[BUG] Cannot flush buffers of temp table deleted from other session

Hi,
Ability to do a DROP temporary table of other session leads to error :

session 1 :
create temp table test (id int);
-- let's assume that 'test' will be placed in schema 'pg_temp_0' and
has relfilepath 'base/5/t0_16390'
insert into test select generate_series(1, 1000); -- make few buffers dirty

session 2 :
drop table pg_temp_0.test; -- drop temp table of session 1

session 1:
create temp table test (id int); -- create another temp table
-- make dirty too many buffers (> temp_buffers), so postgres will try
to flush some of them
insert into test select generate_series(1, 250000);
ERROR: could not open file "base/5/t0_16390": No such file or directory

Thus, we were trying to flush buffers of an already deleted temp
table. Error occurs here : GetLocalVictimBuffer -> FlushLocalBuffer ->
smgropen(BufTagGetRelFileLocator(&bufHdr->tag), MyProcNumber).
To be honest, I don't see a good way to handle this error, because
there may be a lot of reasons why flushing failed (up to the point
that the buffer tag may be corrupted).

I attach a patch (targeted on the master branch) that contains a
sample idea of error handling - don't throw an error if we can ensure
that the relation has been deleted.
Patch contains a very rough assumption, that relation's relfilenode ==
relation's oid.

What do you think about it?

BTW, there are other bugs that can occur during interacting with other
session temp tables. I described them and suggested corrections in
this thread [1].

[1] https://www.postgresql.org/message-id/flat/CAJDiXgj72Axj0d4ojKdRWG_rnkfs4uWY414NL%3D15sCvh7-9rwg%40mail.gmail.com

--
Best regards,
Daniil Davydov