数据库进行升级，是一个再正常不过的功能，比如功能的需要，遇到BUG，安全漏洞等等，具体升级包含子版本升级，主版本升级。如果用过ORACLE的朋友，一定知道，在ORACLE中，如果要实现大版本的升级，比如从11g,升级到19c,一般使用的dbua来完成，并且标准的升级，一定会有数据库停机时间，小版本的升级，如19.3,升级到19.24 ，使用OPATCH 工具来完成，一样需要停数据库。
那对于PG，一样也存在升级，如果是小版本升级，比如12.0 升级到12.19 ,直接使用二进制文件替换即可，如果是大版本升级，一般使用 pg_upgrade来完成，当然，如果时间允许，也可以使用pg_dumpall也行。只是时间要长一些。
关于PG_UPGRADE的使用，可以参见官方文档：PostgreSQL: Documentation: 16: pg_upgrade
部分截图如下：
PG_UPGRADE 的用法：
pg_upgrade -b oldbindir [-B newbindir ] -d oldconfigdir -D newconfigdir [option...]
目前pg_upgrade 支持从 9.2.x 到目前最新的版本，甚至BETA版本。
下面我们以一个升级案例来说明：
目录
1.升级环境
源版本：pg 12.0
PGHOME=/u01/app/postgres/product/12.0/dbhome_1
PGDATA=/u01/app/postgres/product/pgdata_12
PORT=5432
目标版本：pg 16.3
PGHOME=/u01/app/postgres/product/16.3/dbhome_1
PGDATA=/u01/app/postgres/product/pgdata
PORT=5432
操作系统：OpenEuler 24.03
sztechdb=# select * from version();
version
PostgreSQL 12.0 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 12.3.1 (openEuler 12.3.1-30.oe2403), 64-bit
(1 row)
2.源码安装新版本16.3
这个步骤，可以参见前面的文档：https://blog.csdn.net/cqsztech/article/details/140748640
如果源端有额外的插件，需要安装
这里安装，只需要到 initdb即可,不需要打开
postgres@openeuler2403 bin]$ ./initdb --pgdata=/u01/app/postgres/pgdata -U postgres
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.
The database cluster will be initialized with locale "zh_CN.UTF-8".
The default database encoding has accordingly been set to "UTF8".
initdb: could not find suitable text search configuration for locale "zh_CN.UTF-8"
The default text search configuration will be set to "simple".
Data page checksums are disabled.
fixing permissions on existing directory /u01/app/postgres/pgdata ... ok
creating subdirectories ... ok
selecting dynamic shared memory implementation ... posix
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting default time zone ... Asia/Shanghai
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
syncing data to disk ... ok
initdb: warning: enabling "trust" authentication for local connections
initdb: hint: You can change this by editing pg_hba.conf or using the option -A, or --auth-local and --auth-host, the next time you run initdb.
Success. You can now start the database server using:
pg_ctl -D /u01/app/postgres/pgdata -l logfile start
3.关闭源和目标数据库
把源和目标数据库都关闭。
[postgres@openeuler2403 pgdata_12]$ pg_ctl stop
waiting for server to shut down.... done
server stopped
4.执行升级检查
是否能升级，正式升级之前，可以先检查一下，有点试升级的味道。
注意，执行PG_UPGRADE命令，需要在高版本的环境下运行
先看看pg_upgrade 的用法：
[postgres@openeuler2403 bin]$ pg_upgrade -c --old-datadir=/u01/app/postgres/pgdata_12 \
> --new-datadir=/u01/app/postgres/pgdata \
> --old-bindir=/u01/app/postgres/product/12.0/dbhome_1/bin \
> --new-bindir=/u01/app/postgres/product/16.3/dbhome_1/bin
查看丢失的库是什么
[postgres@openeuler2403 pgdata_12]$ cat /u01/app/postgres/pgdata/pg_upgrade_output.d/20240801T164259.299/loadable_libraries.txt
could not load library "libdir/pgcrypto": ERROR: could not access file "libdir/pgcrypto": ûĿ¼
In database: postgres
--暂时源端去掉这个插件
postgres=# drop extension pgcrypto;
DROP EXTENSION
再次检查，OK。
5.正式升级
[postgres@openeuler2403 bin]$ pg_upgrade --old-datadir=/u01/app/postgres/pgdata_12 \
> --new-datadir=/u01/app/postgres/pgdata \
> --old-bindir=/u01/app/postgres/product/12.0/dbhome_1/bin \
> --new-bindir=/u01/app/postgres/product/16.3/dbhome_1/bin
Performing Consistency Checks
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for system-defined composite types in user tables ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for incompatible "aclitem" data type in user tables ok
Checking for user-defined encoding conversions ok
Checking for user-defined postfix operators ok
Checking for incompatible polymorphic functions ok
Creating dump of global objects ok
Creating dump of database schemas
ok
Checking for presence of required libraries ok
Checking database user is the install user ok
Checking for prepared transactions ok
Checking for new cluster tablespace directories ok
If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.
Performing Upgrade
Setting locale and encoding for new cluster ok
Analyzing all rows in the new cluster ok
Freezing all rows in the new cluster ok
Deleting files from new pg_xact ok
Copying old pg_xact to new server ok
Setting oldest XID for new cluster ok
Setting next transaction ID and epoch for new cluster ok
Deleting files from new pg_multixact/offsets ok
Copying old pg_multixact/offsets to new server ok
Deleting files from new pg_multixact/members ok
Copying old pg_multixact/members to new server ok
Setting next multixact ID and offset for new cluster ok
Resetting WAL archives ok
Setting frozenxid and minmxid counters in new cluster ok
Restoring global objects in the new cluster ok
Restoring database schemas in the new cluster
ok
Copying user relation files
ok
Setting next OID for new cluster ok
Sync data directory to disk ok
Creating script to delete old cluster ok
Checking for extension updates notice
Your installation contains extensions that should be updated
with the ALTER EXTENSION command. The file
update_extensions.sql
when executed by psql by the database superuser will update
these extensions.
Upgrade Complete
Optimizer statistics are not transferred by pg_upgrade.
Once you start the new server, consider running:
/u01/app/postgres/product/16.3/dbhome_1/bin/vacuumdb --all --analyze-in-stages
Running this script will delete the old cluster's data files:
./delete_old_cluster.sh
[postgres@openeuler2403 bin]$
6.修改环境变量
[postgres@openeuler2403 bin]$ cat ~/.bash_profile
Source /root/.bashrc if user has one
[ -f ~/.bashrc ] && . ~/.bashrc
export PGPORT=5432
export PGDATA=/u01/app/postgres/pgdata
export PGHOME=/u01/app/postgres/product/16.3/dbhome_1
export LD_LIBRARY_PATH=PGHOME/lib:LD_LIBRARY_PATH
export PATH=PGHOME/bin:PATH:.
export PGHOST=$PGDATA
export PGUSER=postgres
export PGDATABASE=postgres
export PGCLIENTENCODING=GBK
7.修改初始参数
cat >> $PGDATA/postgresql.conf << "EOF"
listen_addresses = '*'
port=5432
unix_socket_directories='/u01/app/postgres/pgdata'
logging_collector = on
log_directory = 'pg_log'
log_filename = 'postgresql-%a.log'
log_truncate_on_rotation = on
max_connections = 500
shared_buffers = 2GB
EOF
cat >> $PGDATA/pg_hba.conf << "EOF"
TYPE DATABASE USER ADDRESS METHOD
host all all 0.0.0.0/0 md5
EOF
8.启动PG并调整PG_UPGRADE要求的脚本
--插件更新
[postgres@openeuler2403 pgdata]$ psql -f /u01/app/postgres/product/16.3/dbhome_1/bin/update_extensions.sql
You are now connected to database "postgres" as user "postgres".
ALTER EXTENSION
ALTER EXTENSION
ALTER EXTENSION
--收集统计信息
[postgres@openeuler2403 pgdata]$ /u01/app/postgres/product/16.3/dbhome_1/bin/vacuumdb --all --analyze-in-stages
vacuumdb: processing database "postgres": Generating minimal optimizer statistics (1 target)
vacuumdb: processing database "sztechdb": Generating minimal optimizer statistics (1 target)
vacuumdb: processing database "template1": Generating minimal optimizer statistics (1 target)
vacuumdb: processing database "postgres": Generating medium optimizer statistics (10 targets)
vacuumdb: processing database "sztechdb": Generating medium optimizer statistics (10 targets)
vacuumdb: processing database "template1": Generating medium optimizer statistics (10 targets)
vacuumdb: processing database "postgres": Generating default (full) optimizer statistics
vacuumdb: processing database "sztechdb": Generating default (full) optimizer statistics
vacuumdb: processing database "template1": Generating default (full) optimizer statistics
--删除老版本的文件
[postgres@openeuler2403 pgdata]$ cat /u01/app/postgres/product/16.3/dbhome_1/bin/delete_old_cluster.sh
#!/bin/sh
rm -rf '/u01/app/postgres/pgdata_12'
rm -rf '/data/pgdata/PG_12_201909212'
[postgres@openeuler2403 pgdata]$ /u01/app/postgres/product/16.3/dbhome_1/bin/delete_old_cluster.sh
[postgres@openeuler2403 pgdata]$ ls -ltr /u01/app/postgres/
总计 8
drwxrwxr-x. 4 postgres postgres 30 7月31日 17:53 product
drwxr-xr-x. 2 postgres postgres 4096 7月31日 19:17 archive_log
drwx------. 21 postgres postgres 4096 8月 1日 17:36 pgdata
[postgres@openeuler2403 pgdata]$ ls -ltr /data/pgdata/
总计 8
drwx------ 3 postgres postgres 4096 8月 1日 09:23 PG_16_202307071_bak
drwx------ 3 postgres postgres 4096 8月 1日 17:27 PG_16_202307071
9.结果验证
到此，PG_UPGRADE 升级就完成了。
但感觉PG_UPGRADE还是有一些遗憾，
1.整个升级，都是命令行完成，没有图形界面，不太直观
2.升级过程中，数据文件路径要变化，不能就数据文件原地升级，也许是强迫症吧。
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