Re: [PERFORM] pg_dump and thousands of schemas

On Sun, Sep 2, 2012 at 5:39 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> On Thu, Aug 30, 2012 at 8:17 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>> On Thu, Aug 30, 2012 at 4:51 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>>> Bruce Momjian <bruce(at)momjian(dot)us> writes:
>>>>> On Thu, May 31, 2012 at 09:20:43AM +0900, Tatsuo Ishii wrote:
>>>>>> Ok, I modified the part of pg_dump where tremendous number of LOCK
>>>>>> TABLE are issued. I replace them with single LOCK TABLE with multiple
>>>>>> tables. With 100k tables LOCK statements took 13 minutes in total, now
>>>>>> it only takes 3 seconds. Comments?
>>
>>>>> Was this applied?
>>
>>>> No, we fixed the server side instead.
>>
>>> But only for 9.2, right? So people running back branches are still screwed.
>>
>> Yeah, but they're screwed anyway, because there are a bunch of O(N^2)
>> behaviors involved here, not all of which are masked by what Tatsuo-san
>> suggested.
>
> All of the other ones that I know of were associated with pg_dump
> itself, and since it is recommended to run the newer version of
> pg_dump against the older version of the server, no back patching
> would be necessary to get the benefits of those particular fixes.
>
>> Six months or a year from now, we might have enough confidence in that
>> batch of 9.2 fixes to back-port them en masse. Don't want to do it
>> today though.
>
>
> What would be the recommendation for people trying to upgrade, but who
> can't get their data out in a reasonable window?
>
> Putting Tatsuo-san's change into a future pg_dump might be more
> conservative than back-porting the server's Lock Table change to the
> server version they are trying to get rid of.

What he said.

--
Robert Haas
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