Thanks for raizing this up, Robert and the comment, Andres. At Tue, 13 Sep 2022 07:00:42 +0530, Dilip Kumar <dilipbal...@gmail.com> wrote in > On Tue, Sep 13, 2022 at 3:22 AM Andres Freund <and...@anarazel.de> wrote: > > > > > It's not obvious to me that it's the right design (or even correct) to ask > > reorderbuffer about an xid being a subxid. Maybe I'm missing something, but > > why would reorderbuffer even be guaranteed to know about all these subxids? > > Yeah, you are right, the reorderbuffer will only know about the > transaction for which changes got added to the reorder buffer. So > this seems not to be the right design idea.
That function is called after the SnapBuild reaches SNAPBUILD_CONSISTENT state ,or SnapBuildInitialSnapshot() rejects other than that state. That is, IIUC the top-sub relationship of all the currently running transactions is fully known to reorder buffer. We need a comment about that. > > I wonder if a better fix here wouldn't be to allow importing a snapshot > > with a > > larger ->xid array. Yes, we can't do that in CurrentSnapshotData, but IIRC > > we > > need to be in a transactional snapshot anyway, which is copied anyway? > > Yeah when I first found this issue, I thought that should be the > solution. But later it went in a different direction. I think that that is the best solution if rbtxn_is_known_subxzact() is known to be unreliable at the time. regards. -- Kyotaro Horiguchi NTT Open Source Software Center
