转载：http://www.cnblogs.com/mchina/archive/2013/04/19/3028573.html
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。
| 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=#
