Date: Wed, 11 Jun 2025 15:45:46 +0200
From: Christoph Berg <myon@debian.org>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>,
	Andres Freund <andres@anarazel.de>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: CHECKPOINT unlogged data
Message-ID: <aEmIijETyhj9DsWG@msg.df7cb.de>
References: <vp4cewuyo2cw4fk5sxjaovllhe3dscixxo2utu3cgqhzydrqec@wc2nhgx4khpk>
 <aDnl5N1u7UBYVaSt@nathan>
 <aDnpeJ99HhoMgJ40@msg.df7cb.de>
 <7x6gsmev36zzh6lfzydkddbhpnxqgu2k2l2ci2k6foxhrstvj2@bn55g54wjrl4>
 <aEK88AwaYBNK1p-O@msg.df7cb.de>
 <fc1ed66f-e95a-4d10-a4f7-7fa4bb9a7084@oss.nttdata.com>
 <aEL6sDr9RxdSkPm-@msg.df7cb.de>
 <aEMIrLUDOKgmE_0P@nathan>
 <aEMVRbmqqg-aaxAN@msg.df7cb.de>
 <aEMYYEkQb2VeQoBo@nathan>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <aEMYYEkQb2VeQoBo@nathan>
Archived-At: 
 <https://www.postgresql.org/message-id/aEmIijETyhj9DsWG%40msg.df7cb.de>
Precedence: bulk

Re: Nathan Bossart
> That seems like a good idea to me.  I'm tempted to say that "fast" more
> accurately describes what's happening than "immediate."  "Immediate" sounds
> like it happens instantaneously, but it's actually just happening "fast,"
> i.e., as fast as possible.

Ack.

> > #define CHECKPOINT_FLUSH_ALL    0x0010  /* Flush all pages, including those
> >                                          * belonging to unlogged tables */
> > 
> > Maybe CHECKPOINT_FLUSH_UNLOGGED would be more explicit?
> 
> WFM.

Do we want to change the checkpoint log message (and the new options)
only, or include the CHECKPOINT_* flags? (I would guess there aren't
many external users of these flags, but mmmv.)

> I thought it would make sense to put it closer to where these options are
> described, since it'll be most evident for manually-initiated checkpoints.

Ack, I'll add that.

> >> We might also want to make sure it's clear that CHECKPOINT does nothing if
> >> there's been no database activity since the last one (or, in the case of a
> >> restartpoint, if there hasn't been a checkpoint record).
> > 
> > That's taken care of by "force":
> > 
> > #define CHECKPOINT_FORCE        0x0008  /* Force even if no activity */
> 
> Oh, I see that we always specify that for CHECKPOINT commands, except for
> restartpoints.  IIRC even if you do specify CHECKPOINT_FORCE for a
> restartpoint, it'll have no effect.  It's proably worth mentioning that
> case, at least.

Right, will do.

Christoph