On Thu, Jun 9, 2022 at 09:46:51AM -0700, Mark Dilger wrote: > > > > On Jun 8, 2022, at 5:45 AM, Bruce Momjian <br...@momjian.us> wrote: > > > > Is this something anyone has even needed or had requested? > > I might have put this in amcheck's verify_heapam() had there been an > interface for it. I vaguely recall wanting something like this, yes. > > As it stands, verify_heapam() may trigger mdread()'s "could not open > file" or "could not read block" error, in the course of verifying > the table. There isn't an option in amcheck to just verify that > the underlying files exist. If struct f_smgr had a function for > validating that all segment files exist, I may have added an option to > amcheck (and the pg_amcheck frontend tool) to quickly look for missing > files.
Well, how do we know what files should exist? We know the first segment should probably exist, but what about +1GB segments? > Looking at smgr/md.c, it seems mdnblocks() is close to what we want, > but it skips already opened segments "to avoid redundant seeks". > Perhaps we'd want to add a function to f_smgr, say "smgr_allexist", > to check for all segment files? I'm not sure how heavy-handed the > corresponding mdallexist() function should be. Should it close > all open segments, then reopen and check the size of all of them > by calling mdnblocks()? That seems safer than merely asking the > filesystem if the file exists without verifying that it can be opened. Yes. > If we made these changes, and added corresponding quick check options > to amcheck and pg_amcheck, would that meet your current needs? The > downside to using amcheck for this sort of thing is that we did not > (and likely will not) back port it. I have had several occasions to > want this functionality recently, but the customers were on pre-v14 > servers, so these tools were not available anyway. I don't have a need for it --- I was just wondering why we have something that checks the relation contents, but not the file existence? It seems like pg_amcheck would be a nice place to add this checking ability. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Indecision is a decision. Inaction is an action. Mark Batterson
