postgresql10.3 检查点调整

文章中的函数与使用的pg10.3有差别，如下 pg_xlog_location_diff            pg_wal_lsn_diff pg_current_xlog_location         pg_current_wal_lsn pg_current_xlog_insert_location  pg_current_wal_insert_lsn 链接地址：https://blog.2ndquadrant.com/basics-of-tuning-checkpoints/