On Mon, Feb 6, 2017 at 1:44 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:

> > 2. In the second patch, we tried to recompute attribute lists if a
> relcache
> > flush happens in between and index list is invalidated. We've seen
> problems
> > with that, especially it getting into an infinite loop with
> > CACHE_CLOBBER_ALWAYS. Not clear why it happens, but apparently relcache
> > flushes keep happening.
> Well, yeah: the point of CLOBBER_CACHE_ALWAYS is to make a relcache flush
> happen whenever it possibly could.

Ah, ok. That explains why the retry logic as originally proposed was
causing infinite loop.

> The way to deal with that without
> looping is to test whether the index set *actually* changed, not whether
> it just might have changed.

I like this approach. I'll run the patch on a build with
CACHE_CLOBBER_ALWAYS, but I'm pretty sure it will be ok. I also like the
fact that retry logic is now limited to only when index set changes, which
fits in the situation we're dealing with.


 Pavan Deolasee                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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