Re: Is it possible to change wal_level online

Hi,

On September 14, 2023 6:21:59 AM PDT, Euler Taveira <euler@eulerto.com> wrote:
>On Thu, Sep 14, 2023, at 7:05 AM, Andy Fan wrote:
>> Currently it is complained that wal_level changes require an instance
>> restart,  I'm not familiar with this stuff so far and I didn't get any good
>> information from searching the email archive.  So I want to gather
>> some feedbacks from experts to  see if it is possible and if not, why
>> it would be the key blocker for this.  Basically I agree that changing
>> the wal_level  online will be a good experience for users.
>>
>
>This topic was already discussed. See this thread [1] that was requesting to
>change the wal_level default value. There might be other threads but I didn't
>try hard to find them.
>
>
>[1] https://www.postgresql.org/message-id/20200608213215.mgk3cctlzvfuaqm6%40alap3.anarazel.de

I think it's gotten a bit easier since then, because we now have global barriers, to implement the waiting that's
mentionedin the email. 

Possibly we should do the switch to logical dynamically, without a dedicated wal_level. Whenever a logical slot exists,
automaticallyincrease the Wal level, whenever the last slot is dropped, lower it again. Plus some waiting to ensure
everybackend has knows about the new value.  

Regards,

Andres

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