Re: foreign key locks, 2nd attempt

Excerpts from Bruce Momjian's message of jue nov 10 16:59:20 -0300 2011:
> Alvaro Herrera wrote:
> > Hello,
> > 
> > After some rather extensive rewriting, I submit the patch to improve
> > foreign key locks.
> > 
> > To recap, the point of this patch is to introduce a new lock tuple mode,
> > that lets the RI code obtain a lighter lock on tuples, which doesn't
> > conflict with updates that do not modify the key columns.
> 
> What kind of operations benefit from a non-key lock like this?

I'm not sure I understand the question.

With this patch, a RI check does "SELECT FOR KEY SHARE".  This means the
tuple is locked with that mode until the transaction finishes.  An
UPDATE that modifies the referenced row will not conflict with that lock.

An UPDATE that modifies the key columns will be blocked, just as now.
Same with a DELETE.

-- 
Álvaro Herrera 
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