Hello, I'd like to propose a new feature, Deadline-Based Vacuum Delay, the syntax is something like "VACUUM IN 6 HOURS".
Vacuum is a non-trivial task to be performed. The database needs to be vacuumed before the system performance suffers from the garbage; it also needs to ensure the system won't be hammered during the vacuum operation. The cost-based delay vacuum can reduce the impact of the disk I/O storm, but sometimes it can last for several hours and it is hard to know when it will end. So there are many complains about the unpredictable execution time of vacuum. On the other hand, several users want to run vacuum in their maintenance window. Also, autovacuum kicks vacuum when a certain amount of garbage has been generated. It restricts the interval of each vacuum for a relation. So I am thinking another way to perform vacuum. For example vacuum can be refined in a maintenance time frame like "VACUUM IN 6 HOURS", and then vacuum operation will be performed within the window. The delay time is adjusted internally to spread the disk I/O over the time frame. This may make vacuum more predictable, also ensures vacuum doesn't have side effect on the producing system outside the maintenance window. Any ideas or comments? Best Regards, -- Galy Lee NTT Open Source Software Center ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match