Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-19 Thread Chris Withers
Jim Fulton wrote: Chris Withers wrote: Jim Fulton wrote: Even if you did track reads, how would you distinguish an unsafe read as above from a normal read that shouldn't cause a conflict? A write (or the undo of a write) would conflict with any reads in later transactions. Wouldn't that,

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-19 Thread Jim Fulton
Chris Withers wrote: Jim Fulton wrote: Chris Withers wrote: Jim Fulton wrote: Even if you did track reads, how would you distinguish an unsafe read as above from a normal read that shouldn't cause a conflict? A write (or the undo of a write) would conflict with any reads in later

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-18 Thread Jim Fulton
Chris Withers wrote: Jim Fulton wrote: ... Even if you did track reads, how would you distinguish an unsafe read as above from a normal read that shouldn't cause a conflict? A write (or the undo of a write) would conflict with any reads in later transactions. Jim -- Jim Fulton

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-17 Thread Chris Withers
Hi Jim, Jim Fulton wrote: BTW, I strongly discourage use of Undo except in emergencies. Sadly, except when undoing the last (non-undo) transactions in a database can lead to inconsistency. What sort of inconsistencies are you referring to? Undo can be a very attractive feature although

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-17 Thread Jim Fulton
Chris Withers wrote: Hi Jim, Jim Fulton wrote: BTW, I strongly discourage use of Undo except in emergencies. Sadly, except when undoing the last (non-undo) transactions in a database can lead to inconsistency. What sort of inconsistencies are you referring to? Logical inconsistencies.

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-17 Thread David Binger
On May 17, 2006, at 6:54 AM, Jim Fulton wrote: It was claimed earlier in this thread, that plone only lets you undo the most recent transactions. If this is true, then that should not be a problem. A facility that let you only undo last transactions would be safe. It would also be useful,

[ZODB-Dev] Undo differences between Z2 and Z3

2006-05-16 Thread David Pratt
There seems to be enough of a difference between Z2 and Z3 undo to have an effect on a backend like PGStorage from working on Z3. I believe the objective in the storage api is that it should not matter to the backend whether you are connected to Z2 or Z3. Can someone more familiar with the

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-16 Thread Jim Fulton
David Pratt wrote: There seems to be enough of a difference between Z2 and Z3 undo to have an effect on a backend like PGStorage from working on Z3. I believe the objective in the storage api is that it should not matter to the backend whether you are connected to Z2 or Z3. Can someone more

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-16 Thread David Pratt
Jim Fulton wrote: David Pratt wrote: There seems to be enough of a difference between Z2 and Z3 undo to have an effect on a backend like PGStorage from working on Z3. I believe the objective in the storage api is that it should not matter to the backend whether you are connected to Z2 or Z3.

Re: [ZODB-Dev] Undo differences between Z2 and Z3

2006-05-16 Thread David Pratt
Hi Jim. I managed to fix this by modifying the storage but it seems to me strange to differentiate in a storage whether it is a backend to a z2 or z3 app. Regards, David ___ For more information about ZODB, see the ZODB Wiki: