On 2020-Aug-17, Ashutosh Sharma wrote: > > + if (heap_force_opt == HEAP_FORCE_KILL) > > + ItemIdSetDead(itemid); > > > > I think that if the page is an all-visible page, we should clear an > > all-visible bit on the visibility map corresponding to the page and > > PD_ALL_VISIBLE on the page header. Otherwise, index only scan would > > return the wrong results. > > I think we should let VACUUM do that. Please note that this module is > intended to be used only on a damaged relation and should only be > operated on damaged tuples of such relations. And the execution of any > of the functions provided by this module on a damaged relation must be > followed by VACUUM with DISABLE_PAGE_SKIPPING option on that relation. > This is necessary to bring back a damaged relation to the sane state > once a surgery is performed on it. I will try to add this note in the > documentation for this module.
It makes sense to recommend VACUUM after fixing the page, but I agree with Sawada-san that it would be sensible to reset the VM bit while doing surgery, since that's the state that the page would be in. We should certainly *strongly recommend* to do VACUUM DISABLE_PAGE_SKIPPING, but if users fail to do so, then leaving the VM bit set just means that we know *for certain* that there will be further corruption as soon as the XID counter advances sufficiently. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
