PostgreSQL 查询所有数据库大小，表大小，索引大小，以及表空间大小

1. 查询数据库大小

-- 查询单个数据库大小
select pg_size_pretty(pg_database_size('postgres')) as size;

-- 查询所有数据库大小
select datname, pg_size_pretty (pg_database_size(datname)) AS size from pg_database; 

2. 查询表大小

-- 查询单个表大小
select pg_size_pretty(pg_relation_size('mytab')) as size;

-- 查询所有表大小
select relname, pg_size_pretty(pg_relation_size(relid)) as size from pg_stat_user_tables;

-- 查询单个表的总大小，包括该表的索引大小
select pg_size_pretty(pg_total_relation_size('tab')) as size;

-- 查询所有表的总大小，包括其索引大小
select relname, pg_size_pretty(pg_total_relation_size(relid)) as size from pg_stat_user_tables;

3. 查询索引大小（暂时没有一次性查询所有索引大小的函数）

-- 查询单个索引大小
select pg_size_pretty(pg_relation_size('myindex')) as size;

4. 查询表空间大小

-- 查询单个表空间大小
select pg_size_pretty(pg_tablespace_size('pg_default')) as size;

-- 查询所有表空间大小
select spcname, pg_size_pretty(pg_tablespace_size(spcname)) as size from pg_tablespace;
-- 或
select spcname, pg_size_pretty(pg_tablespace_size(oid)) as size from pg_tablespace;

来源：https://blog.csdn.net/u013992330/article/details/106807311