1. 在数据库中查单个表 

select pg_size_pretty(pg_relation_size('table_name'));

2. 查出并按大小排序

SELECT table_schema || '.' || table_name AS table_full_name, pg_size_pretty(pg_total_relation_size('"' || table_schema || '"."' || table_name || '"')) AS sizeFROM information_schema.tablesORDER BY pg_total_relation_size('"' || table_schema || '"."' || table_name || '"') DESC limit 20

3. 查出表大小按大小排序并分离data与index

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_sizeFROM (    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