From: | Fabrice Chapuis <fabrice636861(at)gmail(dot)com> |
---|---|
To: | Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: pg_waldump |
Date: | 2023-12-19 15:11:54 |
Message-ID: | CAA5-nLCQKXCiHpNCF23YjtWGYH5FPHCP3rvTOVo2iR_ifcpOEg@mail.gmail.com |
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Lists: | pgsql-hackers |
Ok thanks for all these precisions
Regards
Fabrice
On Tue, Dec 19, 2023 at 2:00 PM Matthias van de Meent <
boekewurm+postgres(at)gmail(dot)com> wrote:
> On Tue, 19 Dec 2023, 12:27 Fabrice Chapuis, <fabrice636861(at)gmail(dot)com>
> wrote:
> >
> > Hi,
> > Is it possible to visualize the DDL with the pg_waldump tool. I created
> a postgres user but I cannot find the creation command in the wals
>
> Not really, no. PostgreSQL does not log DDL or DML as such in WAL.
> Essentially all catalog updates are logged only as changes on a
> certain page in some file: a new user getting inserted would be
> approximately "Insert tuple [user's pg_role row data] on page X in
> file [the file corresponding to the pg_role table]".
>
> You could likely derive most DDL commands from Heap/Insert,
> Heap/Delete, and Heap/Update records (after cross-referencing the
> database's relfilemap), as most DDL is "just" a lot of in-memory
> operations plus some record insertions/updates/deletes in catalog
> tables. You'd also need to keep track of any relfilemap changes while
> processing the WAL, as VACUUM FULL on the catalog tables would change
> the file numbering of catalog tables...
>
> Kind regards,
>
> Matthias van de Meent
> Neon (https://neon.tech)
>
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