From: | Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> |
---|---|
To: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
Cc: | 757634191(at)qq(dot)com, japinli(at)hotmail(dot)com, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: 回复: Why is XLOG_FPI_FOR_HINT always need backups? |
Date: | 2021-07-16 15:14:34 |
Message-ID: | 652d0e28-28f2-44e5-5b97-5f38bd976290@oss.nttdata.com |
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Lists: | pgsql-hackers |
On 2021/07/16 16:31, Kyotaro Horiguchi wrote:
> Sorry, I missed that the XLogReadBufferForRedo is expected to return
> BLK_RESTORED. And XLogReadBufferForRedo errors out when it tries to
> read nonexistent page without having an FPI (this happens for FSM
> pages). Rather than teaching XLogReadBufferExtended to behave
> differrently for the case, I choosed to avoid trying to load the page
> when the corresponding FPI block is missing in XLOG_FPI_FOR_HINT, as
> if the record itself did not exist at all.
>
> Since differently from XLOG_FPI, XLOG_FPI_FOR_HINT has only one page
> reference at most, but in the attached the decision whether to read
> the page or not is made for each block.
Thanks for updating the patch! It basically looks good to me.
* Full-page image (FPI) records contain nothing else but a backup
* block (or multiple backup blocks). Every block reference must
* include a full-page image - otherwise there would be no point in
* this record.
The above comment also needs to be updated?
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
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