JackRabbit - 删除重复行
我在 Jackrabbit 用户列表上问过这个问题，但没有得到答案。
JCR-SQL2 不提供 SELECT DISTINCT （或类似的，据我所知）。 JCR 1.0 中的 SQL 或 XPATH 也不...人们如何解决这个问题？删除重复行的最佳方法是什么？
我读到有人正在迭代结果并将它们放入集合中。就我而言，由于可能存在大量结果，这种方法最终可能成本太高。
这里有人有建议吗？
I have asked this question on jackrabbit-users list but I didn't get an answer.
JCR-SQL2 doesn't provide a SELECT DISTINCT (or similar, AFAIK). Neither do SQL or XPATH in JCR 1.0... How are people getting around this?. What's the best way of removing duplicate rows?
I read that someone was iterating over the results and putting them in a Set. In my case, because of the possible huge number of results, that approach may end up being too costly.
Does anyone here have a suggestion?
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JCR 1.0（例如，JSR-170）或JCR 2.0（例如，JSR-283）中定义的查询语言都没有
SELECT DISTINCT的概念。执行此操作的唯一方法是手动处理结果并丢弃您已经看到的任何行（或节点）。使用一组路径或 Node 对象就可以了。这并不是太困难，但不幸的是它比应有的更难，并且正如您所提到的，如果有很多行和/或重复项，则可能会很昂贵。
这就是为什么 ModeShape 提供对 JCR-SQL2 查询的全面支持，但也允许使用
SELECT DISTINCT。事实上，ModeShape 支持许多其他功能，例如WHERE子句中的非相关子查询LIMIT n和OFFSET mUNION、INTERSECT和EXCEPTFULL OUTER JOIN和CROSS JOINBETWEENcriteriaIN和NOT INDEPTH和PATH动态操作数以及其他一些操作数。有关详细信息，请参阅
None of the query languages defined in JCR 1.0 (e.g., JSR-170) or JCR 2.0 (e.g., JSR-283) have a notion of
SELECT DISTINCT.The only way to do this is to process the results manually and throwing out any rows (or nodes) that you've already seen. Using a set of paths or Node objects would work. This isn't too difficult, but it's unfortunately harder than it should be and, as you mention, can be expensive if there are a lot of rows and/or duplicates.
This is why ModeShape provides full support for JCR-SQL2 queries but also allows use of
SELECT DISTINCT. In fact, ModeShape supports a number of other features such asWHEREclauseLIMIT nandOFFSET mUNION,INTERSECTandEXCEPTFULL OUTER JOINandCROSS JOINBETWEENcriteriaINandNOT INDEPTHandPATHdynamic operandsand a few others. For details, see the documentation.