Re: [doc] plan invalidation when statistics are update

On 2020/11/19 14:33, torikoshia wrote:
> On 2020-11-18 11:35, Fujii Masao wrote:
> 
> Thanks for your comment!
> 
>> On 2020/11/18 11:04, torikoshia wrote:
>>> Hi,
>>>
>>> AFAIU, when the planner statistics are updated, generic plans are invalidated and PostgreSQL recreates. However,
themanual doesn't seem to explain it explicitly.
 
>>>
>>>    https://www.postgresql.org/docs/devel/sql-prepare.html
>>>
>>> I guess this case is included in 'whenever database objects used in the statement have definitional (DDL) changes
undergone',but I feel it's hard to infer.
 
>>>
>>> Since updates of the statistics can often happen, how about describing this case explicitly like an attached
patch?
>>
>> +1 to add that note.
>>
>> -   statement.  Also, if the value of <xref linkend="guc-search-path"/> changes
>> +   statement. For example, when the planner statistics of the statement
>> +   are updated, <productname>PostgreSQL</productname> re-analyzes and
>> +   re-plans the statement.
>>
>> I don't think "For example," is necessary.
>>
>> "planner statistics of the statement" sounds vague? Does the statement
>> is re-analyzed and re-planned only when the planner statistics of database
>> objects used in the statement are updated? If yes, we should describe
>> that to make the note a bit more explicitly?
> 
> Yes. As far as I confirmed, updating statistics which are not used in
> prepared statements doesn't trigger re-analyze and re-plan.
> 
> Since plan invalidations for DDL changes and statistcal changes are caused
> by PlanCacheRelCallback(Oid 'relid'), only the prepared statements using
> 'relid' relation seem invalidated.> 
> Attached updated patch.

Thanks for confirming that and updating the patch!
Barring any objection, I will commit the patch.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION