Re: Implement waiting for wal lsn replay: reloaded

From: Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>
To: pgsql-hackers(at)lists(dot)postgresql(dot)org, Alexander Korotkov <aekorotkov(at)gmail(dot)com>
Subject: Re: Implement waiting for wal lsn replay: reloaded
Date: 2025-02-28 13:55:21
Message-ID: fb9535e7-0081-4a02-8b21-dd5edd82e7c4@postgrespro.ru
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28.02.2025 16:03, Yura Sokolov пишет:
> 17.02.2025 00:27, Alexander Korotkov wrote:
>> On Thu, Feb 6, 2025 at 10:31 AM Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru> wrote:
>>> I briefly looked into patch and have couple of minor remarks:
>>>
>>> 1. I don't like `palloc` in the `WaitLSNWakeup`. I believe it wont issue
>>> problems, but still don't like it. I'd prefer to see local fixed array, say
>>> of 16 elements, and loop around remaining function body acting in batch of
>>> 16 wakeups. Doubtfully there will be more than 16 waiting clients often,
>>> and even then it wont be much heavier than fetching all at once.
>>
>> OK, I've refactored this to use static array of 16 size. palloc() is
>> used only if we don't fit static array.
>
> I've rebased patch and:
> - fixed compiler warning in wait.c ("maybe uninitialized 'result'").
> - made a loop without call to palloc in WaitLSNWakeup. It is with "goto" to
> keep indentation, perhaps `do {} while` would be better?

And fixed:
'WAIT' is marked as BARE_LABEL in kwlist.h, but it is missing from
gram.y's bare_label_keyword rule

-------
regards
Yura Sokolov aka funny-falcon

Attachment Content-Type Size
v4-0001-Implement-WAIT-FOR-command.patch text/x-patch 46.0 KB

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