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From: Achilleas Mantzios <[email protected]>
To: [email protected]
Subject: Re: Strange deadlock with object/target of lock : transaction
Date: Wed, 20 Aug 2025 14:59:05 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On 8/14/25 16:01, Achilleas Mantzios wrote:

> Hi Adrian
>
> On 8/14/25 15:39, Adrian Klaver wrote:
>
>> On 8/14/25 00:07, Achilleas Mantzios wrote:
>>> Hi All
>>>
>>> We've been hit by a weird deadlock which it took me some days to 
>>> isolate and replicate. It does not have to do with order of updates 
>>> or any explicit TABLE-level locking, the objects/targets of the 
>>> deadlock in question are transactions.
>>
> First off, I maybe wrong with the above conclusion, I noticed that 
> even in the common deadlock scenario (xact A updating object 1 and 
> then 2, while xact B updating 2 and then 1) the message is again the 
> same , i.e.
>
> Process <pid1> waits for ShareLock on transaction <xactB>; blocked by 
> process <pid2>.
>
> Process <pid2> waits for ShareLock on transaction <xactA>; blocked by 
> process <pid1>.
>
> while updating tuple ()...
>
> Also I should have mentioned that it takes at least three transactions 
> as in the example to make the deadlock happen. At least two of the 
> "UPDATE" style and one of the "INSERT" style.
>
>> I have some questions:
>>
>> 1) Did this work in versions prior to 18?
> No, our production is on 16.9 and this is where I got the issue.
>>
>> 2) The test case you ran was done on 18beta1, are you planning to 
>> test on the just released 18beta3?
> I must upgrade, but I don't think anything will change, this behavior 
> seems consistent at least across 16->18beta1
Hi, I just tested with 18beta3, as expected, no change at all, I still 
get the deadlock.
>>
>>

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