pg_repack是一个可以在线重建表和索引的扩展。它会在数据库中建立一个和需要清理的目标表一样的临时表，将目标表中的数据COPY到临时表，并在临时表上建立与目标表一样的索引，然后通过重命名的方式用临时表替换目标表。
环境：
1）redhat-release：CentOS Linux release 7.6.1810 (Core)
2）database version：postgresql 14.6
一、部署pg_repack
--解压编译
[postgres@tencent soft]$ unzip pg_repack-master.zip
[postgres@tencent soft]$ cd pg_repack-master/
[postgres@tencent pg_repack-master]$ ll
total 36
drwxrwxr-x 3 postgres postgres 4096 Jun 15 04:53 bin
-rw-rw-r-- 1 postgres postgres 1662 Jun 15 04:53 COPYRIGHT
drwxrwxr-x 2 postgres postgres 4096 Jun 15 04:53 doc
drwxrwxr-x 3 postgres postgres 4096 Jun 15 04:53 lib
-rw-rw-r-- 1 postgres postgres 1616 Jun 15 04:53 Makefile
-rw-rw-r-- 1 postgres postgres 1381 Jun 15 04:53 META.json
drwxrwxr-x 2 postgres postgres 4096 Jun 15 04:53 msvc
-rw-rw-r-- 1 postgres postgres 2191 Jun 15 04:53 README.rst
drwxrwxr-x 4 postgres postgres 4096 Jun 15 04:53 regress
[postgres@tencent pg_repack-master]$ make &&make install
--所在数据库安装pg_repack扩展
[postgres@tencent pg_repack-master]$ psql -d testdb test
psql (14.6)
Type "help" for help.
testdb=# select * from pg_available_extensions where name like 'pg_repack*';
name | default_version | installed_version | comment
------+-----------------+-------------------+---------
(0 rows)
testdb=# create extension pg_repack;
CREATE EXTENSION
testdb=# \dx
List of installed extensions
Name | Version | Schema | Description
-------+-------+----------+---------------------------------------
btree_gist | 1.6 | test | support for indexing common datatypes in GiST
pageinspect | 1.9 | public | inspect the contents of database pages at a low level
pg_freespacemap | 1.2 | test | examine the free space map (FSM)
pg_repack | 1.4.8 | test | Reorganize tables in PostgreSQL databases with minimal locks
pg_visibility | 1.2 | test | examine the visibility map (VM) and page-level visibility info
pgstattuple | 1.5 | test | show tuple-level statistics
plpgsql | 1.0 | pg_catalog | PL/pgSQL procedural language
(7 rows)
--查看pg_repack包含的函数
testdb=# \dxS+ pg_repack
Objects in extension "pg_repack"
Object description
------------------------------------------------------------------
function repack.conflicted_triggers(oid)
function repack.disable_autovacuum(regclass)
function repack.get_alter_col_storage(oid)
function repack.get_assign(oid,text)
function repack.get_columns_for_create_as(oid)
function repack.get_compare_pkey(oid,text)
function repack.get_create_index_type(oid,name)
function repack.get_create_trigger(oid,oid)
function repack.get_drop_columns(oid,text)
function repack.get_enable_trigger(oid)
function repack.get_index_columns(oid,text)
function repack.get_order_by(oid,oid)
function repack.get_storage_param(oid)
function repack.get_table_and_inheritors(regclass)
function repack.oid2text(oid)
function repack.repack_apply(cstring,cstring,cstring,cstring,cstring,integer)
function repack.repack_drop(oid,integer)
function repack.repack_indexdef(oid,oid,name,boolean)
function repack.repack_index_swap(oid)
function repack.repack_swap(oid)
function repack.repack_trigger()
function repack.version()
function repack.version_sql()
schema repack
view repack.primary_keys
view repack.tables
(26 rows)
二、安装pgstattuple模块
（提供多种函数来获得元组层的统计信息）
testdb=# create extension pgstattuple;
CREATE EXTENSION
三、创建测试环境
3.1 创建表（表必须有主键或者唯一约束）
testdb=# create table repack_test(id int primary key ,name varchar(10));
CREATE TABLE
testdb=# \d repack_test
Table "test.repack_test"
Column | Type | Collation | Nullable | Default
--------+-----------------------+-----------+----------+---------
id | integer | | not null |
name | character varying(10) | | |
Indexes:
"repack_test_pkey" PRIMARY KEY, btree (id)
3.2 插入数据
testdb=# insert into repack_test select generate_series(1,50000000),'a';
INSERT 0 50000000
--用pg_stattuple查看表情况
testdb=# select * from pgstattuple('repack_test');
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
------------+-------------+------------+---------------+------------------+----------------+--------------------+------------+--------------
1812389888 | 50000000 | 1500000000 | 82.76 | 0 | 0 | 0 | 6195196 | 0.34
(1 row)
--查看表大小
testdb=# select pg_size_pretty(pg_relation_size('repack_test'));
pg_size_pretty
----------------
1728 MB
(1 row)
3.3 修改表数据
--update 表repack_test
testdb=# update repack_test set name ='b' where id<2500000;
UPDATE 2499999
--用pg_stattuple查看表情况
testdb=# select * from pgstattuple('repack_test');
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
------------+-------------+------------+---------------+------------------+----------------+--------------------+------------+--------------
1903009792 | 50000000 | 1500000000 | 78.82 | 2499999 | 74999970 | 3.94 | 6505400 | 0.34
(1 row)
可以发现产生了2499999条死亡元组。
--查看表大小
testdb=# select pg_size_pretty(pg_relation_size('repack_test'));
pg_size_pretty
----------------
1815 MB
(1 row)
四、执行pg_repack
--执行pg_repack
[postgres@tencent bin]$ ./pg_repack -p 4519 -d testdb -Utest --no-order --table test.repack_test
INFO: repacking table "test.repack_test"
# test.repack_test 表示test模式下repack_test表，默认自动查找postgres数据库下表repack_test，执行过程中会报没有发现表，所以需要指定schema。
另，此处执行没有输入密码，因为配置了.pgpass文件
--用pg_stattuple查看表情况
testdb=# select * from pgstattuple('repack_test');
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
------------+-------------+------------+---------------+------------------+----------------+--------------------+------------+--------------
1812389888 | 50000000 | 1500000000 | 82.76 | 0 | 0 | 0 | 6195196 | 0.34
(1 row)
当前死亡元组数归零。
--查看表大小
testdb=# select pg_size_pretty(pg_relation_size('repack_test'));
pg_size_pretty
----------------
1728 MB
(1 row)
表数据恢复原始大小。
五、pg_repack主要模式
repack数据库：
postgres@node1 contrib]$ pg_repack -p 5432 -d postgres --no-order --jobs 4 --elevel=info
repack模式：
pg_repack -p 5432 -d postgres --schema=public --no-order --jobs 4 --elevel=info
repack表和索引：
pg_repack -p 5432 -d postgres --no-order --table public.repack_test --elevel=info
repack所有索引：
pg_repack -p 5432 -d postgres --no-order --only-indexes --table public.repack_test --elevel=info
repack指定索引：
pg_repack -p 5432 -d postgres --index public.repack_test_pkey --elevel=info
)
