Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple

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От Peter Geoghegan
Тема Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple
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Msg-id CAH2-Wzmscv3DYDtOLjOSrzv9khMr4LR=UFGeFvOWBMG-U1DpyQ@mail.gmail.com
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Ответ на Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updatedtuple  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Ответы Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updatedtuple  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Список pgsql-hackers
On Thu, Sep 28, 2017 at 1:20 PM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> Alvaro Herrera wrote:
>
>> Odd that it's not fixed.  I guess there's still some more work to do
>> here ...
>
> Maybe what this means is that we need to do both Dan's initially
> proposed patch (or something related to it) apart from the fixes already
> pushed.  IOW we need to put back some of the "tupkeep" business ...

We certainly do still see wrong answers to queries here:

postgres=# select ctid, xmin, xmax, * from t;ctid  | xmin  | xmax | id | name | x
-------+-------+------+----+------+---(0,1) | 21171 |    0 |  1 | 111  | 0(0,7) | 21177 |    0 |  3 | 333  | 5
(2 rows)

postgres=# select * from t where id = 3;id | name | x
----+------+--- 3 | 333  | 5
(1 row)

postgres=# set enable_seqscan = off;
SET
postgres=# select * from t where id = 3;id | name | x
----+------+---
(0 rows)

FWIW, I am reminded a little bit of the MultiXact/recovery bug I
reported way back in February of 2014 [1], which also had a HOT
interaction that caused index scans to give wrong answers, despite
more or less structurally sound indexes.

[1] https://www.postgresql.org/message-id/CAM3SWZTMQiCi5PV5OWHb+bYkUcnCk=O67w0cSswPvV7XfUcU5g@mail.gmail.com

-- 
Peter Geoghegan


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