如果要查询单个表的大小，可以使用常用的函数，参考语句如下：

注意：这个查询结果不包括索引大小，如果要查询索引大小，可以通过查询 information_schema.tables 来获取

如果要查询所有表的大小，包括索引，那么最方便的就是直接查询 information_schema.tables 表了，可以参考如下查询语句：

select
	table_name,
	pg_size_pretty(table_size) as table_size,
	pg_size_pretty(indexes_size) as indexes_size,
	pg_size_pretty(total_size) as total_size
from
	(
	select
		table_name,
		pg_table_size(table_name) as table_size,
		pg_indexes_size(table_name) as indexes_size,
		pg_total_relation_size(table_name) as total_size
	from
		(
		select
			('"' || table_schema || '"."' || table_name || '"') as table_name
		from
			information_schema.tables
) as all_tables
	order by
		total_size desc
) as pretty_sizes;

End~