Date: Tue, 19 May 2020 08:07:40 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: David Gilman <davidgilman1@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Warn when parallel restoring a custom dump without data offsets
Message-ID: <20200519130740.GO18456@telsasoft.com>
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On Sat, May 16, 2020 at 04:57:46PM -0400, David Gilman wrote:
> If pg_dump can't seek on its output stream when writing a dump in the
> custom archive format (possibly because you piped its stdout to a file)
> it can't update that file with data offsets. These files will often
> break parallel restoration. Warn when the user is doing pg_restore on
> such a file to give them a hint as to why their restore is about to
> fail.

You didn't say so, but I gather this is related to this other thread (which
seems to represent two separate issues).
https://www.postgresql.org/message-id/flat/1582010626326-0.post%40n3.nabble.com#0891d77011cdb6ca3ad8ab7904a2ed63

> Tom, if you or anyone else with PostgreSQL would appreciate the
> pg_dump file I can send it to you out of band, it's only a few
> megabytes. I have pg_restore with debug symbols too if you want me to
> try anything.

Would you send to me or post a link to a filesharing site and I'll try to
reproduce it ?  So far no luck.

You should include here your diagnosis from that thread, or add it to a commit
message, and mention the suspect commit (548e50976).  Eventually add patch for
the next commitfest.  https://commitfest.postgresql.org/

I guess you're also involved in this conversation:
https://dba.stackexchange.com/questions/257398/pg-restore-with-jobs-flag-results-in-pg-restore-error-a-worker-process-di

-- 
Justin