| 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 04:20:56 |
| Message-ID: | 7490.1578802856@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> On Sat, Jan 11, 2020 at 10:53:57PM -0500, Tom Lane wrote:
>> remind me where the win came from, exactly?
> Well, the problem is that in 10 we allocate tuple data in the main
> memory ReorderBuffer context, and when the transaction gets decoded we
> pfree() it. But in AllocSet that only moves the data to the freelists,
> it does not release it entirely. So with the right allocation pattern
> (sufficiently diverse chunk sizes) this can easily result in allocation
> of large amount of memory that is never released.
> I don't know if this is what's happening in this particular test, but I
> wouldn't be surprised by it.
Nah, don't think I believe that: the test inserts a bunch of tuples,
but they look like they will all be *exactly* the same size.
CREATE TABLE decoding_test(x integer, y text);
...
FOR i IN 1..10 LOOP
BEGIN
INSERT INTO decoding_test(x) SELECT generate_series(1,5000);
EXCEPTION
when division_by_zero then perform 'dummy';
END;
regards, tom lane
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