Hello, I find this proposed patch a bit strange and I feel it needs more explanation.
When this thread started, Bharath justified his patches saying that a slot that's inactive for a very long time could be problematic because of XID wraparound. Fine, that sounds a reasonable feature. If you wanted to invalidate slots whose xmins were too old, I would support that. He submitted that as his 0004 patch then. However, he also chose to submit 0003 with invalidation based on a timeout. This is far less convincing a feature to me. The justification for the time out seems to be that ... it's difficult to have a one-size-fits-all value because size of disks vary. (???) Or something like that. Really? I mean -- yes, this will prevent problems in toy databases when run in developer's laptops. It will not prevent any problems in production databases. Do we really want a setting that is only useful for toy situations rather than production? Anyway, the thread is way too long, but after some initial pieces were committed, Nisha took over and submitting patches derived from Bharath's 0003, and at some point the initial 0004 was dropped. But 0004 was the more useful one, I thought, so what's going on? I'm baffled. -- Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/ Officer Krupke, what are we to do? Gee, officer Krupke, Krup you! (West Side Story, "Gee, Officer Krupke")
