Re: Review: Patch to compute Max LSN of Data Pages

From: Hari Babu <haribabu(dot)kommi(at)huawei(dot)com>
To: "'Andres Freund'" <andres(at)2ndquadrant(dot)com>, "'Amit Kapila'" <amit(dot)kapila(at)huawei(dot)com>
Cc: "'Robert Haas'" <robertmhaas(at)gmail(dot)com>, "'Josh Berkus'" <josh(at)agliodbs(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Review: Patch to compute Max LSN of Data Pages
Date: 2013-07-08 11:55:21
Message-ID: 01ca01ce7bd2$0688cba0$139a62e0$@kommi@huawei.com
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On Monday, July 08, 2013 5:16 PM Andres Freund wrote:
>On 2013-07-08 17:10:43 +0530, Amit Kapila wrote:
>> On Monday, July 08, 2013 4:26 PM Andres Freund wrote:
>> > On 2013-07-08 16:17:54 +0530, Hari Babu wrote:
>> > > + This utility can also be used to decide whether backup is
>> > required or not when the data page
>> > > + in old-master precedes the last applied LSN in old-standby
>> > (i.e., new-master) at the
>> > > + moment of the failover.
>> > > + </para>
>> > > + </refsect1>
>> >
>> > I don't think this is safe in any interesting set of cases. Am I
>> > missing
>> > something?
>>
>> No, you are not missing anything. It can be only used to find max LSN in
>> database which can avoid further corruption

>Why is the patch submitted documenting it as a use-case then? I find it
>rather scary if the *patch authors* document a known unsafe use case as
>one of the known use-cases.

I got the problem which can occur with the specified use case. Removed the
wrong use case specified above.
Thanks for the review, please find the updated patch attached in the mail.

Regards,
Hari babu.

Attachment Content-Type Size
pg_computemaxlsn_v10.patch application/octet-stream 16.9 KB

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