postgresql 数据库总大小与单个表大小的总和不匹配

Question

我的 postgres 数据库(版本 8.2.3)显示大小为 24 GB。

为了得到这个数字，我执行了这个查询:

SELECT
  oid, datname, pg_database_size(datname) as actualsize, 
  pg_size_pretty(pg_database_size(datname)) as size 
FROM pg_database 
ORDER BY datname  

但是，当我执行此查询时，同一数据库中各个表的大小并没有增加 24 GB:

SELECT 
  schemaname, tablename, pg_size_pretty(size) AS size_pretty, 
  pg_size_pretty(total_size) AS total_size_pretty 
FROM
  (SELECT *, pg_relation_size(schemaname||'.'||tablename) AS size, 
   pg_total_relation_size(schemaname||'.'||tablename) AS total_size 
   FROM pg_tables where schemaname = 'public') AS TABLES 
ORDER BY total_size DESC;

我已经用 pretty size 和 total_size 总结了各个表的大小，但值不匹配:

我得到了 3.5 GB 的大小

我得到 5.2 GB 的 total_size_pretty。

我在哪里可以找到剩余空间的用途？

Answer 1

通常我使用以下两个查询来获取数据库对象的大小。希望这会有所帮助。

SELECT pg_size_pretty(sum(pg_relation_size(pg_class.oid))::bigint), nspname,
CASE pg_class.relkind WHEN 'r' THEN 'table' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 'v' THEN 'view' WHEN 't' THEN 'toast' ELSE pg_class.relkind::text END
FROM pg_class
LEFT OUTER JOIN pg_namespace ON (pg_namespace.oid = pg_class.relnamespace)
GROUP BY pg_class.relkind, nspname
ORDER BY sum(pg_relation_size(pg_class.oid)) DESC;

-

SELECT pg_size_pretty(pg_relation_size(pg_class.oid)), pg_class.relname, pg_namespace.nspname,
CASE pg_class.relkind WHEN 'r' THEN 'table' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 'v' THEN 'view' WHEN 't' THEN 'TOAST' ELSE pg_class.relkind::text END
FROM pg_class 
LEFT OUTER JOIN pg_namespace ON (pg_namespace.oid = pg_class.relnamespace)
ORDER BY pg_relation_size(pg_class.oid) DESC;