Re: pg_upgrade should truncate/remove its logs before running

On Sat, Dec 11, 2021 at 08:50:17PM -0600, Justin Pryzby wrote:
> I have seen this numerous times but had not dug into it, until now.
> 
> If pg_upgrade fails and is re-run, it appends to its logfiles, which is
> confusing since, if it fails again, it then looks like the original error
> recurred and wasn't fixed.  The "append" behavior dates back to 717f6d608.
> 
> I think it should either truncate the logfiles, or error early if any of the
> files exist.  Or it could put all its output files into a newly-created
> subdirectory.  Or this message could be output to the per-db logfiles, and not
> just the static ones:
> | "pg_upgrade run on %s".
> 
> For the per-db logfiels with OIDs in their name, changing open() from "append"
> mode to truncate mode doesn't work, since they're written to in parallel.
> They have to be removed/truncated in advance.
> 
> This is one possible fix.  You can test its effect by deliberately breaking one
> of the calls to exec_progs(), like this.
> 
> -  "\"%s/pg_restore\" %s %s --exit-on-error --verbose "
> +  "\"%s/pg_restore\" %s %s --exit-on-error --verboose "

Uh, the database server doesn't erase its logs on crash/failure, so why
should pg_upgrade do that?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.