__no_side_effects__, was Re: [ZODB-Dev] Re: [Zodb-checkins] SVN: ZODB/branches/3.4/

[Shane Hathaway]

Tim Peters wrote:
> What I seem to be missing entirely here is why Zope ships Prefix instances
> at the base ZEO msg level to begin with; maybe it's to call some method I
> misunderstand (or haven't even bumped into yet <0.6 wink>).

When you want to undo something, Zope asks the ZEO server for a list of
undoable transactions.  The resulting list should include only the
transactions the user is allowed to undo, so Zope passes an object that
implements __cmp__ to the ZEO server.  The object is used to filter
transactions by the transaction's request path.  ZopeUndo.Prefix is one
such filter.

However, to my knowledge, there are no alternative filters. :-(

Shane