On Tue, May 12, 2020 at 11:06 PM Peter Geoghegan <p...@bowt.ie> wrote: > try/catch seems like the way to do it. Not all amcheck errors come > from amcheck -- some are things that the backend code does, that are > known to appear in amcheck from time to time. I'm thinking in > particular of the > table_index_build_scan()/heapam_index_build_range_scan() errors, as > well as the errors from _bt_checkpage().
That would require the use of a subtransaction. > You've quasi-duplicated some sensitive code to do that much, which > seems excessive. But it's also not enough. I think this is a good summary of the problems in this area. On the one hand, I think it's hideous that we sanity check user input to death, but blindly trust the bytes on disk to the point of seg faulting if they're wrong. The idea that int4 + int4 has to have overflow checking because otherwise a user might be sad when they get a negative result from adding two negative numbers, while at the same time supposing that the same user will be unwilling to accept the performance hit to avoid crashing if they have a bad tuple, is quite suspect in my mind. The overflow checking is also expensive, but we do it because it's the right thing to do, and then we try to minimize the overhead. It is unclear to me why we shouldn't also take that approach with bytes that come from disk. In particular, using Assert() checks for such things instead of elog() is basically Assert(there is no such thing as a corrupted database). On the other hand, that problem is clearly way above this patch's pay grade. There's a lot of stuff all over the code base that would have to be changed to fix it. It can't be done as an incidental thing as part of this patch or any other. It's a massive effort unto itself. We need to somehow draw a clean line between what this patch does and what it does not do, such that the scope of this patch remains something achievable. Otherwise, we'll end up with nothing. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
