Re: [COMMITTERS] pgsql: Fix bufmgr so CHECKPOINT_END_OF_RECOVERY behaves as a shutdown c

On Sun, Sep 16, 2012 at 2:54 PM, Simon Riggs <simon@2ndquadrant.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.  Am I missing something?

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.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company