我有一个 Postgres 9.2 DB，其中某个表有很多不可移动的死行：
# SELECT * FROM public.pgstattuple('mytable');
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
------------+-------------+-----------+---------------+------------------+----------------+--------------------+------------+--------------
2850512896 | 283439 | 100900882 | 3.54 | 2537195 | 2666909495 | 93.56 | 50480156 | 1.77
(1 row)
正常的吸尘也显示许多不可移动的死行：
# VACUUM VERBOSE mytable;
[...]
INFO: "mytable": found 0 removable, 2404332 nonremovable row versions in 309938 out of 316307 pages
DETAIL: 2298005 dead row versions cannot be removed yet.
There were 0 unused …