Re: Block level parallel vacuum WIP

On Tue, Aug 23, 2016 at 8:02 AM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> 2. Vacuum table and index (after 10000 transaction executed)
>   1 worker   : 12 sec
>   2 workers : 49 sec
>   3 workers : 54 sec
>   4 workers : 53 sec
>
> As a result of my test, since multiple process could frequently try to
> acquire the cleanup lock on same index buffer, execution time of
> parallel vacuum got worse.
> And it seems to be effective for only table vacuum so far, but is not
> improved as expected (maybe disk bottleneck).

Not only that, but from your description (I haven't read the patch,
sorry), you'd be scanning the whole index multiple times (one per
worker).