From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
Cc: | David Gilman <davidgilman1(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: "tuple concurrently updated" in pg_restore --jobs |
Date: | 2020-07-11 17:11:26 |
Message-ID: | 2393679.1594487486@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Justin Pryzby <pryzby(at)telsasoft(dot)com> writes:
> On Fri, Jul 10, 2020 at 05:36:28PM -0400, Tom Lane wrote:
>> I'm not sure how far to back-patch it -- I think the parallel restore
>> of ACLs behavior is not very old, but we might want to teach older
>> pg_dump versions to insert the extra dependency anyway, for safety.
> Yes, and the test case in David's patch on other thread [0] can't be
> backpatched further than this patch is.
Actually, the answer seems to be that we'd better back-patch all the way,
because this is a live bug much further back than I'd guessed. pg_restore
is willing to run these ACL restores in parallel in all active branches.
The given test case only shows a failure back to 9.6, because older
versions don't dump ACLs on system catalogs; but of course you can just
try it with a user table instead.
Oddly, I could not get the "tuple concurrently updated" syndrome to
appear on 9.5. Not sure why not; the GRANT/REVOKE code looks the
same as in 9.6. What I *could* demonstrate in 9.5 is that sometimes
the post-restore state is flat out wrong: the column-level grants go
missing, presumably as a result of the table-level REVOKE executing
after the column-level GRANTs. Probably that syndrome occurs sometimes
in later branches too, depending on timing; but I didn't look.
regards, tom lane
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