Re: block-level incremental backup

On Wed, 10 Apr 2019 11:55:51 -0700
Andres Freund <andres(at)anarazel(dot)de> wrote:

> Hi,
>
> On 2019-04-10 14:38:43 -0400, Robert Haas wrote:
> > On Wed, Apr 10, 2019 at 2:21 PM Jehan-Guillaume de Rorthais
> > <jgdr(at)dalibo(dot)com> wrote:
> > > In my current design, the scan is done backward from end to start and I
> > > keep all the records appearing after the last occurrence of their
> > > respective FPI.
> >
> > Oh, interesting. That seems like it would require pretty major
> > surgery on the WAL stream.
>
> Can't you just read each segment forward, and then reverse?

Not sure what you mean.

I first look for the very last XLOG record by jumping to the last WAL and
scanning it forward.

Then, I do a backward from there to record LSN of xlogrecord to keep.

Finally, I clone each WAL and edit them as needed (as described in my previous
email). This is my current WIP though.

> That's not that much memory?

I don't know, yet. I did not mesure it.