NHibernate如何使Criteria内部联接而又不使对象水化? [英] NHibernate How to make Criteria inner join without hydrating objects?

问题描述

一些快速的休眠问题:

我有sql表:

Item { Id, Name }
ItemRange { Id, Name }
ItemHasItemRange { Id, ItemId, ItemRangeId } 

映射很简单，因此我不会粘贴它们，ItemId和ItemRangeId是外键，Item类具有映射为懒惰包的ItemHasItemRanges集合.

Mappings are simple, so I will not paste them, the ItemId and ItemRangeId are foreign keys, Item class has ItemHasItemRanges collection mapped as lazy bag.

我想要所有特定于ItemRange的项目，但我不想检索关联的ItemRangeObjects，我只想进行内部联接以缩小结果范围.

I want all items which are in particular ItemRange, but I do not want to retrieve associated ItemRangeObjects, I just want to do inner join to narrow results.

当我这样做时:

c.CreateCriteria("Item", "i")
  .CreateAlias("ItemHasItemRanges", "ihpr", JoinType.InnerJoin)
  .Add(Restrictions.Eq("ihpr.ItemRange.Id", I18nHelper.CurrentItemRange.Id));

它工作正常，但是所有 ItemHasItemRange 对象也都已获取到 Item.ItemHasItemRanges 集合(映射为惰性)

It works fine, but all ItemHasItemRange objects are fetched as well to the Item.ItemHasItemRanges collections (which is mapped as lazy)

我不想获取Item.ItemHasItemRanges，因为这需要时间.我只想做内部联接来限制结果集.在NHibernate中有可能吗?

I do not want to fetch Item.ItemHasItemRanges, because it takes time. I just want to do inner join to limit result set. It is possible in NHibernate?

推荐答案

我发现问题出在其他地方. ItemHasItemRange表在ItemId和ItemRangeId上没有多个索引-ID在每个字段上只有单独的索引.这就是为什么性能如此差的原因.

I find out the problem was somewhere else. ItemHasItemRange table did not have multiple index on ItemId and ItemRangeId - id only had separate indexes on each field. Thats why performance was so poor.

但是NHibernate问题仍然有效-是否有可能为准则创建内部联接只是为了缩小结果范围，而不是获取通常是惰性的所有联接对象.

But NHibernate question is still valid - is it possible to create inner join for criteria only to narrow results and not to fetch all joined objects which normally are lazy.

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