From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: andres@anarazel.de
Cc: pgsql-hackers@postgresql.org
Subject: Re: Remove page-read callback from XLogReaderState.
Date: Fri, 12 Jul 2019 16:10:16 +0900 (Tokyo Standard Time)
Message-ID: <20190712.161016.56338282.horikyota.ntt@gmail.com> (raw)
In-Reply-To: <20190528114524.dvj6ymap2virlzro@alap3.anarazel.de>
References: <20190418.210257.43726183.horiguchi.kyotaro@lab.ntt.co.jp>
<20190528114524.dvj6ymap2virlzro@alap3.anarazel.de>
At Tue, 28 May 2019 04:45:24 -0700, Andres Freund <andres@anarazel.de> wrote in <20190528114524.dvj6ymap2virlzro@alap3.anarazel.de>
> Hi,
>
> On 2019-04-18 21:02:57 +0900, Kyotaro HORIGUCHI wrote:
> > Hello. As mentioned before [1], read_page callback in
> > XLogReaderState is a cause of headaches. Adding another
> > remote-controlling stuff to xlog readers makes things messier [2].
> >
> > I refactored XLOG reading functions so that we don't need the
> > callback. In short, ReadRecrod now calls XLogPageRead directly
> > with the attached patch set.
> >
> > | while (XLogReadRecord(xlogreader, RecPtr, &record, &errormsg)
> > | == XLREAD_NEED_DATA)
> > | XLogPageRead(xlogreader, fetching_ckpt, emode, randAccess);
> >
> > On the other hand, XLogReadRecord became a bit complex. The patch
> > makes XLogReadRecord a state machine. I'm not confident that the
> > additional complexity is worth doing. Anyway I'll gegister this
> > to the next CF.
>
> Just FYI, to me this doesn't clearly enough look like an improvement,
> for a change of this size.
Thanks for the opiniton. I kinda agree about size but it is a
decision between "having multiple callbacks called under the
hood" vs "just calling a series of functions". I think the
patched XlogReadRecord is easy to use in many situations.
It would be better if I could completely refactor the function
without the syntax tricks but I think the current patch is still
smaller and clearer than overhauling it.
If many of the folks think that adding a callback is better than
this refactoring, I will withdraw this..
reagrds.
--
Kyotaro Horiguchi
NTT Open Source Software Center
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: horikyota.ntt@gmail.com, andres@anarazel.de
Subject: Re: Remove page-read callback from XLogReaderState.
In-Reply-To: <20190712.161016.56338282.horikyota.ntt@gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox