heap_force_kill 将 “已使用” 行指针标记为 “已删除”，而不检查元组。此函数的预期用途是强制删除其他方式无法访问的元组。例如

test=> select * from t1 where ctid = '(0, 1)';
ERROR:  could not access status of transaction 4007513275
DETAIL:  Could not open file "pg_xact/0EED": No such file or directory.

test=# select heap_force_kill('t1'::regclass, ARRAY['(0, 1)']::tid[]);
 heap_force_kill
-----------------

(1 row)

test=# select * from t1 where ctid = '(0, 1)';
(0 rows)

heap_force_freeze 将元组标记为冻结，而不检查元组数据。此函数的预期用途是使由于损坏的可见性信息而无法访问的元组变得可访问，或者由于损坏的可见性信息而阻止表成功 vacuum 的元组。例如

test=> vacuum t1;
ERROR:  found xmin 507 from before relfrozenxid 515
CONTEXT:  while scanning block 0 of relation "public.t1"

test=# select ctid from t1 where xmin = 507;
 ctid
-------
 (0,3)
(1 row)

test=# select heap_force_freeze('t1'::regclass, ARRAY['(0, 3)']::tid[]);
 heap_force_freeze
-------------------

(1 row)

test=# select ctid from t1 where xmin = 2;
 ctid
-------
 (0,3)
(1 row)