Re: finding changed blocks using WAL scanning

On Mon, Apr 15, 2019 at 4:31 PM Bruce Momjian <bruce@momjian.us> wrote:
> Can I throw out a simple idea?  What if, when we finish writing a WAL
> file, we create a new file 000000010000000000000001.modblock which
> lists all the heap/index files and block numbers modified in that WAL
> file?  How much does that help with the list I posted earlier?
>
>         I think there is some interesting complexity brought up in this thread.
>         Which options are going to minimize storage I/O, network I/O, have only
>         background overhead, allow parallel operation, integrate with
>         pg_basebackup.  Eventually we will need to evaluate the incremental
>         backup options against these criteria.
>
> I am thinking tools could retain modblock files along with WAL, could
> pull full-page-writes from WAL, or from PGDATA.  It avoids the need to
> scan 16MB WAL files, and the WAL files and modblock files could be
> expired independently.

That is pretty much exactly what I was intending to propose.

-- 
Robert Haas
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