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From Jukka Zitting <jukka.zitt...@gmail.com>
Subject Re: [jr3 microkernel] Write skew
Date Wed, 30 Nov 2011 20:53:25 GMT
Hi,

On Wed, Nov 30, 2011 at 3:21 PM, Michael Dürig <mduerig@apache.org> wrote:
> 1) Does visible mean immediately visible on next access or visible after
> refresh? The second case would work with snapshot isolation.

That's up the implementation.

Section 10.11.1 of JSR 283 [1] explicitly allows changes to become
visible only after a refresh: "[...] items that do not have changes
pending have their state refreshed to reflect the current persisted
state, thus revealing changes made by other sessions."

More generally about the write skew -issue; I don't think that's a
common problem in practice. There aren't too many clients that
explicitly interleave operations of multiple sessions within a single
thread. And in a multithreaded setup a client would even with
Jackrabbit 2.x need to use explicit synchronization to enforce more
complex content constraints.

[1] http://www.day.com/specs/jcr/2.0/10_Writing.html#10.11.1%20Refresh

BR,

Jukka Zitting

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