[Zope-Coders] Re: [Zope-dev] Speaking of 2.6...

[Shane Hathaway]

Mario Valente wrote:
>   Hard links in Unix can be renamed. They rename the original object.

What do you mean?  Renaming a hard link does not rename the original file.


[shane@shane tmp]$ ls -l
total 11608
-rw-r--r--    1 shane    shane    11886453 Apr  8 12:11 procmail-log
[shane@shane tmp]$ ln procmail-log procmail-log2
[shane@shane tmp]$ ls -l
total 23216
-rw-r--r--    2 shane    shane    11886453 Apr  8 12:11 procmail-log
-rw-r--r--    2 shane    shane    11886453 Apr  8 12:11 procmail-log2
[shane@shane tmp]$ mv procmail-log2 procmail-log3
[shane@shane tmp]$ ls -l
total 23216
-rw-r--r--    2 shane    shane    11886453 Apr  8 12:11 procmail-log
-rw-r--r--    2 shane    shane    11886453 Apr  8 12:11 procmail-log3
[shane@shane tmp]$


What's even more interesting is that changing the file mode *does* 
propagate:


[shane@shane tmp]$ chmod a-w procmail-log
[shane@shane tmp]$ ls -l
total 23216
-r--r--r--    2 shane    shane    11886453 Apr  8 12:11 procmail-log
-r--r--r--    2 shane    shane    11886453 Apr  8 12:11 procmail-log3
[shane@shane tmp]$


>   Actually, if you look at the code, what Zope does right now is that an
>  object on the Zope tree is a hard link to an object on the ZODB. Zope just
>  doesnt allow multiple references to the object in the ZODB thus prohibiting
>  more than one hard link :-)

ZMI prohibits multiple references for a good reason.  I wrote the 
Symlink product a couple of years ago, and a few people tried it, but 
the ID problem was just too significant.  I tried changing attribute 
names without changing IDs, and it worked, but broke the ZMI.  I looked 
at different ways of resolving this, but the dual ID storage runs deep. 
  I thought about modifying acquisition to solve it, but at that point, 
I wasn't willing to work that hard. :-)

If you have a solid way to solve this issue and the security issues, 
links in Zope will be great.  But you can't ignore these issues.  In 
Zope 3 we're avoiding storing IDs in two places, and that will make a 
big difference.

Shane