BUG #18112: pgstattuple of sequence failed

The following bug has been logged on the website:

Bug reference:      18112
Logged by:          Bo Chen
Email address:      bchen90@163.com
PostgreSQL version: 15.2
Operating system:   euleros
Description:        

I found pgstattuple of sequence will be failed but not PG11.x, for the code
of pgstattuple it looks like still support of sequence, but the
"rel->rd_rel->relam now is 0, not HEAP_TABLE_AM_OID", so the error report

postgres=# drop Sequence test;
DROP SEQUENCE
postgres=# create Sequence test;
CREATE SEQUENCE
postgres=# select pgstattuple('test');
ERROR:  SQLSTATE 0A000: only heap AM is supported
LOCATION:  pgstat_heap, pgstattuple.c:322
postgres=#