PostgreSQL 12 开始 recovery.conf配置整合到postgresql.conf中

官方文档说明：

Integrate recovery.conf into postgresql.conf
 
recovery.conf settings are now set in postgresql.conf (or other GUC
sources).  Currently, all the affected settings are PGC_POSTMASTER;
this could be refined in the future case by case.
 
Recovery is now initiated by a file recovery.signal.  Standby mode is
initiated by a file standby.signal.  The standby_mode setting is
gone.  If a recovery.conf file is found, an error is issued.
 
The trigger_file setting has been renamed to promote_trigger_file as
part of the move.

主要包括以下几点：

• recovery.conf 配置文件不再支持，此文件中的参数合并到 postgresql.conf中，如果数据文件目录中存在recovery.conf 文件，数据库将无法启动。
• 新增 recovery.signal 标识文件，表示数据库处于 recovery 模式
• 新增加 standby.signal 标识文件，表示数据库处于 standby 模式
• trigger_file 参数更名为 promote_trigger_file
• standby_mode 参数不再支持