From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [COMMITTERS] pgsql: Fix bufmgr so CHECKPOINT_END_OF_RECOVERY behaves as a shutdown c |
Date: | 2012-09-17 21:04:18 |
Message-ID: | CA+U5nM+U6tEj2YrFr1i5FobbyAyFUD5-jWkupCpUtRVrtRhMYA@mail.gmail.com |
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On 17 September 2012 15:59, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sun, Sep 16, 2012 at 2:54 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> Fix bufmgr so CHECKPOINT_END_OF_RECOVERY behaves as a shutdown checkpoint.
>> Recovery code documents clearly that a shutdown checkpoint is executed at
>> end of recovery - a shutdown checkpoint WAL record is written but the buffer
>> manager had been altered to treat end of recovery as a normal checkpoint.
>> This bug exacerbates the bufmgr relpersistence bug.
>>
>> Bug spotted by Andres Freund, patch by me.
>
> I am confused by this patch. It seems to me that the effect of this
> patch is to force unlogged buffers to be written at end-of-recovery as
> well as at shutdown. But, barring bugs elsewhere, there shouldn't be
> any unlogged buffers in shared_buffers at end-of-recovery, so this
> won't make any difference at all.
There shouldn't be, but this coding is the fail safe way.
> Am I missing something?
If you or others do, this will save us.
> Maybe what we should do is - if this is an end-of-recovery checkpoint
> - *assert* that the BM_PERMANENT bit is set on every buffer we find.
> That would provide a useful cross-check that we don't have a bug
> similar to the one Jeff already fixed in any other code path.
Safety net is needed there, not an Assert.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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