[ZODB-Dev] Removing version support

[Jim Fulton]

I plan to remove version support from ZODB.  Here's my plan:

- In 3.8, we'll still have the version support we have now, bugs and  
all. We will try not to add new bugs, but we won't necessarily fix  
old ones.  New APIs, if any, introduced in 3.8 won't support  
versions, but won't break  them.

- We will be free, after 3.8, to rip out version support as we have  
time.  When we begin this:

    - We need to first remove the APIs that allow versions to be  
created.

    - We need to have plans for dealing with databases that contain  
version data.  For example, database iterators need to skip over  
version data, or we need database conversion tools that remove  
version data.

Unfortunately, I expect we'll be saddled with remnants for some time,  
as many APIs that are not version specific have version-related  
arguments and return values.  Also, and related, I don't want to  
break the current ZEO protocol.  I find it very useful that current  
ZEO servers work with fairly old clients (back to 3.2).  (I have a  
Zope 2.6 site that is using a current ZEO server.) Eventually, I hope  
we will create new version-free APIs.

Jim

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