Re: INSERT...ON DUPLICATE KEY LOCK FOR UPDATE

On 2013-12-26 21:11:27 -0800, Peter Geoghegan wrote:
> I'm generally opposed to making value locks of any stripe be held for
> more than an instant (so we should not hold them indefinitely pending
> another conflicting xact finishing). It's not just that it's
> convenient to my implementation; I also happen to think that it makes
> no sense. Should you really lock a value in an earlier unique index
> for hours, pending conflicter xact finishing, because you just might
> happen to want to insert said value, but probably not?

There are some advantages: For one, it allows you to guarantee forward
progress if you do it right, which surely isn't a bad propert to
have. For another, it's much more in line with the way normal uniqueness
checks works.
Possibly the disadvantages outweigh the advantages, but that's a far cry
from making no sense.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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