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https://issues.apache.org/jira/browse/JDO-652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12930148#action_12930148
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Matthew T. Adams commented on JDO-652:
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I admit to not having followed the design discussions too closely, but there
was one line that tripped me up when reading your blog. It was the last
example, that of a subselect:
/* 1 */ TypesafeQuery<Product> tq = pm.newTypesafeQuery(Product.class);
/* 2 */ QProduct cand = QProduct.candidate();
/* 3 */ TypesafeSubquery tqsub = tq.subquery(Product.class, "q");
/* 4 */ QProduct candsub = QProduct.candidate("q");
/* 5 */ List<Product> results =
tq.filter(cand.value.lt(tqsub.select(candsub.value.avg()))).executeList();
On line 3, I expected to see TypesafeSubquery as a generic declaration,
TypesafeSubquery<Product>. I realize that that since it's coming from its
superselect instance (of type TypesafeQuery<Product>), the subselect can know
the type of the candidate class of its superselect.
Question 1: Why is the declaration not "TypesafeSubquery<Product>"?
Question 2: If the subselect queries the same candidate class as the
superselect, could we not provide an overload for TypesafeQuery<T>'s subquery
method that has the signature "TypesafeSubquery<T> subquery(string name)"?
> Provision of a typesafe refactor-friendly query capability for JDOQL
> --------------------------------------------------------------------
>
> Key: JDO-652
> URL: https://issues.apache.org/jira/browse/JDO-652
> Project: JDO
> Issue Type: New Feature
> Components: api, specification, tck
> Reporter: Andy Jefferson
> Fix For: JDO 3 maintenance release 1
>
>
> There are various querying capabilities of this type around. JPA2 has its
> Criteria query API. Third party solutions like QueryDSL also exist, in its
> case providing a JDOQL implementation (as well as JPQL, and HQL). We should
> seriously consider introducing something along these lines in the JDO2.4
> timeframe.
> There is a comparison of JPA Criteria with QueryDSL over at
> http://source.mysema.com/forum/mvnforum/viewthread_thread,49
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