您可以使用下面的查询来查找PostgreSQL所有数据库的大小。

参考资料来自这个博客。

SELECT 
    datname AS DatabaseName
    ,pg_catalog.pg_get_userbyid(datdba) AS OwnerName
    ,CASE 
        WHEN pg_catalog.has_database_privilege(datname, 'CONNECT')
        THEN pg_catalog.pg_size_pretty(pg_catalog.pg_database_size(datname))
        ELSE 'No Access For You'
    END AS DatabaseSize
FROM pg_catalog.pg_database
ORDER BY 
    CASE 
        WHEN pg_catalog.has_database_privilege(datname, 'CONNECT')
        THEN pg_catalog.pg_database_size(datname)
        ELSE NULL
    END DESC;

来自PostgreSQL wiki。

注意:用户无法连接到的数据库按无限大小排序。

SELECT d.datname AS Name,  pg_catalog.pg_get_userbyid(d.datdba) AS Owner,
    CASE WHEN pg_catalog.has_database_privilege(d.datname, 'CONNECT')
        THEN pg_catalog.pg_size_pretty(pg_catalog.pg_database_size(d.datname))
        ELSE 'No Access'
    END AS Size
FROM pg_catalog.pg_database d
    ORDER BY
    CASE WHEN pg_catalog.has_database_privilege(d.datname, 'CONNECT')
        THEN pg_catalog.pg_database_size(d.datname)
        ELSE NULL
    END DESC -- nulls first
    LIMIT 20

该页面还提供了用于查找最大关系和最大表大小的代码片段。

根据@Hendy Irawan的回答

显示数据库大小:

\l+

e.g.

=> \l+
 berbatik_prd_commerce    | berbatik_prd     | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 19 MB   | pg_default | 
 berbatik_stg_commerce    | berbatik_stg     | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 8633 kB | pg_default | 
 bursasajadah_prd         | bursasajadah_prd | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                       | 1122 MB | pg_default | 

显示表大小:

\d+

e.g.

=> \d+
 public | tuneeca_prd | table | tomcat | 8192 bytes | 
 public | tuneeca_stg | table | tomcat | 1464 kB    | 

只适用于psql。

-- Database Size
SELECT pg_size_pretty(pg_database_size('Database Name'));
-- Table Size
SELECT pg_size_pretty(pg_relation_size('table_name'));

您可以从“pg_database”系统表中获得可以连接到的所有数据库的名称。只需将函数应用于名称，如下所示。

select t1.datname AS db_name,  
       pg_size_pretty(pg_database_size(t1.datname)) as db_size
from pg_database t1
order by pg_database_size(t1.datname) desc;

如果您想让机器而不是人使用输出，则可以删除pg_size_pretty()函数。

du -k /var/lib/postgresql/ |sort -n |tail