Subject: Re: table partitioning and access privileges
To: Amit Langote <amitlangote09@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Fujii Masao <masao.fujii@gmail.com>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
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From: Fujii Masao <masao.fujii@oss.nttdata.com>
Message-ID: <f3dba4e6-ddeb-5126-b9a6-13a04c7c23dc@oss.nttdata.com>
Date: Fri, 31 Jan 2020 21:39:01 +0900
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On 2020/01/31 13:38, Amit Langote wrote:
> On Fri, Jan 31, 2020 at 1:28 AM Fujii Masao <masao.fujii@oss.nttdata.com> wrote:
>> On 2020/01/31 1:02, Tom Lane wrote:
>>> Fujii Masao <masao.fujii@oss.nttdata.com> writes:
>>>> Thanks for updating the patch! Barring any objection,
>>>> I will commit this fix and backport it to all supported versions.
>>>
>>> Sorry for not having paid closer attention to this thread, but ...
>>> is back-patching this behavioral change really a good idea?
>>>
>>> It's not that hard to imagine that somebody is expecting the old
>>> behavior and will complain that we broke their application's security.
>>> So I'd have thought it better to fix only in HEAD, with a
>>> compatibility warning in the v13 release notes.
>>>
>>> I'm afraid it's much more likely that people will complain about
>>> making such a change in a minor release than that they will be
>>> happy about it.  It's particularly risky to be making it in what
>>> will be the last 9.4.x release, because we will not have any
>>> opportunity to undo it in that branch if there is pushback.
>>
>> Fair enough. I finally did back-patch because the behavior is clearly
>> documented and I failed to hear the opinions to object the back-patch.
>> But I should have heard and discussed such risks more.
>>
>> I'm OK to revert all those back-patch. Instead, probably the document
>> should be updated in old branches.
> 
> I could find only this paragraph in the section on inheritance that
> talks about how access permissions work:
> 
> 9.4:
> 
> "Note how table access permissions are handled. Querying a parent
> table can automatically access data in child tables without further
> access privilege checking. This preserves the appearance that the data
> is (also) in the parent table. Accessing the child tables directly is,
> however, not automatically allowed and would require further
> privileges to be granted."
> 
> 9.5-12:
> 
> "Inherited queries perform access permission checks on the parent
> table only. Thus, for example, granting UPDATE permission on the
> cities table implies permission to update rows in the capitals table
> as well, when they are accessed through cities. This preserves the
> appearance that the data is (also) in the parent table. But the
> capitals table could not be updated directly without an additional
> grant. In a similar way, the parent table's row security policies (see
> Section 5.7) are applied to rows coming from child tables during an
> inherited query. A child table's policies, if any, are applied only
> when it is the table explicitly named in the query; and in that case,
> any policies attached to its parent(s) are ignored."
> 
> Do you mean that the TRUNCATE exception should be noted here?

Yes, that's what I was thinking.

Regards,

-- 
Fujii Masao
NTT DATA CORPORATION
Advanced Platform Technology Group
Research and Development Headquarters