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，*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=#