Re: vacuumdb -f and -j options (was Question / requests.)

On Sat, Oct 8, 2016 at 9:12 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Fri, Oct 7, 2016 at 10:16 PM, Alvaro Herrera
> <alvherre(at)2ndquadrant(dot)com> wrote:
>> Robert Haas wrote:
>>> On Wed, Oct 5, 2016 at 10:58 AM, Francisco Olarte
>>> I don't know, but it seems like the documentation for vacuumdb
>>> currently says, more or less, "Hey, if you use -j with -f, it may not
>>> work!", which seems unacceptable to me. It should be the job of the
>>> person writing the feature to make it work in all cases, not the job
>>> of the person using the feature to work around the problem when it
>>> doesn't.
>>
>> The most interesting use case of vacuumdb is lazy vacuuming, I think, so
>> committing that patch as it was submitted previously was a good step
>> forward even if it didn't handle VACUUM FULL 100%.
>>
>> I agree that it's better to have both modes Just Work in parallel, which
>> is the point of this subsequent patch. So let's move forward. I
>> support Francisco's effort to make -f work with -j. I don't have a
>> strong opinion on which of the various proposals presented so far is the
>> best way to implement it, but let's figure that out and get it done.
>>
>
> After reading Francisco's proposal [1], I don't think it is directly
> trying to make -f and -j work together. He is proposing to make it
> work by providing some new options. As you are wondering upthread, I
> think it seems reasonable to disallow -f with parallel vacuuming if no
> tables are specified.

Instead of restricting completely things, I'd like to think that being
able to make both of them work together is the right move at the end.
From what I recall from the code of vacuumdb, I agree with Alvaro's
position: it would not be much a complicated challenge to vacuum all
the catalogs in one worker and spread the rest of the tables in the
rest of them. We need to be careful of the case where a list of tables
is given by the user via -t though, in the case where user is passing
both catalog and normal relations.
--
Michael