一、简介
PostgreSQL 提供了多个系统管理函数来查看表，索引，表空间及数据库的大小，下面详细介绍一下。
二、数据库对象尺寸函数
| 函数名 | 返回类型 | 描述 |
| pg_column_size(any) | int | 存储一个指定的数值需要的字节数（可能压缩过） |
| pg_database_size(oid) | bigint | 指定OID的数据库使用的磁盘空间 |
| pg_database_size(name) | bigint | 指定名称的数据库使用的磁盘空间 |
| pg_indexes_size(regclass) | bigint | 关联指定表OID或表名的表索引的使用总磁盘空间 |
| pg_relation_size(relation regclass, fork text) | bigint | 指定OID或名的表或索引，通过指定fork('main', 'fsm' 或'vm')所使用的磁盘空间 |
| pg_relation_size(relation regclass) | bigint | pg_relation_size(..., 'main')的缩写 |
| pg_size_pretty(bigint) | text | Converts a size in bytes expressed as a 64-bit integer into a human-readable format with size units |
| pg_size_pretty(numeric) | text | 把以字节计算的数值转换成一个人类易读的尺寸单位 |
| pg_table_size(regclass) | bigint | 指定表OID或表名的表使用的磁盘空间，除去索引（但是包含TOAST，自由空间映射和可视映射） |
| pg_tablespace_size(oid) | bigint | 指定OID的表空间使用的磁盘空间 |
| pg_tablespace_size(name) | bigint | 指定名称的表空间使用的磁盘空间 |
| pg_total_relation_size(regclass) | bigint | 指定表OID或表名使用的总磁盘空间，包括所有索引和TOAST数据 |
三、实例讲解
3.1 查看存储一个指定的数值需要的字节数
david=# select pg_column_size(1);
pg_column_size
----------------
4
(1 row)
david=# select pg_column_size(10000);
pg_column_size
----------------
4
(1 row)
david=# select pg_column_size('david');
pg_column_size
----------------
6
(1 row)
david=# select pg_column_size('hello,world');
pg_column_size
----------------
12
(1 row)
david=# select pg_column_size('2013-04-18 15:17:21.622885+08');
pg_column_size
----------------
30
(1 row)
david=# select pg_column_size('中国');
pg_column_size
----------------
7
(1 row)
david=#
3.2 查看数据库大小
查看原始数据
david=# \d test
Table "public.test"
Column | Type | Modifiers
-----------+-----------------------+-----------
id | integer |
name | character varying(20) |
gender | boolean |
join_date | date |
dept | character(4) |
Indexes:
"idx_join_date_test" btree (join_date)
"idx_test" btree (id)
david=# select count(1) from test;
count
---------
1835008
(1 row)
david=#
查看david 数据库大小
david=# select pg_database_size('david');
pg_database_size
------------------
190534776
(1 row)
david=#
查看所有数据库大小
david=# select pg_database.datname, pg_database_size(pg_database.datname) AS size from pg_database; datname | size -----------+------------- template0 | 6513156 postgres | 6657144 jboss | 6521348 bugs | 6521348 david | 190534776 BMCV3 | 28147135608 mydb | 10990712 template1 | 6521348 (8 rows) david=#
这样查出来的结果，看上去太长了，不太容易读数。
3.3 以人性化的方式显示大小
david=# select pg_size_pretty(pg_database_size('david'));
pg_size_pretty
----------------
182 MB
(1 row)
david=#
3.4 查看单索引大小
david=# select pg_relation_size('idx_test');
pg_relation_size
------------------
41238528
(1 row)
david=# select pg_size_pretty(pg_relation_size('idx_test'));
pg_size_pretty
----------------
39 MB
(1 row)
david=#
david=# select pg_size_pretty(pg_relation_size('idx_join_date_test'));
pg_size_pretty
----------------
39 MB
(1 row)
david=#
3.5 查看指定表中所有索引大小
david=# select pg_indexes_size('test');
pg_indexes_size
-----------------
82477056
(1 row)
david=# select pg_size_pretty(pg_indexes_size('test'));
pg_size_pretty
----------------
79 MB
(1 row)
david=#
idx_test 和idx_join_date_test 两个索引大小加起来差不多等于上面pg_indexes_size() 查询出来的索引大小。
3.6 查看指定schema 里所有的索引大小，按从大到小的顺序排列。
david=# select * from pg_namespace;
nspname | nspowner | nspacl
--------------------+----------+-------------------------------------
pg_toast | 10 |
pg_temp_1 | 10 |
pg_toast_temp_1 | 10 |
pg_catalog | 10 | {postgres=UC/postgres,=U/postgres}
information_schema | 10 | {postgres=UC/postgres,=U/postgres}
public | 10 | {postgres=UC/postgres,=UC/postgres}
(6 rows)
david=# select indexrelname, pg_size_pretty(pg_relation_size(relid)) from pg_stat_user_indexes where schemaname='public' order by pg_relation_size(relid) desc;
indexrelname | pg_size_pretty
-------------------------------+----------------
idx_join_date_test | 91 MB
idx_test | 91 MB
testtable_idx | 1424 kB
city_pkey | 256 kB
city11 | 256 kB
countrylanguage_pkey | 56 kB
sale_pkey | 8192 bytes
track_pkey | 8192 bytes
tbl_partition_201211_joindate | 8192 bytes
tbl_partition_201212_joindate | 8192 bytes
tbl_partition_201301_joindate | 8192 bytes
tbl_partition_201302_joindate | 8192 bytes
tbl_partition_201303_joindate | 8192 bytes
customer_pkey | 8192 bytes
album_pkey | 8192 bytes
item_pkey | 8192 bytes
tbl_partition_201304_joindate | 8192 bytes
tbl_partition_201307_joindate | 8192 bytes
tbl_partition_201305_joindate | 0 bytes
tbl_partition_201306_joindate | 0 bytes
(20 rows)
david=#
3.7 查看指定表大小
david=# select pg_relation_size('test');
pg_relation_size
------------------
95748096
(1 row)
david=# select pg_size_pretty(pg_relation_size('test'));
pg_size_pretty
----------------
91 MB
(1 row)
david=#
使用pg_table_size() 函数查看
david=# select pg_table_size('test');
pg_table_size
---------------
95789056
(1 row)
david=# select pg_size_pretty(pg_table_size('test'));
pg_size_pretty
----------------
91 MB
(1 row)
david=#
3.8 查看指定表的总大小
david=# select pg_total_relation_size('test');
pg_total_relation_size
------------------------
178266112
(1 row)
david=# select pg_size_pretty(pg_total_relation_size('test'));
pg_size_pretty
----------------
170 MB
(1 row)
david=#
3.9 查看指定schema 里所有的表大小，按从大到小的顺序排列。
david=# select relname, pg_size_pretty(pg_relation_size(relid)) from pg_stat_user_tables where schemaname='public' order by pg_relation_size(relid) desc;
relname | pg_size_pretty
-------------------------------+----------------
test | 91 MB
testtable | 1424 kB
city | 256 kB
countrylanguage | 56 kB
country | 40 kB
testcount | 8192 bytes
tbl_partition_201302 | 8192 bytes
tbl_partition_201303 | 8192 bytes
person | 8192 bytes
customer | 8192 bytes
american_state | 8192 bytes
tbl_david | 8192 bytes
emp | 8192 bytes
tbl_partition_201212 | 8192 bytes
tbl_partition_201304 | 8192 bytes
tbl_partition_error_join_date | 8192 bytes
tbl_partition_201211 | 8192 bytes
album | 8192 bytes
tbl_partition_201307 | 8192 bytes
tbl_xulie | 8192 bytes
tbl_partition_201301 | 8192 bytes
sale | 8192 bytes
item | 8192 bytes
track | 8192 bytes
tbl_partition_201306 | 0 bytes
tbl_partition | 0 bytes
tbl_partition_201305 | 0 bytes
person2 | 0 bytes
(28 rows)
david=#
3.10 查看表空间大小
david=# select spcname from pg_tablespace;
spcname
------------
pg_default
pg_global
(2 rows)
david=# select pg_tablespace_size('pg_default');
pg_tablespace_size
--------------------
28381579760
(1 row)
david=# select pg_size_pretty(pg_tablespace_size('pg_default'));
pg_size_pretty
----------------
26 GB
(1 row)
david=#
另一种查看方法：
david=# select pg_tablespace_size('pg_default')/1024/1024 as "SIZE M";
SIZE M
--------
27066
(1 row)
david=# select pg_tablespace_size('pg_default')/1024/1024/1024 as "SIZE G";
SIZE G
--------
26
(1 row)
david=#
