Re: heap vacuum & cleanup locks

On Tue, Nov 8, 2011 at 1:50 PM, Robert Haas  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/
 PostgreSQL Development, 24x7 Support, Training & Services