|From:||"Bossart, Nathan" <bossartn(at)amazon(dot)com>|
|To:||Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>|
|Cc:||Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Lyes Ameddah <lyes(dot)amd(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, "pgsql-bugs(at)postgresql(dot)org" <pgsql-bugs(at)postgresql(dot)org>|
|Subject:||Re: BUG #14941: Vacuum crashes|
|Views:||Raw Message | Whole Thread | Download mbox|
Thanks for taking a look.
On 3/3/18, 6:13 PM, "Andres Freund" <andres(at)anarazel(dot)de> wrote:
> I was working on committing 0002 and 0003, when I noticed that the
> second patch doesn't actually fully works. NOWAIT does what it says on
> the tin iff the table is locked with a lower lock level than access
> exclusive. But if AEL is used, the command is blocked in
> static List *
> expand_vacuum_rel(VacuumRelation *vrel)
> * We transiently take AccessShareLock to protect the syscache lookup
> * below, as well as find_all_inheritors's expectation that the caller
> * holds some lock on the starting relation.
> relid = RangeVarGetRelid(vrel->relation, AccessShareLock, false);
> ISTM has been added after the patches initially were proposed. See
> I'm a bit disappointed that the tests didn't catch this, they're clearly
> not fully there. They definitely should test the AEL case, as
> demonstrated here.
Sorry about that. I've added logic to handle ACCESS EXCLUSIVE in v6 of 0002,
and I've extended the tests to cover that case.
> Independent of that, I'm also concerned that NOWAIT isn't implemented
> consistently with other commands. Aren't we erroring out in other uses
> of NOWAIT? ISTM a more appropriate keyword would have been SKIP
> LOCKED. I think the behaviour makes sense, but I'd rename the internal
> flag and the grammar to use SKIP LOCKED.
Agreed. I've updated 0002 to use SKIP LOCKED instead of NOWAIT.
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