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Re: Unsplitting btree index leaf pages

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Unsplitting btree index leaf pages
Date: 2005-12-22 22:05:15
Message-ID: 1135289115.2964.530.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, 2005-12-22 at 10:40 -0500, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > Sorry, I missed that. 
> 
> And you evidently still didn't understand it.  Locking both pages does
> not fix the problem, because it doesn't guarantee that there's not a
> concurrent indexscan in flight from one to the other.  If you move items
> from one page to the other in the opposite direction from the way the
> scan is going, then it will miss those items.  If we try to fix this by
> making scans lock one page before releasing the previous, then we'll
> create a bunch of deadlock cases.

Thank you for explaining things; I'm sorry you had to do it twice.

I'm ever optimistic, so I try to resist the temptation to stay quiet in
case I make a mistake.

Best Regards, Simon Riggs



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