Re: [HACKERS] Block level parallel vacuum

On Fri, Mar 29, 2019 at 4:53 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Tue, Mar 26, 2019 at 10:31 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > Thank you for reviewing the patch.
>
> I don't think the approach in v20-0001 is quite right.
>
> if (strcmp(opt->defname, "verbose") == 0)
> - params.options |= VACOPT_VERBOSE;
> + params.options |= defGetBoolean(opt) ? VACOPT_VERBOSE : 0;
>
> It seems to me that it would be better to do declare a separate
> boolean for each flag at the top; e.g. bool verbose. Then here do
> verbose = defGetBoolean(opt). And then after the loop do
> params.options = (verbose ? VACOPT_VERBOSE : 0) | ... similarly for
> other options.
>
> The thing I don't like about the way you have it here is that it's not
> going to work well for options that are true by default but can
> optionally be set to false. In that case, you would need to start
> with the bit set and then clear it, but |= can only set bits, not
> clear them. I went and looked at the VACUUM (INDEX_CLEANUP) patch on
> the other thread and it doesn't have any special handling for that
> case, which makes me suspect that if you use that patch, the reloption
> works as expected but VACUUM (INDEX_CLEANUP false) doesn't actually
> succeed in disabling index cleanup. The structure I suggested above
> would fix that.
>

You're right, the previous patches are wrong. Attached the updated
version patches.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center