Re: Is there a way (except from server logs) to know the kind of on-going/last checkpoint?

On 12/8/21 02:54, Bharath Rupireddy wrote:
> On Wed, Dec 8, 2021 at 4:07 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
>>> I'd bet squashing all of this into a single string (not really a flag)
>>> will just mean people will have to parse it, etc. Keeping individual
>>> boolean flags (or even separate string fields) would be better, I guess.
>>
>> Since the size of controldata is a concern, I suggest to add an int16 to
>> populate with flags, which pg_controldata can parse for display.
> 
> +1. I will come up with a patch soon.
> 
>> Note that this other patch intends to add the timestamp and LSN of most recent
>> recovery to controldata.
>> https://commitfest.postgresql.org/36/3183/
> 
> Thanks. I will go through it separately.
> 
>>> We already have some checkpoint info in pg_stat_bgwriter, but that's
>>> just aggregated data, not very convenient for info about the current
>>> checkpoint. So maybe we should add pg_stat_progress_checkpoint, showing
>>> various info about the current checkpoint?
>>
>> It could go into the pg_stat_checkpointer view, which would be the culmination
>> of another patch (cc Melanie).
>> https://commitfest.postgresql.org/36/3272/
> 

I don't think the pg_stat_checkpointer would be a good match - that's
going to be an aggregated view of all past checkpoints, not a good
source info about the currently running one.

> +1 to have pg_stat_progress_checkpoint view. We have
> CheckpointStatsData already. What we need is to make this structure
> shared and add a little more info to represent the progress, so that
> the other backends can access it. I think we can discuss this in a
> separate thread to give it a fresh try rather than proposing this as a
> part of another thread. I will spend some time on
> pg_stat_progress_checkpoint proposal and try to come up with a
> separate thread to discuss.
> 

+1 to discuss it as part of this patch

I'm not sure whether the view should look at CheckpointStatsData, or do
the same thing as the other pg_stat_progress_* views - send the data to
stat collector, and read it from there.


regards

-- 
Tomas Vondra
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