Julian Foad <julianf...@gmail.com> writes: > Stepping back a little, I want to pose the rhetorical question: Who is > to say which FS layer implementation is the wrong one? BDB is the > earlier implementation. If we define correctness by precedent, then > it's the FSFS behaviour that we should consider to be wrong. On the > other hand, if we define correctness by specification, then we need to > specify this behaviour somewhere, not just "randomly" change it.
We could leave it unspecified, or explicitly specify that the backend has a choice. > So let's try to enumerate the issues. > > (1) In FS-BDB, a no-op commit may or may not produce a new root > node-rev (depending on the specific form of the commit), whereas in > FSFS, every commit produces a new root node-rev. > > (2) FS-BDB reports a different result from svn_fs_txn_base_revision() > before and after reloading by name, when the no-new-node-rev situation > in (1) occurs. > > (3) A recently added check can reject valid delete operations when (1) > and (2) occur. I'd say the check relies on (2). The check is not explicitly assuming anything about the root nodes. It is a backend bug that BDB uses the root node as a proxy for the base revision and causes the bug. > Which of those are bugs, which are acceptable, which need to stay as > they for backward compatibility even if they are bugs, and so on? > > It seems to me that (2) is definitely a bug, but I'm not sure about > (1) and therefore not sure about (3). (2) is a bug. We fix it by making BDB always make a new root node. > Daniel Shahaf wrote on 27 Nov: >> Can the problem happen on nodes other than the root? I haven't tried >> it, but I wonder if a open_root/open_directory/close_directory/close_edit >> editor drive might lead to an instance of this problem on the directory >> that was opened and closed without modification. > > Yes, that's an important question too. In other words, what semantics > do we want for a "no-op change" in general, within a commit? > > And is it possible to make a commit which starts with opening (as the > root of the commit) a directory that is not the root of the > repository, and if so, what about that case? I don't think that is relevant. This about the FS API so the calls are begin_txn and commit_txn. -- Philip Martin WANdisco
