From 2641356ffacc0c69779a6252a8072f41521c0f3f Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 23 Apr 2025 15:52:24 +0900
Subject: [PATCH v3] psql: Fix assertion failure with pipeline mode

---
 src/bin/psql/common.c       | 17 +++++++++++++
 src/bin/psql/t/001_basic.pl | 49 +++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index 21d660a8961a..0aab02ee32e6 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 b0e4919d4d71..3cada3ba959b 100644
--- a/src/bin/psql/t/001_basic.pl
+++ b/src/bin/psql/t/001_basic.pl
@@ -483,4 +483,53 @@ 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()');
+my $log_location = -s $node->logfile;
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN;
+SELECT 'val1';
+\\syncpipeline
+\\getresults
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'protocol sync loss in pipeline: direct COPY, SELECT, sync and getresult'
+);
+$node->wait_for_log(
+	qr/FATAL: .*terminating connection because protocol synchronization was lost/,
+	$log_location);
+
+$log_location = -s $node->logfile;
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN \\bind \\sendpipeline
+SELECT 'val1' \\bind \\sendpipeline
+\\syncpipeline
+\\getresults
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'protocol sync loss in pipeline: bind COPY, SELECT, sync and getresult');
+$node->wait_for_log(
+	qr/FATAL: .*terminating connection because protocol synchronization was lost/,
+	$log_location);
+
+# This time, test without the \getresults.
+$log_location = -s $node->logfile;
+psql_fails_like(
+	$node,
+	qq{\\startpipeline
+COPY psql_pipeline FROM STDIN;
+SELECT 'val1';
+\\syncpipeline
+\\endpipeline},
+	qr/server closed the connection unexpectedly/,
+	'protocol sync loss in pipeline: COPY, SELECT and sync');
+$node->wait_for_log(
+	qr/FATAL: .*terminating connection because protocol synchronization was lost/,
+	$log_location);
+
 done_testing();
-- 
2.49.0