pgstattuple

os: centos 7.4
db: postgresql 11.5

pgstattuple 包含在 postgresql11-contrib，只需要安装这个包即可。
pgstattuple 查看表的相关信息非常方便。

版本

# cat /etc/centos-release
CentOS Linux release 7.4.1708 (Core) 
# su - postgres
Last login: Mon Oct 21 11:01:23 CST 2019 on pts/0

$ psql -c "select version();"
                                                 version                                                 
---------------------------------------------------------------------------------------------------------
 PostgreSQL 11.5 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36), 64-bit
(1 row)

pgstattuple

$ cd /usr/pgsql-11/
$ ls -l ./lib/pgstat*
-rwxr-xr-x. 1 root root 28224 Aug  8 06:20 ./lib/pgstattuple.so

$ ls -l ./share/extension/pgstat*
-rw-r--r--. 1 root root  400 Aug  8 06:20 ./share/extension/pgstattuple--1.0--1.1.sql
-rw-r--r--. 1 root root 1435 Aug  8 06:20 ./share/extension/pgstattuple--1.1--1.2.sql
-rw-r--r--. 1 root root 1126 Aug  8 06:20 ./share/extension/pgstattuple--1.2--1.3.sql
-rw-r--r--. 1 root root  623 Aug  8 06:20 ./share/extension/pgstattuple--1.3--1.4.sql
-rw-r--r--. 1 root root 5506 Aug  8 06:20 ./share/extension/pgstattuple--1.4--1.5.sql
-rw-r--r--. 1 root root 3764 Aug  8 06:20 ./share/extension/pgstattuple--1.4.sql
-rw-r--r--. 1 root root  147 Aug  8 06:20 ./share/extension/pgstattuple.control
-rw-r--r--. 1 root root  457 Aug  8 06:20 ./share/extension/pgstattuple--unpackaged--1.0.sql

$ psql
psql (11.5)
Type "help" for help.

postgres=#
postgres=# select * from pg_available_extensions where name like 'pgstat%';
    name     | default_version | installed_version |           comment           
-------------+-----------------+-------------------+-----------------------------
 pgstattuple | 1.5             |                   | show tuple-level statistics
(1 row)

postgres=# 
postgres=# create extension pgstattuple;
CREATE EXTENSION
postgres=# 
postgres=# \dx
                   List of installed extensions
    Name     | Version |   Schema   |         Description          
-------------+---------+------------+------------------------------
 pgstattuple | 1.5     | public     | show tuple-level statistics
 plpgsql     | 1.0     | pg_catalog | PL/pgSQL procedural language
(2 rows)

postgres=# \dxS+ pgstattuple
  Objects in extension "pgstattuple"
          Object description           
---------------------------------------
 function pg_relpages(regclass)
 function pg_relpages(text)
 function pgstatginindex(regclass)
 function pgstathashindex(regclass)
 function pgstatindex(regclass)
 function pgstatindex(text)
 function pgstattuple_approx(regclass)
 function pgstattuple(regclass)
 function pgstattuple(text)
(9 rows)

postgres=# SELECT * FROM pgstattuple('public.t_log');
 table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent 
-----------+-------------+-----------+---------------+------------------+----------------+--------------------+------------+--------------
      8192 |           2 |        96 |          1.17 |                0 |              0 |                  0 |       8060 |        98.39
(1 row)

列名解释

Column           Type        Description
table_len          bigint     Physical relation length in bytes
tuple_count        bigint     Number of live tuples
tuple_len          bigint     Total length of live tuples in bytes
tuple_percent      float8     Percentage of live tuples
dead_tuple_count   bigint     Number of dead tuples
dead_tuple_len     bigint     Total length of dead tuples in bytes
dead_tuple_percent float8     Percentage of dead tuples
free_space         bigint     Total free space in bytes
free_percent       float8     Percentage of free space

参考:
https://www.postgresql.org/docs/11/pgstattuple.html