Re: [HACKERS] fsynch of pg_log write..

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От Vadim Mikheev
Тема Re: [HACKERS] fsynch of pg_log write..
Дата
Msg-id 3772EEC3.4F306F77@krs.ru
обсуждение исходный текст
Ответ на fsynch of pg_log write..  (Don Baccus <dhogaza@pacifier.com>)
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Don Baccus wrote:
> 
> FlushBufferPool /* flush and fsync the data blocks */
> TransactionIdCommit /* log the fact that the transaction's done */
> FlushBufferPool /* flush and fsync pg_log and whatever else
>                    has changed during this brief period of time */
> 
> I just added a couple of lines of code that saves
> disableFsync and sets it true before the second call
> to FlushBufferPool, restoring it to its original state
> afterwards.

...

> So...does it sound like I'm doing the right thing?

It's bad in the case of concurrent writes, because of
second FlushBufferPool "flushes whatever else has changed during 
this brief period of time".

Right way is just set some flag in WriteBuffer()/WriteNoReleaseBuffer()
and don't do 

FlushBufferPool
TransactionIdCommit
FlushBufferPool

at all when this flag is not setted.

I'll do it for 6.5.1 if no one else...

Vadim


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