Robert Haas escribió:
> On Wed, Nov 6, 2013 at 9:40 AM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> > Noah Misch wrote:
> >> Incomplete list:
> >>
> >> - If smgrDoPendingDeletes() finds files to delete, mdunlink() and its callee
> >> relpathbackend() call palloc(); this is true in all supported branches. In
> >> 9.3, due to commit 279628a0, smgrDoPendingDeletes() itself calls palloc().
> >> (In fact, it does so even when the pending list is empty -- this is the only
> >> palloc() during a trivial transaction commit.) palloc() failure there
> >> yields a PANIC during commit.
> >
> > I think we should fix this routine to avoid the palloc when not necessary.
> > That initial palloc is pointless.
Here's a trivial patch we could apply to 9.3 immediately. Anything else
such as the ideas proposed below would require more effort than anyone
can probably spend here soon.
> > Also, there have been previous discussions about having relpathbackend
> > not use palloc at all. That was only because we wanted to use it in
> > pg_xlogdump which didn't have palloc support at the time, so it's no
> > longer as pressing; but perhaps it's still worthy of consideration.
>
> +1, but I'd like it better if we could find a way of avoiding the
> palloc in all cases. Panicking because we run out of memory at the
> wrong time isn't really very nice. Maybe the information needs to be
> maintained in the format in which it ultimately needs to be returned,
> so that we needn't rejigger it in the middle of a critical section.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
