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 ;
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