Re: Undo logs

On Wed, Nov 14, 2018 at 2:42 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Sat, Nov 10, 2018 at 9:27 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Mon, Nov 5, 2018 at 5:10 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> > >
> > [review for undo record layer (0003-undo-interface-v3)]
> >
> > I might sound repeating myself, but just to be clear, I was involved
> > in the design of this patch as well and I have given a few high-level
> > inputs for this patch. I have used this interface in the zheap
> > development, but haven't done any sort of detailed review which I am
> > doing now. I encourage others also to review this patch.
>
> Thanks for the review, please find my reply inline.
> >
> > 1.
> > * NOTES:
> > + * Handling multilog -
> > + * It is possible that the undo record of a transaction can be spread across
> > + * multiple undo log. And, we need some special handling while inserting the
> > + * undo for discard and rollback to work sanely.
> >
> > I think before describing how the undo record is spread across
> > multiple logs, you can explain how it is laid out when that is not the
> > case. You can also explain how undo record headers are linked. I am
> > not sure file header is the best place or it should be mentioned in
> > README, but I think for now we can use file header for this purpose
> > and later we can move it to README if required.
> Added in the header.
>
> >
> > 2.
> > +/*
> > + * FIXME: Do we want to support undo tuple size which is more than the BLCKSZ
> > + * if not than undo record can spread across 2 buffers at the max.
> > + */
> >
> > +#define MAX_BUFFER_PER_UNDO 2
> >
> > I think here the right question is what is the possibility of undo
> > record to be greater than BLCKSZ? For zheap, as of today, we don'
> > have any such requirement as the largest undo record is written for
> > update or multi_insert and in both cases we don't exceed the limit of
> > BLCKSZ. I guess some user other than zheap could probably have such
> > requirement and I don't think it is impossible to enhance this if we
> > have any requirement.
> >
> > If anybody else has an opinion here, please feel to share it.
>
> Should we remove this FIXME or lets wait for some other opinion. As
> of now I have kept it as it is.
> >

I think you can keep it with XXX instead of Fixme as there is nothing to fix.

Both the patches 0003-undo-interface-v4.patch and
0004-undo-interface-test-v4.patch appears to be same except for the
name?

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com