Date: Tue, 30 Jul 2024 01:36:55 +0200
From: Erik Wienhold <ewie@ewie.name>
To: Yugo NAGATA <nagata@sraoss.co.jp>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: psql: Add leakproof field to \dAo+ meta-command results
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On 2024-07-01 15:08 +0200, Yugo NAGATA wrote:
> I would like to propose to add a new field to psql's \dAo+ meta-command
> to show whether the underlying function of an operator is leak-proof.

+1 for making that info easily accessible.

> This idea is inspired from [1] that claims some indexes uses non-LEAKPROOF
> functions under the associated operators, as a result, it can not be selected
> for queries with security_barrier views or row-level security policies.
> The original proposal was to add a query over system catalogs for looking up
> non-leakproof operators to the documentation, but I thought it is useful
> to improve \dAo results rather than putting such query to the doc.
> 
> The attached patch adds the field to \dAo+ and also a description that
> explains the relation between indexes and security quals with referencing
> \dAo+ meta-command.
> 
> [1] https://www.postgresql.org/message-id/raw/5af3bf0c-5e0c-4128-81dc-084c5258b1af%40code406.com

\dAo+ output looks good.

But this patch fails regression tests in src/test/regress/sql/psql.sql
(\dAo+ btree float_ops) because of the new leak-proof column.  I think
this could even be changed to "\dAo+ btree array_ops|float_ops" to also
cover operators that are not leak-proof.

+<para>
+    For example, an index scan can not be selected for queries with

I check the docs and "cannot" is more commonly used than "can not".

+    <literal>security_barrier</literal> views or row-level security policies if an
+    operator used in the <literal>WHERE</literal> clause is associated with the
+    operator family of the index, but its underlying function is not marked
+    <literal>LEAKPROOF</literal>. The <xref linkend="app-psql"/> program's
+    <command>\dAo+</command> meta-command is useful for listing the operators
+    with associated operator families and whether it is leak-proof.
+</para>

I think the last sentence can be improved.  How about: "Use psql's \dAo+
command to list operator families and tell which of their operators are
marked as leak-proof."?  Should something similar be added to [1] which
also talks about leak-proof operators?

The rest is just formatting nitpicks:

+                         ", ofs.opfname AS \"%s\"\n,"

The trailing comma should come before the newline.

+                         "  CASE\n"
+                         "   WHEN p.proleakproof THEN '%s'\n"
+                         "   ELSE '%s'\n"
+                         " END AS \"%s\"\n",

WHEN/ELSE/END should be intended with one additional space to be
consistent with the other CASE expressions in this query.

[1] https://www.postgresql.org/docs/devel/planner-stats-security.html

-- 
Erik