1 背景
一般來說，數據庫的升級很少遇到，除非確實出現了新的業務需求或者系統bug無法解決的情況下才選擇升級。本文基本測試了一下pg9.6升級到10.5的過程，沒有遇到太大的問題。
2 升級
之前博客中有介紹，其實postgresql和mysql的安裝邏輯結構很相似，數據和程序時分開的，啟動時候指定啟動的數據目錄，當然數據目錄是可以放在配置文件中。今天測試了一下使用pg10.5的版本去打開pg9.6版本初始化的數據庫出現了錯誤，錯誤中顯示的是數據庫文件不兼容。
[postgres@pgmaster ~]$ pg_ctl -D /data/pgdata/ start
waiting for server to start....2019-10-08 16:56:20.203 CST [35441] FATAL: database files are incompatible with server
2019-10-08 16:56:20.203 CST [35441] DETAIL: The data directory was initialized by PostgreSQL version 9.6, which is not compatible with this version 10.5.
stopped waiting
pg_ctl: could not start server
Examine the log output.
2.1 升級工具
在程序的bin目錄下，提供了很多的數據庫工具，有一個pg_upgrade的工具就是專門用於數據庫升級的。關於該工具可以使用幫助命令來查看具體的用法：
[postgres@pgmaster pgdata]$ pg_upgrade --help
pg_upgrade upgrades a PostgreSQL cluster to a different major version.
Usage:
pg_upgrade [OPTION]...
Options:
-b, --old-bindir=BINDIR old cluster executable directory
-B, --new-bindir=BINDIR new cluster executable directory
-c, --check check clusters only, don't change any data
-d, --old-datadir=DATADIR old cluster data directory
-D, --new-datadir=DATADIR new cluster data directory
-j, --jobs number of simultaneous processes or threads to use
-k, --link link instead of copying files to new cluster
-o, --old-options=OPTIONS old cluster options to pass to the server
-O, --new-options=OPTIONS new cluster options to pass to the server
-p, --old-port=PORT old cluster port number (default 50432)
-P, --new-port=PORT new cluster port number (default 50432)
-r, --retain retain SQL and log files after success
-U, --username=NAME cluster superuser (default "postgres")
-v, --verbose enable verbose internal logging
-V, --version display version information, then exit
-?, --help show this help, then exit
Before running pg_upgrade you must:
create a new database cluster (using the new version of initdb)
shutdown the postmaster servicing the old cluster
shutdown the postmaster servicing the new cluster
When you run pg_upgrade, you must provide the following information:
the data directory for the old cluster (-d DATADIR)
the data directory for the new cluster (-D DATADIR)
the "bin" directory for the old version (-b BINDIR)
the "bin" directory for the new version (-B BINDIR)
For example:
pg_upgrade -d oldCluster/data -D newCluster/data -b oldCluster/bin -B newCluster/bin
or
$ export PGDATAOLD=oldCluster/data
$ export PGDATANEW=newCluster/data
$ export PGBINOLD=oldCluster/bin
$ export PGBINNEW=newCluster/bin
$ pg_upgrade
Report bugs to <pgsql-bugs@postgresql.org>.
幫助文件中，提到了使用pg_upgrade工具前，必須創建一個新的數據庫，並且是已經初始化的，同時關閉原來的數據庫和新的數據庫。使用pg_upgrade時候，必須要加上前后版本的data目錄和bin目錄。
2.2 升級過程
首先確認的是，原來的數據庫版本是pg9.6，數據目錄在/data/pgdata。然后，安裝完pg10.5后，不要初始化目錄。
- 將原來的9.6版本數據目錄重命名為pgdata.old
mv /data/pgdata /data/pgdata.old
- 在/data/下創建一個pgdata目錄，作為新版本的數據庫數據目錄，需要注意的是，這個目錄權限是700，owner是postgres
cd /data/
mkdir pgdata
chmod 700 pgdata
chown -R postgres.postgres pgdata
- 使用pg10.5的initdb初始化/data/pgdata目錄
initdb -D /data/pgdata
- 進行升級check，注意后面加上-c，這一步只是檢查不會實際執行升級。所有項都是ok即認為是可以升級。
[postgres@pgmaster ~]$ pg_upgrade -b /usr/local/pgsql-9.6/bin -B /usr/local/pgsql/bin/ -d /data/pgdata.old/ -D /data/pgdata -p 5432 -P 5432 -c
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 reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for invalid "unknown" user columns ok
Checking for hash indexes ok
Checking for presence of required libraries ok
Checking database user is the install user ok
Checking for prepared transactions ok
*Clusters are compatible*
- 執行升級。即在上一步去掉-c，需要注意的是這一步根據數據庫的大小執行時間長短不一，執行完畢后會產生兩個腳本analyze_new_cluster.sh和delete_old_cluster.sh，根據實際需要來進行執行，一般都會執行第一個腳本，第二個不建議執行，以防需要回滾升級，保留原來的數據目錄比較保險。
[postgres@pgmaster ~]$ pg_upgrade -b /usr/local/pgsql-9.6/bin -B /usr/local/pgsql/bin/ -d /data/pgdata.old/ -D /data/pgdata -p 5432 -P 5432
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 reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for invalid "unknown" user columns 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
If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.
Performing Upgrade
------------------
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_clog to new server 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 analyze new cluster ok
Creating script to delete old cluster ok
Checking for hash indexes ok
Upgrade Complete
----------------
Optimizer statistics are not transferred by pg_upgrade so,
once you start the new server, consider running:
./analyze_new_cluster.sh
Running this script will delete the old cluster's data files:
./delete_old_cluster.sh
- 執行腳本前，需要先啟動數據庫pg_ctl -D /data/pgdata start
[postgres@pgmaster ~]$ pg_ctl -D /data/pgdata start
waiting for server to start....2019-10-08 17:18:51.402 CST [35827] LOG: listening on IPv6 address "::1", port 5432
2019-10-08 17:18:51.402 CST [35827] LOG: listening on IPv4 address "127.0.0.1", port 5432
2019-10-08 17:18:51.408 CST [35827] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2019-10-08 17:18:51.437 CST [35828] LOG: database system was shut down at 2019-10-08 17:16:11 CST
2019-10-08 17:18:51.442 CST [35827] LOG: database system is ready to accept connections
done
server started
- 執行腳本./analyze_new_cluster.sh ，從運行日志來看，主要是創建統計信息
[postgres@pgmaster ~]$ ./analyze_new_cluster.sh
This script will generate minimal optimizer statistics rapidly
so your system is usable, and then gather statistics twice more
with increasing accuracy. When it is done, your system will
have the default level of optimizer statistics.
If you have used ALTER TABLE to modify the statistics target for
any tables, you might want to remove them and restore them after
running this script because they will delay fast statistics generation.
If you would like default statistics as quickly as possible, cancel
this script and run:
"/usr/local/pgsql/bin/vacuumdb" --all --analyze-only
vacuumdb: processing database "postgres": Generating minimal optimizer statistics (1 target)
vacuumdb: processing database "template1": Generating minimal optimizer statistics (1 target)
vacuumdb: processing database "test": Generating minimal optimizer statistics (1 target)
vacuumdb: processing database "postgres": Generating medium optimizer statistics (10 targets)
vacuumdb: processing database "template1": Generating medium optimizer statistics (10 targets)
vacuumdb: processing database "test": Generating medium optimizer statistics (10 targets)
vacuumdb: processing database "postgres": Generating default (full) optimizer statistics
vacuumdb: processing database "template1": Generating default (full) optimizer statistics
vacuumdb: processing database "test": Generating default (full) optimizer statistics
Done
- 至此，查看version，發現已經由原來的9.6升級為10.5，升級結束。
postgres=# select version();
version
---------------------------------------------------------------------------------------------------------
PostgreSQL 10.5 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit
(1 row)
3 總結
本文只是簡單測試了了升級的步驟，整個過程中可能會出現其他的問題，歡迎大家留言一起探討。