Re: max_standby_delay considered harmful

On Mon, 2010-05-03 at 13:21 -0400, Robert Haas wrote:
> On Mon, May 3, 2010 at 11:37 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > I'm inclined to think that we should throw away all this logic and just
> > have the slave cancel competing queries if the replay process waits
> > more than max_standby_delay seconds to acquire a lock.
> 
> What if we somehow get into a situation where the replay process is
> waiting for a lock over and over and over again, because it keeps
> killing conflicting processes but something restarts them and they
> take locks over again?  It seems hard to ensure that replay will make
> adequate progress with any substantially non-zero value of
> max_standby_delay under this definition.

That is one argument against, and a reason why just one route is bad.

We already have more than one way, so another option is useful

-- Simon Riggs           www.2ndQuadrant.com