Re: Block level parallel vacuum WIP

On 1/10/17 11:23 AM, Claudio Freire wrote:
> On Tue, Jan 10, 2017 at 6:42 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>> Does this work negate the other work to allow VACUUM to use >
>>> 1GB memory?
>>
>> Partly yes. Because memory space for dead TIDs needs to be allocated
>> in DSM before vacuum worker launches, parallel lazy vacuum cannot use
>> such a variable amount of memory as that work does. But in
>> non-parallel lazy vacuum, that work would be effective. We might be
>> able to do similar thing using DSA but I'm not sure that is better.
>
> I think it would work well with DSA as well.
>
> Just instead of having a single segment list, you'd have one per worker.
>
> Since workers work on disjoint tid sets, that shouldn't pose a problem.
>
> The segment list can be joined together later rather efficiently
> (simple logical joining of the segment pointer arrays) for the index
> scan phases.

It's been a while since there was any movement on this patch and quite a
few issues have been raised.

Have you tried the approaches that Claudio suggested?

--
-David
david(at)pgmasters(dot)net