pg_table_size，pg_relation_size&之间有什么区别？ pg_total_relation_size？ （PostgreSQL） [英] What's the difference between pg_table_size, pg_relation_size & pg_total_relation_size? (PostgreSQL)

问题描述

pg_table_size（）， pg_relation_size（）和&的区别是什么？ pg_total_relation_size（）？

我理解文档中的，但这意味着我的表实际有多少空间

解决方案

对于随机表：

 ＃选择pg_relation_size（20306，'main'）作为main，
 pg_relation_size（20306，'fsm'）作为fsm，
 pg_relation_size（20306，'vm'）作为vm，
 pg_relation_size（20306，'init'）作为init，
 pg_table_size（20306），pg_indexes_size（20306）作为索引，
 pg_total_relation_size（20306）作为总索引; 
主要| fsm | vm |初始化| pg_table_size |索引|总计
 -------- + ------- + ------ + ------ + -------------- -+ --------- + -------- 
 253952 | 24576 | 8192 | 0 | 286720 | 196608 | 483328 
（1行）
  

从中可以看出 pg_table_size 是 pg_relation_size 的所有返回值的总和。 pg_total_relation_size 是 pg_table_size 和 pg_indexes_size 的总和。 / p>

如果您想知道表正在使用多少空间，请使用 pg_table_size 和 pg_total_relation_size 考虑一下-一个数字仅表形式，一个数字是表+索引。

选中存储文件布局以获取有关 fsm ， vm 和 init 的含义以及它们在磁盘上的存储方式。

What's the difference between pg_table_size(), pg_relation_size() & pg_total_relation_size()?

I understand the basic differences explained in the documentation, but what does it imply in terms of how much space my table is actually using?

解决方案

For a random table:

# select pg_relation_size(20306, 'main') as main,
  pg_relation_size(20306, 'fsm') as fsm,
  pg_relation_size(20306, 'vm') as vm,
  pg_relation_size(20306, 'init') as init,
  pg_table_size(20306), pg_indexes_size(20306) as indexes,
  pg_total_relation_size(20306) as total;
  main  |  fsm  |  vm  | init | pg_table_size | indexes |  total 
--------+-------+------+------+---------------+---------+--------
 253952 | 24576 | 8192 |    0 |        286720 |  196608 | 483328
(1 row)

From that, you can tell pg_table_size is the sum of all the return values of pg_relation_size. And pg_total_relation_size is the sum of pg_table_size and pg_indexes_size.

If you want to know how much space your tables are using, use pg_table_size and pg_total_relation_size to think about them -- one number is table-only, and one number is table + indexes.

Check the storage file layout for some info about what fsm, vm, and init mean, and how they're stored on disk.

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