Re: [HACKERS] fsynch of pg_log write.. - Mailing list pgsql-hackers

From Vadim Mikheev
Subject Re: [HACKERS] fsynch of pg_log write..
Date
Msg-id 3772EEC3.4F306F77@krs.ru
Whole thread Raw
In response to fsynch of pg_log write..  (Don Baccus <dhogaza@pacifier.com>)
List pgsql-hackers
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


pgsql-hackers by date:

Previous
From: Vadim Mikheev
Date:
Subject: Re: [HACKERS] The dangers of "-F"
Next
From: Edmund Mergl
Date:
Subject: Re: [HACKERS] Perl 5 Interface on 6.5 and lo_creat/lo_open problem