pg9.5升级 到 pg11 的步骤：
## 这里pg9.5 和 pg11 都使用rpm包安装。
pg9.5 已经在运行，参数如下：
[root@node77 data]# egrep "^\w+" postgresql.conf
listen_addresses = '*' # what IP address(es) to listen on;
port = 5432 # (change requires restart)
max_connections = 100 # (change requires restart)
shared_buffers = 128MB # min 128kB
dynamic_shared_memory_type = posix # the default is the first option
wal_level = hot_standby # minimal, archive, hot_standby, or logical
fsync = on # turns forced synchronization on or off
wal_sync_method = fsync # the default is the first option
full_page_writes = on # recover from partial page writes
max_wal_size = 1GB
min_wal_size = 80MB
archive_mode = on # enables archiving; off, on, or always
archive_command = 'cd ./' # command to use to archive a logfile segment
max_wal_senders = 10 # max number of walsender processes
wal_keep_segments = 100 # in logfile segments, 16MB each; 0 disables
wal_sender_timeout = 60s # in milliseconds; 0 disables
hot_standby = on # "on" allows queries during recovery
log_destination = 'stderr' # Valid values are combinations of
logging_collector = on # Enable capturing of stderr and csvlog
log_directory = 'pg_log' # directory where log files are written,
log_filename = 'postgresql-%a.log' # log file name pattern,
log_truncate_on_rotation = on # If on, an existing log file with the
log_rotation_age = 1d # Automatic rotation of logfiles will
log_rotation_size = 0 # Automatic rotation of logfiles will
log_checkpoints = on
log_connections = on
log_duration = on
log_line_prefix = '< %m >' # special values:
log_statement = 'ddl' # none, ddl, mod, all
log_timezone = 'PRC'
autovacuum = on # Enable autovacuum subprocess? 'on'
datestyle = 'iso, mdy'
timezone = 'PRC'
lc_messages = 'en_US.UTF-8' # locale for system error message
lc_monetary = 'en_US.UTF-8' # locale for monetary formatting
lc_numeric = 'en_US.UTF-8' # locale for number formatting
lc_time = 'en_US.UTF-8' # locale for time formatting
default_text_search_config = 'pg_catalog.english'
pg9.5 的编译参数如下：
[root@node77 data]# /usr/pgsql-9.5/bin/pg_config
BINDIR = /usr/pgsql-9.5/bin
DOCDIR = /usr/pgsql-9.5/doc
HTMLDIR = /usr/pgsql-9.5/doc/html
INCLUDEDIR = /usr/pgsql-9.5/include
PKGINCLUDEDIR = /usr/pgsql-9.5/include
INCLUDEDIR-SERVER = /usr/pgsql-9.5/include/server
LIBDIR = /usr/pgsql-9.5/lib
PKGLIBDIR = /usr/pgsql-9.5/lib
LOCALEDIR = /usr/pgsql-9.5/share/locale
MANDIR = /usr/pgsql-9.5/share/man
SHAREDIR = /usr/pgsql-9.5/share
SYSCONFDIR = /etc/sysconfig/pgsql
PGXS = /usr/pgsql-9.5/lib/pgxs/src/makefiles/pgxs.mk
CONFIGURE = '--enable-rpath' '--prefix=/usr/pgsql-9.5' '--includedir=/usr/pgsql-9.5/include' '--mandir=/usr/pgsql-9.5/share/man' '--datadir=/usr/pgsql-9.5/share' '--with-perl' '--with-python' '--with-tcl' '--with-tclconfig=/usr/lib64' '--with-openssl' '--with-pam' '--with-gssapi' '--with-includes=/usr/include' '--with-libraries=/usr/lib64' '--enable-nls' '--enable-dtrace' '--with-uuid=e2fs' '--with-libxml' '--with-libxslt' '--with-ldap' '--with-selinux' '--with-system-tzdata=/usr/share/zoneinfo' '--sysconfdir=/etc/sysconfig/pgsql' '--docdir=/usr/pgsql-9.5/doc' '--htmldir=/usr/pgsql-9.5/doc/html' 'CFLAGS=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' 'LDFLAGS=-Wl,--as-needed'
CC = gcc
CPPFLAGS = -D_GNU_SOURCE -I/usr/include/libxml2 -I/usr/include
CFLAGS = -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic
CFLAGS_SL = -fPIC
LDFLAGS = -Wl,--as-needed -L/usr/lib64 -Wl,--as-needed -Wl,-rpath,'/usr/pgsql-9.5/lib',--enable-new-dtags
LDFLAGS_EX =
LDFLAGS_SL =
LIBS = -lpgcommon -lpgport -lselinux -lxslt -lxml2 -lpam -lssl -lcrypto -lgssapi_krb5 -lz -lreadline -lrt -lcrypt -ldl -lm
VERSION = PostgreSQL 9.5.15
### 然后 随便在pg9.5上造点测试数据，过程忽略 ###
在同一台机器上，安装下 pg11的 rpm包：
[root@node77 pg11_el7]# l
total 9.4M
-rw-r--r-- 1 root root 616K 2019-03-08 17:16 postgresql11-contrib-11.2-2PGDG.rhel7.x86_64.rpm
-rw-r--r-- 1 root root 1.7M 2019-03-08 17:16 postgresql11-11.2-2PGDG.rhel7.x86_64.rpm
-rw-r--r-- 1 root root 360K 2019-03-08 17:16 postgresql11-libs-11.2-2PGDG.rhel7.x86_64.rpm
-rw-r--r-- 1 root root 2.1M 2019-03-08 17:16 postgresql11-devel-11.2-2PGDG.rhel7.x86_64.rpm
-rw-r--r-- 1 root root 4.8M 2019-03-08 17:16 postgresql11-server-11.2-2PGDG.rhel7.x86_64.rpm
## 安装并初始化下 pg11 的文件目录
[root@node77 pg11_el7]# yum localinstall postgresql11-*
### 修改配置文件，确保端口和老的实例不冲突
su - postgresql
-bash-4.2$ cd /var/lib/pgsql/11/data/
-bash-4.2$ egrep "^\w+" postgresql.conf 参数如下：
listen_addresses = '*' # what IP address(es) to listen on;
port = 5433 # (change requires restart)
max_connections = 100 # (change requires restart)
shared_buffers = 128MB # min 128kB
dynamic_shared_memory_type = posix # the default is the first option
wal_level = replica # minimal, replica, or logical
fsync = on # flush data to disk for crash safety
wal_sync_method = fsync # the default is the first option
full_page_writes = on # recover from partial page writes
max_wal_size = 1GB
min_wal_size = 80MB
archive_mode = on # enables archiving; off, on, or always
archive_command = 'cd ./' # command to use to archive a logfile segment
max_wal_senders = 10 # max number of walsender processes
wal_keep_segments = 100 # in logfile segments; 0 disables
wal_sender_timeout = 60s # in milliseconds; 0 disables
hot_standby = on # "off" disallows queries during recovery
log_destination = 'stderr' # Valid values are combinations of
logging_collector = on # Enable capturing of stderr and csvlog
log_directory = 'pg_log' # directory where log files are written,
log_filename = 'postgresql-%a.log' # log file name pattern,
log_truncate_on_rotation = on # If on, an existing log file with the
log_rotation_age = 1d # Automatic rotation of logfiles will
log_rotation_size = 0 # Automatic rotation of logfiles will
log_checkpoints = on
log_connections = on
log_duration = on
log_line_prefix = '%m [%p] ' # special values:
log_timezone = 'PRC'
autovacuum = on # Enable autovacuum subprocess? 'on'
datestyle = 'iso, mdy'
timezone = 'PRC'
lc_messages = 'en_US.UTF-8' # locale for system error message
lc_monetary = 'en_US.UTF-8' # locale for monetary formatting
lc_numeric = 'en_US.UTF-8' # locale for number formatting
lc_time = 'en_US.UTF-8' # locale for time formatting
default_text_search_config = 'pg_catalog.english'
# 先初始化一个pg11的数据库实例出来
su - postgresql
/usr/pgsql-11/bin/pg_ctl initdb -D /var/lib/pgsql/11/data/
下面准备开始做升级任务
# 1 关闭 pg9.5
# 2 关闭 pg11 （默认我们上面只是初始化了下pg11，并没有启动）
# 3 检测pg11下 是否可升级
su - postgres
/usr/pgsql-11/bin/pg_upgrade -b /usr/pgsql-9.5/bin -B /usr/pgsql-11/bin/ -d /var/lib/pgsql/9.5/data/ -D /var/lib/pgsql/11/data/ -p 5432 -P 5433 -U postgres -j 8 --link --check
结果类似下面这样：
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 roles starting with "pg_" ok
Checking for presence of required libraries ok
Checking database user is the install user ok
Checking for prepared transactions ok
*Clusters are compatible*
上面都是OK就是没问题的，我们可以继续第四步。
# 4 正式执行 upgrade操作
# pg_upgrade有两种升级方式，一个是缺省的通过拷贝数据文件到新的data目录下，一个是创建硬链接。拷贝的方式升级较慢，但是原库还可用；硬链接的方式升级较快，但是原库不可用。
# 缺省拷贝方式升级的命令，(硬链接方式升级的命令只需要添加 -k 或者 --link)
su - postgres
/usr/pgsql-11/bin/pg_upgrade -b /usr/pgsql-9.5/bin -B /usr/pgsql-11/bin/ -d /var/lib/pgsql/9.5/data/ -D /var/lib/pgsql/11/data/ -p 5432 -P 5433 -U postgres -j 8 --link --retain --verbose ## 这里使用硬链接方式升级
结果类似下面这样：
"/usr/pgsql-11/bin/pg_ctl" -w -D "/var/lib/pgsql/11/data/" -o "" -m smart stop >> "pg_upgrade_server.log" 2>&1
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
# 5 修改配置文件，并启动pg11 数据库 【注意暂时不要让业务连接进来】
su - postgres
vim /var/lib/pgsql/11/data/postgresql.conf 修改 port = 5432 还有其他一些文件的路径配置即可
/usr/pgsql-11/bin/pg_ctl start -D /var/lib/pgsql/11/data/
/usr/pgsql-11/bin/psql
# 6 重建下统计信息
实际上执行的是这个命令：/usr/pgsql-11/bin/vacuumdb -U postgres --all --analyze-only
注意： 全库的vacuumdb 操作，比较重量级，因此最好自己手工对重要的大表执行下。
有时候，pgsql大版本升级，psql连接问题会报这个错误：undefined symbol: PQsetErrorContextVisibility
解决方法：
su - postgres
vim .bash_profile 加一行
export LD_LIBRARY_PATH=/usr/pgsql-10/lib
没有ZFS的情况下的，pg的升级建议：
1、新加一台pg流复制从库X
2、在pg流复制的从库X，使用pg_upgrade进行升级（硬链接比较快）
3、低峰期，切换主从复制关系
关于 pg_upgrade 的文章， 可以看德哥的这篇：
https://github.com/digoal/blog/blob/master/201412/20141219_01.md?spm=a2c4e.11153940.blogcont640709.22.1ffc508cWN9t9E&file=20141219_01.md