Re: Contention preventing locking

On 20 February 2018 at 16:07, Konstantin Knizhnik
<k.knizhnik@postgrespro.ru> wrote:
>
>
> On 20.02.2018 14:26, Simon Riggs wrote:
>>
>> Try locking the root tid rather than the TID, that is at least unique
>> per page for a chain of tuples, just harder to locate.
>>
> As far as I understand, it is necessary to traverse the whole page to locate
> root tuple, isn't it?
> If so, then I expect it to be too expensive operation. Scanning the whole
> page on tuple update seems to be not an acceptable solution.

Probably.

It occurs to me that you can lock the root tid in index_fetch_heap().
I hear other DBMS lock via the index.

However, anything you do with tuple locking could interact badly with
heap_update and the various lock modes, so be careful.

You also have contention for heap_page_prune_opt() and with SELECTs to
consider, so I think you need to look at both page and tuple locking.

-- 
Simon Riggs                http://www.2ndQuadrant.com/
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