Horton

Re: heap vacuum & cleanup locks

Simon Riggs <simon@2ndquadrant.com>

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From: Simon Riggs <simon@2ndQuadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2011-11-08T15:08:53Z
Lists: pgsql-hackers

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  1. Make VACUUM avoid waiting for a cleanup lock, where possible.

On Tue, Nov 8, 2011 at 1:50 PM, Robert Haas <robertmhaas@gmail.com> wrote:

> But there's an efficiency argument against doing it that way.  First,
> if we release the pin then we'll have to reacquire the buffer, which
> means taking and releasing a BufMappingLock, the buffer header
> spinlock, and the buffer content lock.  Second, instead of returning a
> pointer to the data in the page, we'll have to copy the data out of
> the buffer before releasing the pin.

The only way I can see this working is to optimise this in the
planner, so that when we have a nested loop within a loop, we avoid
having the row on the outer loop pinned while we perform the inner
loop.

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
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