PG18-Fix-specinsert-leak-in-ReorderBufferProcessTXN-error-path.txt

From 64deae15dc57ac7083fd5d1967f0b8a83e648b56 Mon Sep 17 00:00:00 2001
From: Vishal Prasanna <vishal.g@zohocorp.com>
Date: Mon, 9 Mar 2026 00:46:12 +0530
Subject: [PATCH] Fix specinsert leak in ReorderBufferProcessTXN error path

---
 .../replication/logical/reorderbuffer.c       | 20 ++++-----
 src/test/subscription/t/100_bugs.pl           | 45 +++++++++++++++++++
 2 files changed, 54 insertions(+), 11 deletions(-)

diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 11139a910b8..57e1ae2441b 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2164,8 +2164,7 @@ static void
 ReorderBufferResetTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 					  Snapshot snapshot_now,
 					  CommandId command_id,
-					  XLogRecPtr last_lsn,
-					  ReorderBufferChange *specinsert)
+					  XLogRecPtr last_lsn)
 {
 	/* Discard the changes that we just streamed */
 	ReorderBufferTruncateTXN(rb, txn, rbtxn_is_prepared(txn));
@@ -2173,13 +2172,6 @@ ReorderBufferResetTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 	/* Free all resources allocated for toast reconstruction */
 	ReorderBufferToastReset(rb, txn);
 
-	/* Return the spec insert change if it is not NULL */
-	if (specinsert != NULL)
-	{
-		ReorderBufferFreeChange(rb, specinsert, true);
-		specinsert = NULL;
-	}
-
 	/*
 	 * For the streaming case, stop the stream and remember the command ID and
 	 * snapshot for the streaming run.
@@ -2753,6 +2745,13 @@ ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 		if (using_subtxn)
 			RollbackAndReleaseCurrentSubTransaction();
 
+		/* Free the specinsert change before freeing the ReorderBufferTXN */
+		if (specinsert != NULL)
+		{
+			ReorderBufferFreeChange(rb, specinsert, true);
+			specinsert = NULL;
+		}
+
 		/*
 		 * The error code ERRCODE_TRANSACTION_ROLLBACK indicates a concurrent
 		 * abort of the (sub)transaction we are streaming or preparing. We
@@ -2786,8 +2785,7 @@ ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 
 			/* Reset the TXN so that it is allowed to stream remaining data. */
 			ReorderBufferResetTXN(rb, txn, snapshot_now,
-								  command_id, prev_lsn,
-								  specinsert);
+								  command_id, prev_lsn);
 		}
 		else
 		{
diff --git a/src/test/subscription/t/100_bugs.pl b/src/test/subscription/t/100_bugs.pl
index 50223054918..df6b2e1296d 100644
--- a/src/test/subscription/t/100_bugs.pl
+++ b/src/test/subscription/t/100_bugs.pl
@@ -605,4 +605,49 @@ $node_publisher->safe_psql('postgres', "DROP DATABASE regress_db");
 
 $node_publisher->stop('fast');
 
+# https://postgr.es/m/19c7623e882.4080fd5426212.311756747309556767%40zohocorp.com
+
+# The bug was that when an ERROR was raised while processing an INSERT ... ON
+# CONFLICT statement, the decoded change misses to be free'd. This can cause an
+# assertion failure if enabled.
+
+$node_publisher->rotate_logfile();
+$node_publisher->start();
+
+# Create a publication with the zero-division row filter. It always throws an
+# ERROR before publishing changes, when the filter is evaluated.
+$node_publisher->safe_psql(
+	'postgres', qq(
+	CREATE TABLE tab_upsert (a INT PRIMARY KEY, b INT);
+	CREATE PUBLICATION pub_rowfilter_error FOR TABLE tab_upsert WHERE ((a / 0) > 0);
+	SELECT * FROM pg_create_logical_replication_slot('upsert_slot', 'pgoutput');
+	INSERT INTO tab_upsert (a, b) VALUES (1, 1)
+		ON CONFLICT(a) DO UPDATE SET b = excluded.b;
+));
+
+# Decode the changes with a publication whose row filter causes a
+# division by zero error, and verify that the logical decoder doesn't crash.
+($ret, $stdout, $stderr) = $node_publisher->psql(
+	'postgres', qq(
+	SELECT *
+	FROM pg_logical_slot_peek_binary_changes(
+		'upsert_slot',
+		NULL,
+		NULL,
+		'proto_version', '1',
+		'publication_names', 'pub_rowfilter_error'
+	);
+));
+
+ok( $stderr =~ qr/division by zero/,
+	'peek logical changes with row filter causing division by zero throws error'
+);
+
+# Clean up
+$node_publisher->safe_psql('postgres', "SELECT pg_drop_replication_slot('upsert_slot')");
+$node_publisher->safe_psql('postgres', "DROP PUBLICATION pub_rowfilter_error");
+$node_publisher->safe_psql('postgres', "DROP TABLE tab_upsert");
+
+$node_publisher->stop('fast');
+
 done_testing();
-- 
2.50.1 (Apple Git-155)