Oren Eini

aka Ayende Rahien

Oren Eini

CEO of RavenDB

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Aug 04 2006

NHibernate and the second level cache bug: conclustions

time to read 2 min | 213 words

Well, I posted that the bug was fixed in the SVN repository, but it was merely moved to another location, not fixed. Futher investigating showed that the same issue appear in Hibernate.

Further investigation showed that this is by design. (Indeed, when trying to fix the "bug", I have run into the same conclustions, and was about to suggest the same "by-design" fix.)

The issue is, to remind you, deleting an object that reside in a collection on the second level cache. The Hibernate FAQ entry about the issue is here. The solution is very simple, you must remove the object from any collections in which it reside before you flush the changes to the database.

This is because NHibernate has no way (at least, no easy way, the suggestion that came up were very complex and fragile) to know in which collections this object reside in. The information exists, in theory, but applications make such wildly different usages of the collections that it is impossible to handle this in a general way.

All in all, this is a good solution, and I did get a chance to dive fairly deeply into NHibernate's code.

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Dmitry, Yes, but this is _known_ to be a 64 bits system - since we are allocating 3GB (not possible in 64 bits). Note t...

By Oren Eini on Answer: What does this code do?
That's why it is a good idea to compare the return value of `write` to the buffer size. "size_t" can be 32-bit on some system...

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There's a reason we miss `write_exact` and `read_exact` from the standard library. In fact, I am surprised the chunk is actua...

By Pyth0n on Challenge: What does this code do?
kpvleeuwen, I agree, unfortunately I don't have anyone to ask off the top of my head. Thanks, I fixed the headers.

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It could be interesting to reach out to storage firmware developers and ask what write patterns they think would be useful ex...

By kpvleeuwen on Performance discovery: IOPS vs. IOPS

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