Re: Bring to dead tuples to alive

On Tue, Jan 19, 2021, 5:03 AM Roberto Médola <tel(dot)medola(at)gmail(dot)com> wrote:

> Hi.
> I need to revert someone deletes in my table.
> I researched a lot and found pg_dirtyread and also pgtreats. Unfortunately
> I was unable to use either. My base is on a windows 2008 r2, PostgreSQL
> 9.3.5 and is over 4 TB in size. The table in question is distributed
> through tablespace in several units, inheriting to keep the records
> together.
> Fortunately for me, this base does not delete, just insert and the deletes
> that were done wrong, were executed by me.
> It turns out that I simulated on another server (linux) a table with
> fields similar to those of production and I couldn't see the dead tuples
> because of one of the fields being bytea.
> Already tried:
> - pg_dirtyread
> - compile the sources to show the HeapTupleSatisfiesVisibility
> But as the server is on windows, compilation is very complicated.
>
> Does anyone have any suggestions on how I can reverse the deletes?
>

You don't specify backup status. If you have any, even restoring them onto
a secondary machine and then locating just the records you need and
manually reentering them is better than physical restoration (in terms of
effort, risk, reliability, etc).

If your database is actively inserting new records, I'm not an expert, but
I'd be very worried that your deleted records have been physically
overwritten. I believe you need to take your DB into read-only mode to stop
inserts immediately to have much hope of recovery from physical recovery on
the production tablespaces. But hopefully someone with superior expertise
can confirm this..
Steve

>