Re: ANALYZE ONLY - Mailing list pgsql-hackers

On 2024-09-01 10:31, Michael Harris wrote:
> Hello Atsushi & Melih
> 
> Thank you both for your further feedback.
> 
> On Thu, 29 Aug 2024 at 21:31, Melih Mutlu <m.melihmutlu@gmail.com> 
> wrote:
>> I believe moving "[ ONLY ]" to the definitions of table_and_columns 
>> below, as you did with "[ * ]", might be better to be consistent with 
>> other places (see [1])
> 
> Agreed. I have updated this.
> 
>>> + if ((options & VACOPT_VACUUM) && is_partitioned_table && ! 
>>> include_children)
>> 
>> There are also some issues with coding conventions in some places 
>> (e.g. the space between "!" and "include_children" abode). I think 
>> running pgindent would resolve such issue in most places.
> 
> I fixed that extra space, and then ran pgindent. It did not report any
> more problems.
> 
> On Fri, 30 Aug 2024 at 16:45, torikoshia <torikoshia@oss.nttdata.com> 
> wrote:
>> -- https://www.postgresql.org/docs/devel/progress-reporting.html
>> > Note that when ANALYZE is run on a partitioned table, all of its
>> > partitions are also recursively analyzed.
>> 
>> Should we also note this is the default, i.e. not using ONLY option
>> behavior here?
> 
>> -- https://www.postgresql.org/docs/devel/ddl-partitioning.html
>> > If you are using manual VACUUM or ANALYZE commands, don't forget that
>> > you need to run them on each child table individually. A command like:
>> >
>> > ANALYZE measurement;
>> > will only process the root table.
>> 
>> This part also should be modified, shouldn't it?
> 
> Agreed. I have updated both of these.

Thanks!

>> When running ANALYZE VERBOSE ONLY on a partition table, the INFO 
>> message
>> is like this:
>> 
>>    =# ANALYZE VERBOSE ONLY only_parted;
>>    INFO:  analyzing "public.only_parted" inheritance tree
>> 
>> I may be wrong, but 'inheritance tree' makes me feel it includes child
>> tables.
>> Removing 'inheritance tree' and just describing the table name as 
>> below
>> might be better:
>> 
>>    INFO:  analyzing "public.only_parted"
> 
> I'm not sure about that one. If I understand the source correctly,
> that particular progress
> message tells the user that the system is gathering stats from the 
> inheritance
> tree in order to update the stats of the given table, not that it is
> actually updating
> the stats of the descendant tables.

That makes sense.

> When analyzing an inheritance structure with the ONLY you see
> something like this:
> 
> => ANALYZE VERBOSE ONLY only_inh_parent;
> INFO:  analyzing "public.only_inh_parent"
> INFO:  "only_inh_parent": scanned 0 of 0 pages, containing 0 live rows
> and 0 dead rows; 0 rows in sample, 0 estimated total rows
> INFO:  analyzing "public.only_inh_parent" inheritance tree
> INFO:  "only_inh_child": scanned 1 of 1 pages, containing 3 live rows
> and 0 dead rows; 3 rows in sample, 3 estimated total rows
> ANALYZE
> 
> The reason you don't see the first one for partitioned tables is that
> it corresponds
> to sampling the contents of the parent table itself, which in the case
> of a partitioned
> table is guaranteed to be empty, so it is skipped.
> 
> I agree the text could be confusing, and in fact is probably confusing
> even today
> without the ONLY keyword,

Yeah, it seems this isn't dependent on your proposal.
(BTW I'm also wondering if the expression “inheritance" is appropriate 
when the target is a partitioned table, but this should be discussed in 
another thread)


-- 
Regards,

--
Atsushi Torikoshi
NTT DATA Group Corporation