Re: Reorderbuffer crash during recovery

On Tue, Dec 17, 2019 at 2:32 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Dec 11, 2019 at 11:13 AM vignesh C <vignesh21@gmail.com> wrote:
> >
> >
> > It sets the final_lsn here so that it can iterate from the start_lsn
> > to final_lsn and cleanup the serialized files in
> > ReorderBufferRestoreCleanup function. One solution We were thinking
> > was to store the lsn of the last serialized change while serialiizing
> > and set the final_lsn in the above case where it crashes like the
> > below code:
>
> Sure, we can do something on the lines what you are suggesting, but
> why can't we update final_lsn at the time of serializing the changes?
> If we do that then we don't even need to compute it separately during
> ReorderBufferAbortOld.
>
> Let me try to explain the problem and proposed solutions for the same.
> Currently, after serializing the changes we remove the 'changes' from
> ReorderBufferTXN.  Now, if the system crashes due to any reason after
> that, we won't be able to compute final_lsn after the restart.  And
> that leads to access violation in ReorderBufferAbortOld which is
> trying to access changes list from ReorderBufferTXN to compute
> final_lsn.
>
> We could fix it by either tracking 'last_serialized_change' as
> proposed by Vignesh or we could update the final_lsn while we
> serialize the changes.
>

I felt amit solution also solves the problem. Attached patch has the
fix based on the solution proposed.
Thoughts?

Regards,
Vignesh
EnterpriseDB: http://www.enterprisedb.com