Fix search_path to a safe value during maintenance operations.

While executing maintenance operations (ANALYZE, CLUSTER, REFRESH
MATERIALIZED VIEW, REINDEX, or VACUUM), set search_path to
'pg_catalog, pg_temp' to prevent inconsistent behavior.

Functions that are used for functional indexes, in index expressions,
or in materialized views and depend on a different search path must be
declared with CREATE FUNCTION ... SET search_path='...'.

This change was previously committed as 05e1737, then reverted in
commit 2fcc7ee because it was too late in the cycle.

Preparation for the MAINTAIN privilege, which was previously reverted
due to search_path manipulation hazards.

Discussion: https://postgr.es/m/d4ccaf3658cb3c281ec88c851a09733cd9482f22.camel@j-davis.com
Discussion: https://postgr.es/m/E1q7j7Y-000z1H-Hr%40gemulon.postgresql.org
Discussion: https://postgr.es/m/e44327179e5c9015c8dda67351c04da552066017.camel%40j-davis.com
Reviewed-by: Greg Stark, Nathan Bossart, Noah Misch

Author: jeff-davis

contrib/amcheck/t/004_verify_nbtree_unique.pl

@@ -20,8 +20,11 @@
 	'postgres', q(
 	CREATE EXTENSION amcheck;
 
+	CREATE SCHEMA test_amcheck;
+	SET search_path = test_amcheck;
+
 	CREATE FUNCTION ok_cmp (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT
 			CASE WHEN $1 < $2 THEN -1
@@ -34,7 +37,7 @@
 	--- Check 1: uniqueness violation.
 	---
 	CREATE FUNCTION ok_cmp1 (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT ok_cmp($1, $2);
 	$$;
@@ -43,7 +46,7 @@
 	--- Make values 768 and 769 look equal.
 	---
 	CREATE FUNCTION bad_cmp1 (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT
 			CASE WHEN ($1 = 768 AND $2 = 769) OR
@@ -56,13 +59,13 @@
 	--- Check 2: uniqueness violation without deduplication.
 	---
 	CREATE FUNCTION ok_cmp2 (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT ok_cmp($1, $2);
 	$$;
 
 	CREATE FUNCTION bad_cmp2 (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT
 			CASE WHEN $1 = $2 AND $1 = 400 THEN -1
@@ -74,13 +77,13 @@
 	--- Check 3: uniqueness violation with deduplication.
 	---
 	CREATE FUNCTION ok_cmp3 (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT ok_cmp($1, $2);
 	$$;
 
 	CREATE FUNCTION bad_cmp3 (int4, int4)
-	RETURNS int LANGUAGE sql AS
+	RETURNS int LANGUAGE sql SET search_path = test_amcheck AS
 	$$
 		SELECT bad_cmp2($1, $2);
 	$$;
@@ -142,22 +145,23 @@
 # We have not yet broken the index, so we should get no corruption
 $result = $node->safe_psql(
 	'postgres', q(
-	SELECT bt_index_check('bttest_unique_idx1', true, true);
+	SELECT bt_index_check('test_amcheck.bttest_unique_idx1', true, true);
 ));
 is($result, '', 'run amcheck on non-broken bttest_unique_idx1');
 
 # Change the operator class to use a function which considers certain different
 # values to be equal.
 $node->safe_psql(
 	'postgres', q(
+	SET search_path = test_amcheck;
 	UPDATE pg_catalog.pg_amproc SET
 		   amproc = 'bad_cmp1'::regproc
 	WHERE amproc = 'ok_cmp1'::regproc;
 ));
 
 ($result, $stdout, $stderr) = $node->psql(
 	'postgres', q(
-	SELECT bt_index_check('bttest_unique_idx1', true, true);
+	SELECT bt_index_check('test_amcheck.bttest_unique_idx1', true, true);
 ));
 ok( $stderr =~ /index uniqueness is violated for index "bttest_unique_idx1"/,
 	'detected uniqueness violation for index "bttest_unique_idx1"');
@@ -175,21 +179,22 @@
 # but no uniqueness violation.
 ($result, $stdout, $stderr) = $node->psql(
 	'postgres', q(
-	SELECT bt_index_check('bttest_unique_idx2', true, true);
+	SELECT bt_index_check('test_amcheck.bttest_unique_idx2', true, true);
 ));
 ok( $stderr =~ /item order invariant violated for index "bttest_unique_idx2"/,
 	'detected item order invariant violation for index "bttest_unique_idx2"');
 
 $node->safe_psql(
 	'postgres', q(
+	SET search_path = test_amcheck;
 	UPDATE pg_catalog.pg_amproc SET
 		   amproc = 'ok_cmp2'::regproc
 	WHERE amproc = 'bad_cmp2'::regproc;
 ));
 
 ($result, $stdout, $stderr) = $node->psql(
 	'postgres', q(
-	SELECT bt_index_check('bttest_unique_idx2', true, true);
+	SELECT bt_index_check('test_amcheck.bttest_unique_idx2', true, true);
 ));
 ok( $stderr =~ /index uniqueness is violated for index "bttest_unique_idx2"/,
 	'detected uniqueness violation for index "bttest_unique_idx2"');
@@ -206,7 +211,7 @@
 # but no uniqueness violation.
 ($result, $stdout, $stderr) = $node->psql(
 	'postgres', q(
-	SELECT bt_index_check('bttest_unique_idx3', true, true);
+	SELECT bt_index_check('test_amcheck.bttest_unique_idx3', true, true);
 ));
 ok( $stderr =~ /item order invariant violated for index "bttest_unique_idx3"/,
 	'detected item order invariant violation for index "bttest_unique_idx3"');
@@ -215,6 +220,7 @@
 # with different visibility.
 $node->safe_psql(
 	'postgres', q(
+	SET search_path = test_amcheck;
 	DELETE FROM bttest_unique3 WHERE 380 <= i AND i <= 420;
 	INSERT INTO bttest_unique3 (SELECT * FROM generate_series(380, 420));
 	INSERT INTO bttest_unique3 VALUES (400);
@@ -228,14 +234,15 @@
 
 $node->safe_psql(
 	'postgres', q(
+	SET search_path = test_amcheck;
 	UPDATE pg_catalog.pg_amproc SET
 		   amproc = 'ok_cmp3'::regproc
 	WHERE amproc = 'bad_cmp3'::regproc;
 ));
 
 ($result, $stdout, $stderr) = $node->psql(
 	'postgres', q(
-	SELECT bt_index_check('bttest_unique_idx3', true, true);
+	SELECT bt_index_check('test_amcheck.bttest_unique_idx3', true, true);
 ));
 ok( $stderr =~ /index uniqueness is violated for index "bttest_unique_idx3"/,
 	'detected uniqueness violation for index "bttest_unique_idx3"');

contrib/amcheck/verify_nbtree.c

@@ -313,6 +313,8 @@ bt_index_check_internal(Oid indrelid, bool parentcheck, bool heapallindexed,
 		SetUserIdAndSecContext(heaprel->rd_rel->relowner,
 							   save_sec_context | SECURITY_RESTRICTED_OPERATION);
 		save_nestlevel = NewGUCNestLevel();
+		SetConfigOption("search_path", GUC_SAFE_SEARCH_PATH, PGC_USERSET,
+						PGC_S_SESSION);
 	}
 	else
 	{

doc/src/sgml/amcheck.sgml

@@ -24,6 +24,9 @@
   to hold, we can expect binary searches on the affected page to
   incorrectly guide index scans, resulting in wrong answers to SQL
   queries.  If the structure appears to be valid, no error is raised.
+  While these checking functions are run, the <xref
+  linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+  pg_temp</literal>.
  </para>
  <para>
   Verification is performed using the same procedures as those used by

doc/src/sgml/brin.sgml

@@ -95,7 +95,9 @@
   </para>
 
   <para>
-   Lastly, the following functions can be used:
+   Lastly, the following functions can be used (while these functions run,
+   <xref linkend="guc-search-path"/> is temporarily changed to
+   <literal>pg_catalog, pg_temp</literal>):
    <simplelist>
     <member>
      <function>brin_summarize_new_values(regclass)</function>

doc/src/sgml/ref/analyze.sgml

@@ -205,6 +205,12 @@ ANALYZE [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <r
    (This will not be sufficient if there is heavy update activity.)
   </para>
 
+  <para>
+   While <command>ANALYZE</command> is running, the <xref
+   linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+   pg_temp</literal>.
+  </para>
+
   <para>
    <command>ANALYZE</command>
    requires only a read lock on the target table, so it can run in

doc/src/sgml/ref/cluster.sgml

@@ -153,6 +153,12 @@ CLUSTER [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <r
     information.
    </para>
 
+   <para>
+    While <command>CLUSTER</command> is running, the <xref
+    linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+    pg_temp</literal>.
+   </para>
+
    <para>
     When an index scan is used, a temporary copy of the table is created that
     contains the table data in the index order.  Temporary copies of each

doc/src/sgml/ref/create_index.sgml

@@ -789,6 +789,12 @@ Indexes:
    the table to generate statistics for these indexes.
   </para>
 
+  <para>
+   While <command>CREATE INDEX</command> is running, the <xref
+   linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+   pg_temp</literal>.
+  </para>
+
   <para>
    For most index methods, the speed of creating an index is
    dependent on the setting of <xref linkend="guc-maintenance-work-mem"/>.

doc/src/sgml/ref/refresh_materialized_view.sgml

@@ -98,6 +98,12 @@ REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] <replaceable class="parameter">name</
    will be ordered that way; but <command>REFRESH MATERIALIZED
    VIEW</command> does not guarantee to preserve that ordering.
   </para>
+
+  <para>
+   While <command>REFRESH MATERIALIZED VIEW</command> is running, the <xref
+   linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+   pg_temp</literal>.
+  </para>
  </refsect1>
 
  <refsect1>

doc/src/sgml/ref/reindex.sgml

@@ -291,6 +291,12 @@ REINDEX [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] { DA
    into expensive sequential scans.
   </para>
 
+  <para>
+   While <command>REINDEX</command> is running, the <xref
+   linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+   pg_temp</literal>.
+  </para>
+
   <para>
    Reindexing a single index or table requires being the owner of that
    index or table.  Reindexing a schema or database requires being the

doc/src/sgml/ref/vacuum.sgml

@@ -443,6 +443,12 @@ VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <re
     does not have permission to vacuum.
    </para>
 
+   <para>
+    While <command>VACUUM</command> is running, the <xref
+    linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+    pg_temp</literal>.
+   </para>
+
    <para>
     <command>VACUUM</command> cannot be executed inside a transaction block.
    </para>