Subject: Re: Creating a function for exposing memory usage of backend process
From: Fujii Masao <masao.fujii@oss.nttdata.com>
To: torikoshia <torikoshia@oss.nttdata.com>
Cc: Michael Paquier <michael@paquier.xyz>,
 Kasahara Tatsuhito <kasahara.tatsuhito@gmail.com>,
 Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>,
 Robert Haas <robertmhaas@gmail.com>
References: <261eebda3e1909475162b968e5a4ad2b@oss.nttdata.com>
 <66ae5b88-208d-96fa-c20a-fb539b597859@oss.nttdata.com>
 <20200819135545.GC19121@paquier.xyz> <1414992.1597849297@sss.pgh.pa.us>
 <20200819225343.c7rxteydi35nhrdp@alap3.anarazel.de>
 <1554676.1597886946@sss.pgh.pa.us>
 <20200820014301.5pr7qjugnvpovu62@alap3.anarazel.de>
 <d97ad430-444d-9ec8-21dd-a1584569309b@oss.nttdata.com>
 <CAP0=ZVJ5VZsUYLFkc-E5_JHTc1ZdemX28VgQqUXJLTywC=9hfA@mail.gmail.com>
 <a8f3c385e9edeba4833c712270d6e6d9@oss.nttdata.com>
 <20200822121641.GE2108@paquier.xyz>
 <c9515ae497b4a077360a31547782acb8@oss.nttdata.com>
 <07da4267-74bf-4a6b-3312-4ab7c1e72f66@oss.nttdata.com>
 <ae118b75ede9327c6dc8e9e457639dc9@oss.nttdata.com>
 <2cfafd6e-8b4e-7b5c-3dca-ca474662d5ca@oss.nttdata.com>
Message-ID: <50d00902-7638-ea22-7fa4-0c7c377aa085@oss.nttdata.com>
Date: Wed, 26 Aug 2020 10:54:19 +0900
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On 2020/08/25 11:39, Fujii Masao wrote:
> 
> 
> On 2020/08/24 21:56, torikoshia wrote:
>> On 2020-08-24 13:13, Fujii Masao wrote:
>>> On 2020/08/24 13:01, torikoshia wrote:
>>>> On 2020-08-22 21:18, Michael Paquier wrote:
>>>>
>>>> Thanks for reviewing!
>>>>
>>>>> On Fri, Aug 21, 2020 at 11:27:06PM +0900, torikoshia wrote:
>>>>>> OK. Added a regression test on sysviews.sql.
>>>>>> (0001-Added-a-regression-test-for-pg_backend_memory_contex.patch)
>>>>>>
>>>>>> Fujii-san gave us an example, but I added more simple one considering
>>>>>> the simplicity of other tests on that.
>>>>>
>>>>> What you have sent in 0001 looks fine to me.  A small test is much
>>>>> better than nothing.
>>>
>>> +1
>>>
>>> But as I proposed upthread, what about a bit complicated test as follows,
>>> e.g., to confirm that the internal logic for level works expectedly?
>>>
>>>      SELECT name, ident, parent, level, total_bytes >= free_bytes FROM
>>> pg_backend_memory_contexts WHERE level = 0;
>>
>> OK!
>> Attached an updated patch.
> 
> Thanks for updating the patch! Looks good to me.
> Barring any objection, I will commit this patch.
> 
>>
>>>
>>>
>>>>>
>>>>>> Added a patch for relocating the codes to mcxtfuncs.c.
>>>>>> (patches/0001-Rellocated-the-codes-for-pg_backend_memory_contexts-.patch)
>>>
>>> Thanks for the patch! Looks good to me.
>>> Barring any objection, I will commit this patch at first.
>>>
>>>
>>>>>
>>>>> The same code is moved around line-by-line.
>>>>>
>>>>>> Of course, this restriction makes pg_backend_memory_contexts hard to use
>>>>>> when the user of the target session is not granted pg_monitor because the
>>>>>> scope of this view is session local.
>>>>>>
>>>>>> In this case, I imagine additional operations something like temporarily
>>>>>> granting pg_monitor to that user.
>>>>>
>>>>> Hmm.  I am not completely sure either that pg_monitor is the best fit
>>>>> here, because this view provides information about a bunch of internal
>>>>> structures.  Something that could easily be done though is to revoke
>>>>> the access from public, and then users could just set up GRANT
>>>>> permissions post-initdb, with pg_monitor as one possible choice. This
>>>>> is the safest path by default, and this stuff is of a caliber similar
>>>>> to pg_shmem_allocations in terms of internal contents.
>>>>
>>>> I think this is a better way than what I did in
>>>> 0001-Rellocated-the-codes-for-pg_backend_memory_contexts-.patch.
>>>
>>> You mean 0001-Restrict-the-access-to-pg_backend_memory_contexts-to.patch?
>>
>> Oops, I meant 0001-Restrict-the-access-to-pg_backend_memory_contexts-to.patch.
> 
> This patch also looks good to me. Thanks!

I pushed the proposed three patches. Thanks!

Regards,

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