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.


Andres Freund

Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:

Reply via email to