Re: block-level incremental backup - Mailing list pgsql-hackers

From Jehan-Guillaume de Rorthais
Subject Re: block-level incremental backup
Date
Msg-id 20190410225418.030d47b6@firost
Whole thread Raw
In response to Re: block-level incremental backup  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
On Wed, 10 Apr 2019 11:55:51 -0700
Andres Freund <andres@anarazel.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@dalibo.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.



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