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How to use eclipselink.batch with em.find()? [message #1064252]

Tue, 18 June 2013 12:24

Markus KARG

Messages: 28
Registered: June 2011

Junior Member

It is common sense that eclipselink.batch hint will speed up queries. But how can this be used to speed up @OneToMany relationships when running em.find()? As the query is implied, one doesn't know the QL Name to provide as the value of eclipselink.batch!

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Re: How to use eclipselink.batch with em.find()? [message #1064301 is a reply to message #1064252]

Tue, 18 June 2013 15:04

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

You can only use a batch fetch on a query that returns multiple objects. find() only returns a single objects, so batch fetching would have not benefit.

If you are trying to batch fetch a relationship of the target of the OneToMany, then you could use the @BatchFetch annotation on the target's relationship.

James : Wiki : Book : Blog : Twitter

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Re: How to use eclipselink.batch with em.find()? [message #1064403 is a reply to message #1064301]

Wed, 19 June 2013 06:28

Markus KARG

Messages: 28
Registered: June 2011

Junior Member

Okay I forgot to mention that the single entity returned has a fetch=EAGER relationship with loads lots of child entities. That is what I want to speed up. Smile

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Re: How to use eclipselink.batch with em.find()? [message #1064404 is a reply to message #1064403]

Wed, 19 June 2013 06:30

Markus KARG

Messages: 28
Registered: June 2011

Junior Member

I know that I can use @BatchFetch Annotation. The problem is that my code must not load Eclipse-specific classes, since it must stay portable. So I *must* use a hint at the em.find() command. I should have told the whole story right from the start to make it more clear.

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Re: How to use eclipselink.batch with em.find()? [message #1065379 is a reply to message #1064404]

Tue, 25 June 2013 13:52

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

You can also define @BatchFetch in your EclipseLink orm.xml.

You could probably also change your find() to instead use a Query and define the batch fetch on both the relationship and the child relationship.

RE: one doesn't know the QL Name to provide as the value of eclipselink.batch
Well this QL name is ignored anyway, you should be able to put any alias you want there as long as the syntax is correct.

James : Wiki : Book : Blog : Twitter

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