Re: logical decoding : exceeded maxAllocatedDescs for .spill files

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, Alvaro Herrera from 2ndQuadrant <alvherre(at)alvh(dot)no-ip(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, Juan José Santamaría Flecha <juanjo(dot)santamaria(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Subject: Re: logical decoding : exceeded maxAllocatedDescs for .spill files
Date: 2020-01-12 03:53:57
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Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> On Thu, Jan 09, 2020 at 07:40:12PM -0500, Tom Lane wrote:
>> It seems reasonably likely to me that this result is telling us about
>> an actual bug, ie, faulty back-patching of one or more of those fixes
>> into v10 and perhaps earlier branches.

> Well, one thing we did in 11 is introduction of the Generation context.
> In 10 we're still stashing all tuple data into the main AllocSet. I
> wonder if backporting a4ccc1cef5a04cc054af83bc4582a045d5232cb3 and a
> couple of follow-up fixes would make the issue go away.

Hm. I'm loath to back-port Generation contexts. But looking at
a4ccc1cef5a04cc054af83bc4582a045d5232cb3, I see that (a) the
commit message mentions space savings, but (b) the replaced code
in reorderbuffer.c doesn't look like it really would move the needle
much in that regard. The old code had a one-off slab allocator
that we got rid of, but I don't see any actual leak there ...
remind me where the win came from, exactly?

regards, tom lane

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