Fix TAP test for remove_temp_files_after_crash

The test included in cd91de0d had two simple flaws.

Firstly, the number of rows was low and on some platforms (e.g. 32-bit)
the sort did not require on-disk sort, so on those machines it was not
testing the automatic removal.  The test was however failing, because
without any temporary files the base/pgsql_tmp directory was not even
created.  Fixed by increasing the rowcount to 5000, which should be high
engough on any platform.

Secondly, the test used a simple sleep to wait for the temporary file to
be created.  This is obviously problematic, because on slow machines (or
with valgrind, CLOBBER_CACHE_ALWAYS etc.) it may take a while to create
the temporary file.  But we also want the tests run reasonably fast.
Fixed by instead relying on a UNIQUE constraint, blocking the query that
created the temporary file.

Author: Euler Taveira
Reviewed-by: Tomas Vondra
Discussion: https://postgr.es/m/CAH503wDKdYzyq7U-QJqGn%3DGm6XmoK%2B6_6xTJ-Yn5WSvoHLY1Ww%40mail.gmail.com

src/test/recovery/t/022_crash_temp_files.pl

@@ -5,7 +5,6 @@ use PostgresNode;
 use TestLib;
 use Test::More;
 use Config;
-use Time::HiRes qw(usleep);
 
 plan tests => 9;
 
@@ -33,8 +32,7 @@ $node->safe_psql(
 # create table, insert rows
 $node->safe_psql(
 	'postgres',
-	q[CREATE TABLE tab_crash (a text);
-		INSERT INTO tab_crash (a) SELECT gen_random_uuid() FROM generate_series(1, 500);]);
+	q[CREATE TABLE tab_crash (a integer UNIQUE);]);
 
 # Run psql, keeping session alive, so we have an alive backend to kill.
 my ($killme_stdin, $killme_stdout, $killme_stderr) = ('', '', '');
@@ -62,6 +60,32 @@ chomp($pid);
 $killme_stdout = '';
 $killme_stderr = '';
 
+# Open a 2nd session that will block the 1st one, using the UNIQUE constraint.
+# This will prevent removal of the temporary file created by the 1st session.
+my ($killme_stdin2, $killme_stdout2, $killme_stderr2) = ('', '', '');
+my $killme2 = IPC::Run::start(
+	[
+		'psql', '-X', '-qAt', '-v', 'ON_ERROR_STOP=1', '-f', '-', '-d',
+		$node->connstr('postgres')
+	],
+	'<',
+	\$killme_stdin2,
+	'>',
+	\$killme_stdout2,
+	'2>',
+	\$killme_stderr2,
+	$psql_timeout);
+
+# Insert one tuple and leave the transaction open
+$killme_stdin2 .= q[
+BEGIN;
+SELECT $$insert-tuple-to-lock-next-insert$$;
+INSERT INTO tab_crash (a) VALUES(1);
+];
+pump_until($killme2, \$killme_stdout2, qr/insert-tuple-to-lock-next-insert/m);
+$killme_stdout2 = '';
+$killme_stderr2 = '';
+
 # Run the query that generates a temporary file and that will be killed before
 # it finishes. Since the query that generates the temporary file does not
 # return before the connection is killed, use a SELECT before to trigger
@@ -69,22 +93,20 @@ $killme_stderr = '';
 $killme_stdin .= q[
 BEGIN;
 SELECT $$in-progress-before-sigkill$$;
-WITH foo AS (SELECT a FROM tab_crash ORDER BY a) SELECT a, pg_sleep(1) FROM foo;
+INSERT INTO tab_crash (a) SELECT i FROM generate_series(1, 5000) s(i);
 ];
 ok(pump_until($killme, \$killme_stdout, qr/in-progress-before-sigkill/m),
-	'select in-progress-before-sigkill');
+	'insert in-progress-before-sigkill');
 $killme_stdout = '';
 $killme_stderr = '';
 
-# Wait some time so the temporary file is generated by SELECT
-usleep(10_000);
-
 # Kill with SIGKILL
 my $ret = TestLib::system_log('pg_ctl', 'kill', 'KILL', $pid);
 is($ret, 0, 'killed process with KILL');
 
 # Close psql session
 $killme->finish;
+$killme2->finish;
 
 # Wait till server restarts
 $node->poll_query_until('postgres', 'SELECT 1', '1');
@@ -118,6 +140,20 @@ chomp($pid);
 $killme_stdout = '';
 $killme_stderr = '';
 
+# Restart the 2nd psql session
+($killme_stdin2, $killme_stdout2, $killme_stderr2) = ('', '', '');
+$killme2->run();
+
+# Insert one tuple and leave the transaction open
+$killme_stdin2 .= q[
+BEGIN;
+SELECT $$insert-tuple-to-lock-next-insert$$;
+INSERT INTO tab_crash (a) VALUES(1);
+];
+pump_until($killme2, \$killme_stdout2, qr/insert-tuple-to-lock-next-insert/m);
+$killme_stdout2 = '';
+$killme_stderr2 = '';
+
 # Run the query that generates a temporary file and that will be killed before
 # it finishes. Since the query that generates the temporary file does not
 # return before the connection is killed, use a SELECT before to trigger
@@ -125,22 +161,20 @@ $killme_stderr = '';
 $killme_stdin .= q[
 BEGIN;
 SELECT $$in-progress-before-sigkill$$;
-WITH foo AS (SELECT a FROM tab_crash ORDER BY a) SELECT a, pg_sleep(1) FROM foo;
+INSERT INTO tab_crash (a) SELECT i FROM generate_series(1, 5000) s(i);
 ];
 ok(pump_until($killme, \$killme_stdout, qr/in-progress-before-sigkill/m),
-	'select in-progress-before-sigkill');
+	'insert in-progress-before-sigkill');
 $killme_stdout = '';
 $killme_stderr = '';
 
-# Wait some time so the temporary file is generated by SELECT
-usleep(10_000);
-
 # Kill with SIGKILL
 $ret = TestLib::system_log('pg_ctl', 'kill', 'KILL', $pid);
 is($ret, 0, 'killed process with KILL');
 
 # Close psql session
 $killme->finish;
+$killme2->finish;
 
 # Wait till server restarts
 $node->poll_query_until('postgres', 'SELECT 1', '1');