Обсуждение: compute_index_stats is missing a CHECK_FOR_INTERRUPTS
Analyze on functional indexes cannot be interrupted very easily.
Example:
create language plperl;
create table foo1 as select x::text from generate_series(1,1000) foo (x);
create table foo2 as select reverse(x) from foo1;
--use a fast version to set up the demo, as we are impatient
CREATE or replace FUNCTION slow_reverse(text) RETURNS text
LANGUAGE plperl IMMUTABLE STRICT COST 1000000
AS $_X$
return reverse($_[0]);
$_X$;
create index on foo2 (slow_reverse(reverse));
analyze foo2;
--put the slow version in place.
CREATE or replace FUNCTION slow_reverse(text) RETURNS text
LANGUAGE plperl IMMUTABLE STRICT COST 1000000
AS $_X$
my $foo; foreach (1..1e6) {$foo+=sqrt($_)};
return reverse($_[0]);
$_X$;
-- now spring the trap
analyze foo2;
Ctrl-C (or pg_ctl stop -mf) hangs for a long time.
The attached patch fixes it, but don't vouch for its safety.
I believe I've seen a real-world example of this causing refusal of a fast shutdown to shutdown fast.
Cheers,
Jeff
Вложения
Jeff Janes <jeff.janes@gmail.com> writes:
> Analyze on functional indexes cannot be interrupted very easily.
> ...
> The attached patch fixes it, but don't vouch for its safety.
Hm. The other per-sample-row loops in analyze.c use vacuum_delay_point()
rather than CHECK_FOR_INTERRUPTS() directly. Ordinarily that wouldn't
make much difference here, but maybe a slow index function might be
incurring I/O?
regards, tom lane
On Sat, Mar 28, 2015 at 3:37 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Jeff Janes <jeff.janes@gmail.com> writes:
> Analyze on functional indexes cannot be interrupted very easily.
> ...
> The attached patch fixes it, but don't vouch for its safety.
Hm. The other per-sample-row loops in analyze.c use vacuum_delay_point()
rather than CHECK_FOR_INTERRUPTS() directly. Ordinarily that wouldn't
make much difference here, but maybe a slow index function might be
incurring I/O?
That isn't the case for me (and if it were, they wouldn't be going through the buffer manager anyway and so would not trigger delay criteria), but that seems like a valid concern in general. It also explains why I couldn't find CHECK_FOR_INTERRUPTS in other loops of that file, because I was looking for the wrong spelling.
Adding a vacuum_delay_point does solve the immediately observed problem, both the toy one and the more realistic one.
Thanks,
Jeff
Вложения
Jeff Janes <jeff.janes@gmail.com> writes:
> On Sat, Mar 28, 2015 at 3:37 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Hm. The other per-sample-row loops in analyze.c use vacuum_delay_point()
>> rather than CHECK_FOR_INTERRUPTS() directly. Ordinarily that wouldn't
>> make much difference here, but maybe a slow index function might be
>> incurring I/O?
> That isn't the case for me (and if it were, they wouldn't be going through
> the buffer manager anyway and so would not trigger delay criteria), but
> that seems like a valid concern in general. It also explains why I
> couldn't find CHECK_FOR_INTERRUPTS in other loops of that file, because I
> was looking for the wrong spelling.
> Adding a vacuum_delay_point does solve the immediately observed problem,
> both the toy one and the more realistic one.
Committed, thanks.
regards, tom lane