Re: "PANIC: could not open critical system index 2662" - twice

On Wed, May 10, 2023 at 9:32 AM Evgeny Morozov <
postgresql3@realityexists.net> wrote:

> On 10/05/2023 6:39 am, Kirk Wolak wrote:
>
> It could be as simple as creating temp tables in the other database (since
> I believe pg_class was hit).
>
> We do indeed create temp tables, both in other databases and in the ones
> being tested. (We also create non-temp tables there.)
>
>
> Also, not sure if the OP has a set of things done after he creates the DB
> that may help?
>
> Basically we read rows from the source database, create some partitions of
> tables in the target database, insert into a temp table there using BULK
> COPY, then using a regular INSERT copy from the temp tables to the new
> partitions.
>
>
> Now that the probem has been reproduced and understood by the PG
> developers, could anyone explain why PG crashed entirely with the "PANIC"
> error back in April when only specific databases were corrupted, not any
> global objects necesary for PG to run? And why did it not crash with the
> "PANIC" on this occasion?
>
I understand the question as:
Why would it PANIC on non-system data corruption, but not on system data
corruption?

To which my guess is:
Because System  Data Corruption, on startup is probably a use case, and we
want to report, and come up as much as possible.
Whereas the OTHER code did a PANIC simply because it was BOTH unexpected,
and NOT Where it was in a place it could move forward.
Meaning it had no idea if it read in bad data, or if it CREATED the bad
data.

As a programmer, you will find much more robust code on startup checking
than in the middle of doing something else.

But just a guess.  Someone deeper into the code might explain it better.
And you COULD go dig through the source to compare the origination of the
error messages?

Kirk...