Re: [bug fix] Memory leak in dblink

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On 06/18/2014 08:50 PM, Joe Conway wrote:
> On 06/18/2014 08:45 PM, Tom Lane wrote:
>> Well, we usually think memory leaks are back-patchable bugs. I'm
>> a bit worried about the potential performance impact of an extra
>> memory context creation/deletion though. It's probably not
>> noticeable in this test case, but that's just because dblink()
>> is such a spectacularly expensive function.
>
> Probably so. I'll try to scrounge up some time to test the
> performance impact of your patch.

Not the most scientific of tests, but I think a reasonable one:

8<-----------
create function testcontext(arg int) returns setof int as
$$select $1$$ language sql;

do $$
declare
i int;
rec record;
begin
for i in 1..1000000 loop
select * into rec from testcontext(42);
end loop;
end
$$;
8<-----------

I threw out the first run (not shown) in each group below.

without patch
- -------------
Time: 9930.320 ms
Time: 9963.114 ms
Time: 10048.067 ms
Time: 9899.810 ms
Time: 9926.066 ms
Time: 9996.044 ms
Time: 9919.095 ms
Time: 9921.482 ms
Time: 9904.839 ms
Time: 9990.285 ms
=================
Avg: 9949.912 ms

with patch
- -------------
Time: 10172.148 ms
Time: 10203.585 ms
Time: 10142.779 ms
Time: 10211.159 ms
Time: 10109.001 ms
Time: 10216.619 ms
Time: 10221.820 ms
Time: 10153.220 ms
Time: 10147.540 ms
Time: 10176.478 ms
==================
Avg: 10175.435 ms

without patch
- -------------
Time: 9897.838 ms
Time: 9848.947 ms
Time: 9830.405 ms
Time: 9824.837 ms
Time: 9828.743 ms
Time: 9990.998 ms
Time: 9820.717 ms
Time: 9853.545 ms
Time: 9850.613 ms
Time: 9836.452 ms
=================
Avg: 9858.310 ms

2.7% performance penalty

Joe

- --
Joe Conway
credativ LLC: http://www.credativ.us
Linux, PostgreSQL, and general Open Source
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