From 43661926deb7d412ae3a22a43dadb9def7b7e46c Mon Sep 17 00:00:00 2001
From: Noah Misch <noah@leadboat.com>
Date: Tue, 26 Sep 2017 22:39:44 -0700
Subject: [PATCH] Don't recommend "DROP SCHEMA information_schema CASCADE".

It drops objects outside information_schema that depend on objects
inside information_schema.  For example, it will drop a user-defined
view if the view query refers to information_schema.

Discussion: https://postgr.es/m/20170831025345.GE3963697@rfd.leadboat.com
---
 doc/src/sgml/release-9.2.sgml | 44 +++++++++++++++++++++++++++++------
 doc/src/sgml/release-9.3.sgml | 44 +++++++++++++++++++++++++++++------
 2 files changed, 74 insertions(+), 14 deletions(-)

diff --git a/doc/src/sgml/release-9.2.sgml b/doc/src/sgml/release-9.2.sgml
index 81186495543..8077b863d69 100644
--- a/doc/src/sgml/release-9.2.sgml
+++ b/doc/src/sgml/release-9.2.sgml
@@ -58,14 +58,44 @@
       in an existing installation, you can, as a superuser, do this
       in <application>psql</>:
 <programlisting>
-BEGIN;
-DROP SCHEMA information_schema CASCADE;
-\i <replaceable>SHAREDIR</>/information_schema.sql
-COMMIT;
+SET search_path TO information_schema;
+CREATE OR REPLACE VIEW table_privileges AS
+    SELECT CAST(u_grantor.rolname AS sql_identifier) AS grantor,
+           CAST(grantee.rolname AS sql_identifier) AS grantee,
+           CAST(current_database() AS sql_identifier) AS table_catalog,
+           CAST(nc.nspname AS sql_identifier) AS table_schema,
+           CAST(c.relname AS sql_identifier) AS table_name,
+           CAST(c.prtype AS character_data) AS privilege_type,
+           CAST(
+             CASE WHEN
+                  -- object owner always has grant options
+                  pg_has_role(grantee.oid, c.relowner, 'USAGE')
+                  OR c.grantable
+                  THEN 'YES' ELSE 'NO' END AS yes_or_no) AS is_grantable,
+           CAST(CASE WHEN c.prtype = 'SELECT' THEN 'YES' ELSE 'NO' END AS yes_or_no) AS with_hierarchy
+
+    FROM (
+            SELECT oid, relname, relnamespace, relkind, relowner, (aclexplode(coalesce(relacl, acldefault('r', relowner)))).* FROM pg_class
+         ) AS c (oid, relname, relnamespace, relkind, relowner, grantor, grantee, prtype, grantable),
+         pg_namespace nc,
+         pg_authid u_grantor,
+         (
+           SELECT oid, rolname FROM pg_authid
+           UNION ALL
+           SELECT 0::oid, 'PUBLIC'
+         ) AS grantee (oid, rolname)
+
+    WHERE c.relnamespace = nc.oid
+          AND c.relkind IN ('r', 'v', 'f')
+          AND c.grantee = grantee.oid
+          AND c.grantor = u_grantor.oid
+          AND c.prtype IN ('INSERT', 'SELECT', 'UPDATE', 'DELETE', 'TRUNCATE', 'REFERENCES', 'TRIGGER')
+          AND (pg_has_role(u_grantor.oid, 'USAGE')
+               OR pg_has_role(grantee.oid, 'USAGE')
+               OR grantee.rolname = 'PUBLIC');
 </programlisting>
-      (Run <literal>pg_config --sharedir</> if you're uncertain
-      where <replaceable>SHAREDIR</> is.)  This must be repeated in each
-      database to be fixed.
+      This must be repeated in each database to be fixed,
+      including <literal>template0</>.
      </para>
     </listitem>
 
diff --git a/doc/src/sgml/release-9.3.sgml b/doc/src/sgml/release-9.3.sgml
index 9eaf5d54db8..d11a302d07e 100644
--- a/doc/src/sgml/release-9.3.sgml
+++ b/doc/src/sgml/release-9.3.sgml
@@ -52,14 +52,44 @@
       in an existing installation, you can, as a superuser, do this
       in <application>psql</>:
 <programlisting>
-BEGIN;
-DROP SCHEMA information_schema CASCADE;
-\i <replaceable>SHAREDIR</>/information_schema.sql
-COMMIT;
+SET search_path TO information_schema;
+CREATE OR REPLACE VIEW table_privileges AS
+    SELECT CAST(u_grantor.rolname AS sql_identifier) AS grantor,
+           CAST(grantee.rolname AS sql_identifier) AS grantee,
+           CAST(current_database() AS sql_identifier) AS table_catalog,
+           CAST(nc.nspname AS sql_identifier) AS table_schema,
+           CAST(c.relname AS sql_identifier) AS table_name,
+           CAST(c.prtype AS character_data) AS privilege_type,
+           CAST(
+             CASE WHEN
+                  -- object owner always has grant options
+                  pg_has_role(grantee.oid, c.relowner, 'USAGE')
+                  OR c.grantable
+                  THEN 'YES' ELSE 'NO' END AS yes_or_no) AS is_grantable,
+           CAST(CASE WHEN c.prtype = 'SELECT' THEN 'YES' ELSE 'NO' END AS yes_or_no) AS with_hierarchy
+
+    FROM (
+            SELECT oid, relname, relnamespace, relkind, relowner, (aclexplode(coalesce(relacl, acldefault('r', relowner)))).* FROM pg_class
+         ) AS c (oid, relname, relnamespace, relkind, relowner, grantor, grantee, prtype, grantable),
+         pg_namespace nc,
+         pg_authid u_grantor,
+         (
+           SELECT oid, rolname FROM pg_authid
+           UNION ALL
+           SELECT 0::oid, 'PUBLIC'
+         ) AS grantee (oid, rolname)
+
+    WHERE c.relnamespace = nc.oid
+          AND c.relkind IN ('r', 'v', 'f')
+          AND c.grantee = grantee.oid
+          AND c.grantor = u_grantor.oid
+          AND c.prtype IN ('INSERT', 'SELECT', 'UPDATE', 'DELETE', 'TRUNCATE', 'REFERENCES', 'TRIGGER')
+          AND (pg_has_role(u_grantor.oid, 'USAGE')
+               OR pg_has_role(grantee.oid, 'USAGE')
+               OR grantee.rolname = 'PUBLIC');
 </programlisting>
-      (Run <literal>pg_config --sharedir</> if you're uncertain
-      where <replaceable>SHAREDIR</> is.)  This must be repeated in each
-      database to be fixed.
+      This must be repeated in each database to be fixed,
+      including <literal>template0</>.
      </para>
     </listitem>