postgresql 如何查看pg_wal目录下xlog文件总大小

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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