Add test for session_preload_libraries and parameter permissions checks.

We weren't exercising the session_preload_libraries option in any
meaningful way.  auto_explain is a good testbed for doing so, since
it's one of the primary use-cases for session_preload_libraries.
Hence, adjust its TAP test to load the library via
session_preload_libraries not shared_preload_libraries.  While at it,
feed test-specific settings to the backend via PGOPTIONS rather than
tediously rewriting postgresql.conf.

Also, since auto_explain has some PGC_SUSET parameters, we can use it
to provide a test case for the permissions-checking bug just fixed
by commit b35617d.

Back-patch to v15 so that we have coverage for the permissions issue
in that branch too.  To do that, I back-patched the refactoring
recently done by commit 550bc0a.

Dagfinn Ilmari Mannsåker and Tom Lane

Discussion: https://postgr.es/m/CABwTF4VEpwTHhRQ+q5MiC5ucngN-whN-PdcKeufX7eLSoAfbZA@mail.gmail.com

Author: tglsfdc

contrib/auto_explain/t/001_auto_explain.pl

@@ -9,45 +9,28 @@
 use Test::More;
 
 # Runs the specified query and returns the emitted server log.
-# If any parameters are specified, these are set in postgresql.conf,
-# and reset after the query is run.
+# params is an optional hash mapping GUC names to values;
+# any such settings are transmitted to the backend via PGOPTIONS.
 sub query_log
 {
 	my ($node, $sql, $params) = @_;
 	$params ||= {};
 
-	if (keys %$params)
-	{
-		for my $key (keys %$params)
-		{
-			$node->append_conf('postgresql.conf', "$key = $params->{$key}\n");
-		}
-		$node->reload;
-	}
+	local $ENV{PGOPTIONS} = join " ",
+	  map { "-c $_=$params->{$_}" } keys %$params;
 
 	my $log    = $node->logfile();
 	my $offset = -s $log;
 
 	$node->safe_psql("postgres", $sql);
 
-	my $log_contents = slurp_file($log, $offset);
-
-	if (keys %$params)
-	{
-		for my $key (keys %$params)
-		{
-			$node->adjust_conf('postgresql.conf', $key, undef);
-		}
-		$node->reload;
-	}
-
-	return $log_contents;
+	return slurp_file($log, $offset);
 }
 
 my $node = PostgreSQL::Test::Cluster->new('main');
 $node->init;
 $node->append_conf('postgresql.conf',
-	"shared_preload_libraries = 'auto_explain'");
+	"session_preload_libraries = 'auto_explain'");
 $node->append_conf('postgresql.conf', "auto_explain.log_min_duration = 0");
 $node->append_conf('postgresql.conf', "auto_explain.log_analyze = on");
 $node->start;
@@ -126,12 +109,12 @@ sub query_log
 # JSON format.
 $log_contents = query_log(
 	$node,
-	"SELECT * FROM pg_proc;",
+	"SELECT * FROM pg_class;",
 	{ "auto_explain.log_format" => "json" });
 
 like(
 	$log_contents,
-	qr/"Query Text": "SELECT \* FROM pg_proc;"/,
+	qr/"Query Text": "SELECT \* FROM pg_class;"/,
 	"query text logged, json mode");
 
 unlike(
@@ -141,7 +124,7 @@ sub query_log
 
 like(
 	$log_contents,
-	qr/"Node Type": "Seq Scan"[^}]*"Relation Name": "pg_proc"/s,
+	qr/"Node Type": "Seq Scan"[^}]*"Relation Name": "pg_class"/s,
 	"sequential scan logged, json mode");
 
 # Prepared query in JSON format.
@@ -160,4 +143,43 @@ sub query_log
 	qr/"Node Type": "Index Scan"[^}]*"Index Name": "pg_class_relname_nsp_index"/s,
 	"index scan logged, json mode");
 
+# Check that PGC_SUSET parameters can be set by non-superuser if granted,
+# otherwise not
+
+$node->safe_psql(
+	"postgres", q{
+CREATE USER regress_user1;
+GRANT SET ON PARAMETER auto_explain.log_format TO regress_user1;
+});
+
+$ENV{PGUSER} = "regress_user1";
+
+$log_contents = query_log(
+	$node,
+	"SELECT * FROM pg_database;",
+	{ "auto_explain.log_format" => "json" });
+
+like(
+	$log_contents,
+	qr/"Query Text": "SELECT \* FROM pg_database;"/,
+	"query text logged, json mode selected by non-superuser");
+
+$log_contents = query_log(
+	$node,
+	"SELECT * FROM pg_database;",
+	{ "auto_explain.log_level" => "log" });
+
+like(
+	$log_contents,
+	qr/WARNING:  permission denied to set parameter "auto_explain\.log_level"/,
+	"permission failure logged");
+
+$ENV{PGUSER} = undef;
+
+$node->safe_psql(
+	"postgres", q{
+REVOKE SET ON PARAMETER auto_explain.log_format FROM regress_user1;
+DROP USER regress_user1;
+});
+
 done_testing();