On 2017-11-09 16:02:17 -0800, Peter Geoghegan wrote: > > What I'm currently wondering about is how much we need to harden > > postgres against such existing corruption. If e.g. the hot chains are > > broken somebody might have reindexed thinking the problem is fixed - but > > if they then later vacuum everything goes to shit again, with dead rows > > reappearing. > > I don't follow you here. Why would REINDEXing make the rows that > should be dead disappear again, even for a short period of time?
It's not the REINDEX that makes them reappear. It's the second vacuum. The reindex part was about $user trying to fix the problem... As you need two vacuums with appropriate cutoffs to hit the "rows revive" problem, that'll often in practice not happen immediately. > Actually, on second thought, I take that back -- I don't think that > REINDEXing will even finish once a HOT chain is broken by the bug. > IndexBuildHeapScan() actually does quite a good job of making sure > that HOT chains are sane, which is how the enhanced amcheck notices > the bug here in practice. I think that's too optimistic. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers