200 queries to get all the employees.
>=20
> be sure to avoid this... sounds like a killer ;-)
>=20
> > In low level SQL
> > this query can be combined in one query. Is there a way to handle=20
> > this within Torque?
>=20
> In Torque, you can use the Criteria.addJoin() method to link two=20
> tables.
>=20
>=20
> Using that feature, you cannot use the Peer.doSelect() method, but=20
> have to use Peer.doSelectVillageRecords(), which will return all=20
> columns of all joined tables in a village Record object, with no big=20
> difference to plain JDBC in handling. If you need or want Torque data=20
> objects, you have to extract them one by one from the result set.
>=20
> For a project of us, we wrote a helper class named JoinHelper that=20
> does this business for you AND returns an tree of Torque objects. In=20
> your case, it would return COMPANY objects that can be queried for=20
> their BUILDINGs, which again know their EMPLOYEEs.
>=20
> Please search the thread about two years ago in Torque archive and the

> discussion about. JoinHelper massively uses reflection, but is tested=20
> quite well and in production. If you have more detailled questions...
> you're welcome.
>=20
>=20
> Daniel
>=20
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>=20
>=20

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