From: | Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> |
---|---|
To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Amit Kapila <amit(dot)kapila(at)enterprisedb(dot)com>, Andres Freund <andres(at)anarazel(dot)de> |
Subject: | Re: WAL consistency check facility |
Date: | 2016-11-03 09:48:51 |
Message-ID: | CAGz5QCL3zfdPqDqoVfyk8=M94A2v6tv3WvprOK0P6MSkDO94Sw@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Thu, Nov 3, 2016 at 2:52 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Thu, Nov 3, 2016 at 6:15 PM, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
>> Actually, I just verified that bimg_info is not even valid if
>> has_image is not set.
>> In DecodeXLogRecord, we initialize bimg_info only when has_image flag
>> is set. So, keeping them
>> separate doesn't look a good approach to me. If we keep them separate,
>> the output
>> of the following assert is undefined:
>> Assert(XLogRecHasBlockImage(record, block_id) ||
>> !XLogRecBlockImageApply(record, block_id)).
>>
>> Thoughts??
>
> Yes, that's exactly the reason why we should keep both macros as
> checking for separate things: apply implies that has_image is set and
> that's normal, hence we could use sanity checks by just using those
> macros and not propagating xlogreader.h.
>
No, apply doesn't mean has_image is set. If has_image is not set,
apply/bimg_info
is invalid(/undefined) and we should not use that. For example, in
XLogDumpDisplayRecord we use
bimg_info as following,
if (XLogRecHasBlockImage(record, block_id))
{
if (record->blocks[block_id].bimg_info & BKPIMAGE_IS_COMPRESSED)
{
}
}
So, whenever we are required to use bimg_info flag, we should make
sure that has_image
is set.
--
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com
From | Date | Subject | |
---|---|---|---|
Next Message | amul sul | 2016-11-03 09:49:43 | Re: Remove the comment on the countereffectiveness of large shared_buffers on Windows |
Previous Message | Michael Paquier | 2016-11-03 09:22:58 | Re: WAL consistency check facility |