Re: [HACKERS] [Proposal] Allow users to specify multiple tables inVACUUM commands

On Thu, May 11, 2017 at 11:13 AM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> On Thu, May 11, 2017 at 6:40 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> "Bossart, Nathan" <bossartn@amazon.com> writes:
>>> Currently, VACUUM commands allow you to specify one table or all of the tables in the current database to vacuum.
I’verecently found myself wishing I could specify multiple tables in a single VACUUM statement.  For example, this
wouldbe convenient when there are several large tables in a database and only a few need cleanup for XID purposes.  Is
thisa feature that the community might be interested in? 
>>
>> I'm a bit surprised to realize that we don't allow that, since the
>> underlying code certainly can do it.
>>
>> You realize of course that ANALYZE should grow this capability as well.
>
> Yup. It is just a matter of extending ExecVacuum() to handle a list of
> qualified names with a quick look at the grammar as we are talking
> only about manual commands. One question I am wondering though is do
> we want to have everything happening in the same transaction? I would
> say yes to that to simplify the code. I think that VERBOSE should also
> report the per-table information, so this can be noisy with many
> tables but that's more helpful than gathering all the results.

I agree to report per-table information. Especially In case of one of
tables specified failed during vacuuming, I think we should report at
least information of tables that is done successfully so far.

>
>>> I’ve attached my first attempt at introducing this functionality.  In the patch, I’ve extended the table_name
parameterin the VACUUM grammar to a qualified_name_list.  While this fits into the grammar decently well, I suspect
thatit may be desirable to be able to specify a column list for each table as well (e.g. VACUUM foo (a), bar (b)). 
>>
>> The column list only matters for ANALYZE (or VACUUM ANALYZE).  But yes,
>> it should be per-table.
>
> The grammar allows that by the way:
> =# VACUUM (full) aa (a);
> VACUUM
> Perhaps that's an oversight? I don't think it makes much sense.
> --
> Michael
>
>
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Regards,

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