如果你正在寻找一个总的分解，吐司和索引大小使用这个:

SELECT *, pg_size_pretty(total_bytes) AS total
, pg_size_pretty(index_bytes) AS INDEX
, pg_size_pretty(toast_bytes) AS toast
, pg_size_pretty(table_bytes) AS TABLE
FROM (
SELECT *, total_bytes-index_bytes-COALESCE(toast_bytes,0) AS table_bytes 
FROM (
  SELECT c.oid,nspname AS table_schema, relname AS TABLE_NAME
          , c.reltuples AS row_estimate
          , pg_total_relation_size(c.oid) AS total_bytes
          , pg_indexes_size(c.oid) AS index_bytes
          , pg_total_relation_size(reltoastrelid) AS toast_bytes
      FROM pg_class c
      LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
      WHERE relkind = 'r'
  ) a
) a ORDER BY total_bytes DESC;

 select uv.a tablename, pg_size_pretty(uv.b) sizepretty 
 from (select tb.tablename a, pg_table_size('schemaname.'||tb.tablename::text) b 
        from pg_tables tb 
        where tb.schemaname ilike 'schemaname' 
        order by 2 desc
       ) uv

这里的大多数答案使用pg_size_pretty，这是非常有用的，但如果你想输出一个数值，你可以自己计算

SELECT tab_size /1024 AS size_kb
      ,tab_size /1024 /1024 AS size_mb
      ,tab_size /1024 /1024 / 1024 AS size_gb
      ,tab_size /1024 /1024 / 1024 / 1024 AS size_tb
  FROM 
      (
       SELECT pg_total_relation_size(relid) AS tab_size
         FROM pg_catalog.pg_statio_user_tables
        WHERE schemaname = 'your_schema' 
          AND relname = 'your_table'
      ) AS tabs;

select table_name,n_live_tup, pg_size_pretty(pg_relation_size(table_name))
from information_schema.tables
inner join pg_stat_user_tables  on table_name=relname
where table_schema = 'public'
order by 2 desc

另一种替代方法

我需要找出哪些表占用了最多的空间。

根据其他人的回答，我使用了这个问题:

select table_name, pg_size_pretty( pg_relation_size(quote_ident(table_name)) )
from information_schema.tables
where table_schema = 'public'
order by pg_relation_size(quote_ident(table_name)) desc

得到如下结果:

table_name              pg_size_pretty
--------------------------------------
trade_binance           96 GB
closs_v2_binance_stash  46 GB
closs_bitfinex_stash    5725 MB
trade_bitfinex          5112 MB
...
api_requests            0 bytes
trade_huobi             0 bytes

我应该买个更大的固态硬盘。

我喜欢以下说法:

SELECT 
  table_name, 
  pg_size_pretty( pg_total_relation_size(quote_ident(table_name))), 
  pg_total_relation_size(quote_ident(table_name))
FROM 
  information_schema.tables
WHERE 
  table_schema = 'public'
ORDER BY 
  pg_total_relation_size(quote_ident(table_name)) DESC

你可以看到总大小在一个漂亮的格式，但它的顺序也是正确的。