当然如果你登录服务器所在主机，直接在$pgdat/pg_wal下执行：
du -h --max-depth=1 ./
可以得到。
#du -h --max-depth=1 ./ 4.0k ./archive_status 193m ./
如果通过客户端怎么做呢？
答案：pg_ls_waldir()函数。pg_ls_waldir()是pg 10.0引入的函数，可以输出数据库wal目录的所有文件。
postgres=# select sum(size) from pg_ls_waldir(); sum ----------- 201326592 (1 row)
单位是byte，所以当前pg_wal的xlog日志总大小为201326592/1024/1024=192m。
也可以使用：
postgres=# select count(*) from pg_ls_waldir(); count ------- 12 (1 row)
12表示wal日志文件个数，总大小12*16=192m。
16表示单个wal日志文件大小，单位mb，wal 日志文件大小默认为16mb。
bonus：
1、怎么调整单个wal日志文件大小？
答：使用 initdb 调整wal文件大小。
2、pg_ls_logdir() 也是pg10.0版本引入的函数，输出数据库日志目录的所有文件。
postgres=# select * from pg_ls_logdir();
name | size | modification
----------------------------------+---------+------------------------
postgresql-2020-04-28_092020.log | 2277343 | 2020-04-29 11:34:56+08
postgresql-2020-04-28_092020.csv | 140050 | 2020-04-29 11:34:56+08
3、如何列出/data文件夹中的文件？
答：pg_ls_dir
postgres=# select pg_ls_dir('/data');
pg_ls_dir
----------------------
补充：postgresql 查看wal生成频率和大小
–wal 文件生成数量
–linux ls –full-time stat filename
–pg_stat_file返回一个记录，其中包含
– 1 size 文件尺寸
– 2 access 最后访问时间戳(linux:最近访问) 、
– 3 modification 最后修改时间戳(linux:最近更改–) 、
– 4 change 最后文件状态改变时间戳（只支持 unix 平台）(linux:最近改动) 、
– 5 creation 文件创建时间戳（只支持 windows）
– 6 isdir 一个boolean指示它是否为目录 isdir
– select * from pg_stat_file('/var/lib/postgresql/9.1/main/pg_xlog/0000000200000bbb000000a9');
– /var/lib/postgresql/9.1/main/pg_xlog
– /var/log/postgresql
– /mnt/nas_dbbackup/archivelog
with tmp_file as (
select t1.file,
t1.file_ls,
(pg_stat_file(t1.file)).size as size,
(pg_stat_file(t1.file)).access as access,
(pg_stat_file(t1.file)).modification as last_update_time,
(pg_stat_file(t1.file)).change as change,
(pg_stat_file(t1.file)).creation as creation,
(pg_stat_file(t1.file)).isdir as isdir
from (select dir||'/'||pg_ls_dir(t0.dir) as file,
pg_ls_dir(t0.dir) as file_ls
from ( select '/var/lib/postgresql/9.1/main/pg_xlog'::text as dir
--需要修改这个物理路径
--select '/mnt/nas_dbbackup/archivelog'::text as dir
--select setting as dir from pg_settings where name='log_directory'
) t0
) t1
where 1=1
order by (pg_stat_file(file)).modification desc
)
select to_char(date_trunc('day',tf0.last_update_time),'yyyymmdd') as day_id,
sum(case when date_part('hour',tf0.last_update_time) >=0 and date_part('hour',tf0.last_update_time) <24 then 1 else 0 end) as wal_num_all,
sum(case when date_part('hour',tf0.last_update_time) >=0 and date_part('hour',tf0.last_update_time) <1 then 1 else 0 end) as wal_num_00_01,
sum(case when date_part('hour',tf0.last_update_time) >=1 and date_part('hour',tf0.last_update_time) <2 then 1 else 0 end) as wal_num_01_02,
sum(case when date_part('hour',tf0.last_update_time) >=2 and date_part('hour',tf0.last_update_time) <3 then 1 else 0 end) as wal_num_02_03,
sum(case when date_part('hour',tf0.last_update_time) >=3 and date_part('hour',tf0.last_update_time) <4 then 1 else 0 end) as wal_num_03_04,
sum(case when date_part('hour',tf0.last_update_time) >=4 and date_part('hour',tf0.last_update_time) <5 then 1 else 0 end) as wal_num_04_05,
sum(case when date_part('hour',tf0.last_update_time) >=5 and date_part('hour',tf0.last_update_time) <6 then 1 else 0 end) as wal_num_05_06,
sum(case when date_part('hour',tf0.last_update_time) >=6 and date_part('hour',tf0.last_update_time) <7 then 1 else 0 end) as wal_num_06_07,
sum(case when date_part('hour',tf0.last_update_time) >=7 and date_part('hour',tf0.last_update_time) <8 then 1 else 0 end) as wal_num_07_08,
sum(case when date_part('hour',tf0.last_update_time) >=8 and date_part('hour',tf0.last_update_time) <9 then 1 else 0 end) as wal_num_08_09,
sum(case when date_part('hour',tf0.last_update_time) >=9 and date_part('hour',tf0.last_update_time) <10 then 1 else 0 end) as wal_num_09_10,
sum(case when date_part('hour',tf0.last_update_time) >=10 and date_part('hour',tf0.last_update_time) <11 then 1 else 0 end) as wal_num_10_11,
sum(case when date_part('hour',tf0.last_update_time) >=11 and date_part('hour',tf0.last_update_time) <12 then 1 else 0 end) as wal_num_11_12,
sum(case when date_part('hour',tf0.last_update_time) >=12 and date_part('hour',tf0.last_update_time) <13 then 1 else 0 end) as wal_num_12_13,
sum(case when date_part('hour',tf0.last_update_time) >=13 and date_part('hour',tf0.last_update_time) <14 then 1 else 0 end) as wal_num_13_14,
sum(case when date_part('hour',tf0.last_update_time) >=14 and date_part('hour',tf0.last_update_time) <15 then 1 else 0 end) as wal_num_14_15,
sum(case when date_part('hour',tf0.last_update_time) >=15 and date_part('hour',tf0.last_update_time) <16 then 1 else 0 end) as wal_num_15_16,
sum(case when date_part('hour',tf0.last_update_time) >=16 and date_part('hour',tf0.last_update_time) <17 then 1 else 0 end) as wal_num_16_17,
sum(case when date_part('hour',tf0.last_update_time) >=17 and date_part('hour',tf0.last_update_time) <18 then 1 else 0 end) as wal_num_17_18,
sum(case when date_part('hour',tf0.last_update_time) >=18 and date_part('hour',tf0.last_update_time) <19 then 1 else 0 end) as wal_num_18_19,
sum(case when date_part('hour',tf0.last_update_time) >=19 and date_part('hour',tf0.last_update_time) <20 then 1 else 0 end) as wal_num_19_20,
sum(case when date_part('hour',tf0.last_update_time) >=20 and date_part('hour',tf0.last_update_time) <21 then 1 else 0 end) as wal_num_20_21,
sum(case when date_part('hour',tf0.last_update_time) >=21 and date_part('hour',tf0.last_update_time) <22 then 1 else 0 end) as wal_num_21_22,
sum(case when date_part('hour',tf0.last_update_time) >=22 and date_part('hour',tf0.last_update_time) <23 then 1 else 0 end) as wal_num_22_23,
sum(case when date_part('hour',tf0.last_update_time) >=23 and date_part('hour',tf0.last_update_time) <24 then 1 else 0 end) as wal_num_23_24
from tmp_file tf0
where 1=1
and tf0.file_ls not in ('archive_status')
group by to_char(date_trunc('day',tf0.last_update_time),'yyyymmdd')
order by to_char(date_trunc('day',tf0.last_update_time),'yyyymmdd') desc
;
以上为个人经验，希望能给大家一个参考，也希望大家多多支持www.887551.com。如有错误或未考虑完全的地方，望不吝赐教。