From: Amit Kapila <amit.kapila@huawei.com>
To: "'Jim Nasby'" <jim@nasby.net>, "'Greg Smith'" <greg@2ndQuadrant.com>
CC: "'PostgreSQL-development'" <pgsql-hackers@postgreSQL.org>
References: <002f01ce50a8$e057c7a0$a10756e0$@kapila@huawei.com>
	<51928CDA.7030009@2ndQuadrant.com> <519E873D.5000406@nasby.net>
In-Reply-To: <519E873D.5000406@nasby.net>
Subject: Re: Move unused buffers to freelist
Date: Fri, 24 May 2013 12:25:29 +0530
Message-ID: <006001ce584b$adfc55f0$09f501d0$@kapila@huawei.com>
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On Friday, May 24, 2013 2:47 AM Jim Nasby wrote:
> On 5/14/13 2:13 PM, Greg Smith wrote:
> > It is possible that we are told to put something in the freelist that
> > is already in it; don't screw up the list if so.
> >
> > I don't see where the code does anything to handle that though.  What
> was your intention here?
> 
> IIRC, the code that pulls from the freelist already deals with the
> possibility that a block was on the freelist but has since been put to
> use. 

You are right, the check exists in StrategyGetBuffer()

>If that's the case then there shouldn't be much penalty to adding
> a block multiple times (at least within reason...)

There is a check in StrategyFreeBuffer() which will not allow to put
multiple times, 
I had just used the same check in new function.

With Regards,
Amit Kapila.


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