3中方式，任何一个都行

第一 在数据库中查单个表

select pg_size_pretty(pg_relation_size('table_name'));

第二 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 size FROM information_schema.tables ORDER BY pg_total_relation_size('"' || table_schema || '"."' || table_name || '"') DESC limit 20

第三 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_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