Avoid 037_invalid_database.pl hang under debug_discard_caches.

Back-patch to v12 (all supported versions).

diff --git a/src/test/recovery/t/037_invalid_database.pl b/src/test/recovery/t/037_invalid_database.pl
index 47f524be4ccdaeebb98ec5e766c4c54d7b9a4195..6d1c71179642178b3550013b2920a15d75f16e53 100644 (file)
--- a/src/test/recovery/t/037_invalid_database.pl
+++ b/src/test/recovery/t/037_invalid_database.pl
@@ -88,7 +88,10 @@ is($node->psql('postgres', 'DROP DATABASE regression_invalid'),
 # Test that interruption of DROP DATABASE is handled properly. To ensure the
 # interruption happens at the appropriate moment, we lock pg_tablespace. DROP
 # DATABASE scans pg_tablespace once it has reached the "irreversible" part of
-# dropping the database, making it a suitable point to wait.
+# dropping the database, making it a suitable point to wait.  Since relcache
+# init reads pg_tablespace, establish each connection before locking.  This
+# avoids a connection-time hang with debug_discard_caches.
+my $cancel = $node->background_psql('postgres', on_error_stop => 1);
 my $bgpsql = $node->background_psql('postgres', on_error_stop => 0);
 my $pid = $bgpsql->query('SELECT pg_backend_pid()');
 
@@ -104,14 +107,19 @@ ok( $bgpsql->query_safe(
 # Try to drop. This will wait due to the still held lock.
 $bgpsql->query_until(qr//, "DROP DATABASE regression_invalid_interrupt;\n");
 
-# Ensure we're waiting for the lock
-$node->poll_query_until('postgres',
-   qq(SELECT EXISTS(SELECT * FROM pg_locks WHERE NOT granted AND relation = 'pg_tablespace'::regclass AND mode = 'AccessShareLock');)
-);
 
-# and finally interrupt the DROP DATABASE
-ok($node->safe_psql('postgres', "SELECT pg_cancel_backend($pid)"),
+# Once the DROP DATABASE is waiting for the lock, interrupt it.
+ok( $cancel->query_safe(
+       qq(
+   DO \$\$
+   BEGIN
+       WHILE NOT EXISTS(SELECT * FROM pg_locks WHERE NOT granted AND relation = 'pg_tablespace'::regclass AND mode = 'AccessShareLock') LOOP
+           PERFORM pg_sleep(.1);
+       END LOOP;
+   END\$\$;
+   SELECT pg_cancel_backend($pid);)),
    "canceling DROP DATABASE");
+$cancel->quit();
 
 # wait for cancellation to be processed
 ok( pump_until(
@@ -120,7 +128,8 @@ ok( pump_until(
    "cancel processed");
 $bgpsql->{stderr} = '';
 
-# verify that connection to the database aren't allowed
+# Verify that connections to the database aren't allowed.  The backend checks
+# this before relcache init, so the lock won't interfere.
 is($node->psql('regression_invalid_interrupt', ''),
    2, "can't connect to invalid_interrupt database");