ignore_system_indexes=on no help for missing/corrupt pg_class_oid_index?

Greetings admins!

I found that the ignore_system_indexes flag apparently doesn't get me
past this case of a corrupt index as seen below.

Or am I doing something silly here?

The particular DB is a scratch so we'll just drop it but anyway,
comments?

I've not had to resort to this anytime lately but IIRC the
ignore_system_indexes foo did the expected for us $sometime before.

I believe that index 2662::regclass is probably this one but of course I
had to probe for it in some other DB. The same one exists in template1
and I presume all other DBS as well.

Please advise. Thx!

----

$ pg --single -D $PWD -c config_file=$cf -c hba_file=$hba -P broken_db
,,,,1969183,2023-08-08 22:25:17.844 GMT,,XX000,64d2c0cd.1e0c1f,1,2023-08-08 22:25:17 GMT,1/1,0 || PANIC: could not open critical system index 2662
Aborted

$ pg --single -D $PWD -c config_file=$cf -c hba_file=$hba -P postgres
,,,,1969691,2023-08-08 22:25:51.027 GMT,,00000,64d2c0ee.1e0e1b,1,2023-08-08 22:25:50 GMT,1/0,0 || LOG: database system was interrupted; last known up at 2023-08-08 22:25:17 GMT
,,,,1969691,2023-08-08 22:25:51.045 GMT,,00000,64d2c0ee.1e0e1b,2,2023-08-08 22:25:50 GMT,1/0,0 || LOG: database system was not properly shut down; automatic recovery in progress
,,,,1969691,2023-08-08 22:25:51.048 GMT,,00000,64d2c0ee.1e0e1b,3,2023-08-08 22:25:50 GMT,1/0,0 || LOG: invalid record length at 0/5F175310: wanted 24, got 0
,,,,1969691,2023-08-08 22:25:51.048 GMT,,00000,64d2c0ee.1e0e1b,4,2023-08-08 22:25:50 GMT,1/0,0 || LOG: redo is not required
,,,,1969691,2023-08-08 22:25:51.055 GMT,,00000,64d2c0ee.1e0e1b,5,2023-08-08 22:25:50 GMT,1/0,0 || LOG: checkpoint starting: end-of-recovery immediate wait
,,,,1969691,2023-08-08 22:25:51.063 GMT,,00000,64d2c0ee.1e0e1b,6,2023-08-08 22:25:50 GMT,1/0,0 || LOG: checkpoint complete: wrote 3 buffers (0.0%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.004 s, sync=0.001 s, total=0.010 s; sync files=2, longest=0.001 s, average=0.001 s; distance=0 kB, estimate=0 kB

PostgreSQL stand-alone backend 15.3 (Ubuntu 15.3-1.pgdg20.04+1)
backend> select relname from pg_class where oid=2662;
,,,,1969691,2023-08-08 22:26:11.183 GMT,,01000,64d2c0ee.1e0e1b,7,2023-08-08 22:25:50 GMT,1/2,0 || WARNING: using index "pg_toast_2619_index" despite IgnoreSystemIndexes
1: relname (typeid = 19, len = 64, typmod = -1, byval = f)
----
1: relname = "pg_class_oid_index" (typeid = 19, len = 64, typmod = -1, byval = f)
----
backend> select version()
1: version (typeid = 25, len = -1, typmod = -1, byval = f)
----
1: version = "PostgreSQL 15.3 (Ubuntu 15.3-1.pgdg20.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0, 64-bit" (typeid = 25, len = -1, typmod = -1, byval = f)
----
backend> show ignore_system_indexes
1: ignore_system_indexes (typeid = 25, len = -1, typmod = -1, byval = f)
----
1: ignore_system_indexes = "on" (typeid = 25, len = -1, typmod = -1, byval = f)
----
backend>