Message-ID: <52784DF9.9040205@2ndquadrant.com>
Date: Tue, 05 Nov 2013 09:46:33 +0800
From: Craig Ringer <craig@2ndquadrant.com>
Organization: 2nd Quadrant
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To: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
CC: Stephen Frost <sfrost@snowman.net>, Josh Berkus <josh@agliodbs.com>,
 Kohei KaiGai <kaigai@kaigai.gr.jp>, "ktm@rice.edu" <ktm@rice.edu>,
 Alexander Korotkov <aekorotkov@gmail.com>,
 Oleg Bartunov <obartunov@gmail.com>, Greg Smith <greg@2ndquadrant.com>,
 PgHacker <pgsql-hackers@postgresql.org>
Subject: Re: [v9.4] row level security
References: 
 <CADyhKSWkHrPqbRsFK0LjPMOOTsbKGWOuN75GqYJrxCDO3CKWtA@mail.gmail.com>
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	<WM!685df689dd4d8f8c5349d5ef7b8e285db1e99ea32d22ab5d35f3981c29eac19dbd725c9b5e0227def9d782de274d1354!@asav-3.01.com>
	<521F7DFB.8060602@agliodbs.com>
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	<5220D832.7090104@agliodbs.com>	<20130830192729.GO2706@tamriel.snowman.net>
	<16798.1377891794@sss.pgh.pa.us>
	<CA+TgmoZYv_me1iB6iDRA_oO-o9xkxXYqr-0UtwK5itpZbDsqYA@mail.gmail.com>
	<1398.1378305956@sss.pgh.pa.us>
	<CA+TgmoYTf+4RUOW8stVz1RE+3TD+QR5TNKzYuFDCehSkieL5OQ@mail.gmail.com>
	<1543.1378306249@sss.pgh.pa.us>	<2620.1378308159@sss.pgh.pa.us>
	<52775604.9090306@2ndquadrant.com>	<11101.1383575839@sss.pgh.pa.us>
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On 11/04/2013 11:17 PM, Robert Haas wrote:
> I'd still like to here what's wrong with what I said here:
> 
> http://www.postgresql.org/message-id/CA+TgmoYr1PHw3X9vnVuWDcfXkzK2p_jhtWc0fV2Q58NEgcxyTA@mail.gmail.com

For me, just my understanding. I'm still too new to the planner and
rewriter to grasp that properly as written.

I was responding to Tom's objection, and he makes a good point about
CASE and optimisation. We have to be free to re-order and pre-evaluate
where LEAKPROOF flags make it safe and permissible, without ever
otherwise doing so. That makes the SECURITY BARRIER subquery look
better, since the limited pull-up / push-down is already implemented there.

Robert, any suggesitons on how to approach what you suggest? I'm pretty
new to the planner's guts, but I know there've been some complaints
about the way the current RLS code fiddles with Vars when it changes a
direct scan of a rel into a subquery scan.

The code in:

https://github.com/ringerc/postgres/blob/rls-9.4/src/backend/optimizer/prep/prepunion.c#L1647

and

https://github.com/ringerc/postgres/blob/rls-9.4/src/backend/optimizer/prep/prepunion.c#L1591

seems to be the one folks were complaining about earlier.


-- 
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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