From 5d37f2616c82c6525d656149d383ef01a6d7518c Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Mon, 21 Apr 2025 15:17:43 +0900
Subject: [PATCH] psql: Fix assertion failure with pipeline mode

---
 src/bin/psql/common.c       | 17 ++++++++++++
 src/bin/psql/t/001_basic.pl | 55 ++++++++++++++++++++++++++++++++++---
 2 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index 21d660a8961..0aab02ee32e 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -1478,6 +1478,23 @@ discardAbortedPipelineResults(void)
 			 */
 			return res;
 		}
+		else if (res != NULL && result_status == PGRES_FATAL_ERROR)
+		{
+			/*
+			 * We have a fatal error sent by the backend and we can't recover
+			 * from this state. Instead, return the last fatal error and let
+			 * the outer loop handle it.
+			 */
+			PGresult   *fatal_res PG_USED_FOR_ASSERTS_ONLY;
+
+			/*
+			 * Fetch result to consume the end of the current query being
+			 * processed.
+			 */
+			fatal_res = PQgetResult(pset.db);
+			Assert(fatal_res == NULL);
+			return res;
+		}
 		else if (res == NULL)
 		{
 			/* A query was processed, decrement the counters */
diff --git a/src/bin/psql/t/001_basic.pl b/src/bin/psql/t/001_basic.pl
index 739cb439708..8d258c00c5e 100644
--- a/src/bin/psql/t/001_basic.pl
+++ b/src/bin/psql/t/001_basic.pl
@@ -34,11 +34,13 @@ sub psql_fails_like
 {
 	local $Test::Builder::Level = $Test::Builder::Level + 1;
 
-	my ($node, $sql, $expected_stderr, $test_name) = @_;
+	my ($node, $sql, $expected_stderr, $test_name, $replication) = @_;
+
+	# Use the context of a WAL sender, if requested by the caller.
+	$replication = '' unless defined($replication);
 
-	# Use the context of a WAL sender, some of the tests rely on that.
 	my ($ret, $stdout, $stderr) =
-	  $node->psql('postgres', $sql, replication => 'database');
+	  $node->psql('postgres', $sql, replication => $replication);
 
 	isnt($ret, 0, "$test_name: exit code not 0");
 	like($stderr, $expected_stderr, "$test_name: matches");
@@ -79,7 +81,8 @@ psql_fails_like(
 	$node,
 	'START_REPLICATION 0/0',
 	qr/unexpected PQresultStatus: 8$/,
-	'handling of unexpected PQresultStatus');
+	'handling of unexpected PQresultStatus',
+	'database');
 
 # test \timing
 psql_like(
@@ -481,4 +484,48 @@ psql_like($node, "copy (values ('foo'),('bar')) to stdout \\g | $pipe_cmd",
 my $c4 = slurp_file($g_file);
 like($c4, qr/foo.*bar/s);
 
+# Tests with pipelines.  These trigger FATAL failures in the backend,
+# so they cannot be tested through the SQL regression tests.
+$node->safe_psql('postgres', 'CREATE TABLE psql_pipeline()');
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN;
+SELECT 'val1';
+\\syncpipeline
+\\getresults
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'handling of protocol synchronization loss with pipelines');
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN \\bind \\sendpipeline
+SELECT 'val1' \\bind \\sendpipeline
+\\syncpipeline
+\\getresults
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'handling of protocol synchronization loss with pipelines');
+
+# This time, test without the \getresults
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN;
+SELECT 'val1';
+\\syncpipeline
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'handling of protocol synchronization loss with pipelines');
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN \\bind \\sendpipeline
+SELECT 'val1' \\bind \\sendpipeline
+\\syncpipeline
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'handling of protocol synchronization loss with pipelines');
+
 done_testing();
-- 
2.39.5 (Apple Git-154)