postgres之清理空间碎片

postgres=#  select * from pg_stat_user_tables where relname = 'test';
-[ RECORD 1 ]-------+------------------------------
relid               | 23400
schemaname          | public
relname             | test
seq_scan            | 12
seq_tup_read        | 49290
idx_scan            |
idx_tup_fetch       |
n_tup_ins           | 22916
n_tup_upd           | 25249
n_tup_del           | 0
n_tup_hot_upd       | 0
n_live_tup          | 22916
n_dead_tup          | 2333
n_mod_since_analyze | 0
last_vacuum         |
last_autovacuum     | 2019-10-09 09:15:52.549356+08
last_analyze        |
last_autoanalyze    | 2019-10-09 09:15:55.279256+08
vacuum_count        | 0
autovacuum_count    | 1
analyze_count       | 0
autoanalyze_count   | 2

postgres=# vacuum landing_person_cdl_02;  #执行手工的清理
VACUUM
postgres=#  select * from pg_stat_user_tables where relname = 'landing_person_cdl_02'; #查看清理结果
-[ RECORD 1 ]-------+------------------------------
relid               | 23400
schemaname          | public
relname             | landing_person_cdl_02
seq_scan            | 12
seq_tup_read        | 49290
idx_scan            |
idx_tup_fetch       |
n_tup_ins           | 22916
n_tup_upd           | 25249
n_tup_del           | 0
n_tup_hot_upd       | 0
n_live_tup          | 21923
n_dead_tup          | 0
n_mod_since_analyze | 0
last_vacuum         | 2019-10-10 09:57:09.651626+08
last_autovacuum     | 2019-10-09 09:15:52.549356+08
last_analyze        |
last_autoanalyze    | 2019-10-09 09:15:55.279256+08
vacuum_count        | 1
autovacuum_count    | 1
analyze_count       | 0
autoanalyze_count   | 2

说明

n_live_tup的数量是当前表的数据量。
n_dead_tup的数据量是未回收的空间。

查看表的大小

select pg_size_pretty(pg_relation_size('test'));