0001-Fix-memory-leak-in-pgstat_progress_parallel_incr_par.patch

From 590712b4fea381a82cfaa9aa17bbe0f07ca0c16a Mon Sep 17 00:00:00 2001
From: Baji Shaik <baji.pgdev@gmail.com>
Date: Fri, 5 Jun 2026 12:40:18 -0500
Subject: [PATCH] Fix memory leak in pgstat_progress_parallel_incr_param()

When called from a parallel worker, pgstat_progress_parallel_incr_param()
calls initStringInfo() on a static StringInfoData and then immediately
calls pq_beginmessage(), which calls initStringInfo() again.  The second
call overwrites buf->data with a freshly palloc'd buffer, orphaning the
first one.  pq_endmessage() then frees only the second buffer, so each
call leaks ~1 kB into the per-worker memory context.

The leak is negligible by default, but with track_cost_delay_timing
enabled the parallel cost-delay reporting path fires once per second per
worker, so a long-running parallel vacuum leaks megabytes per worker.

Fix by initializing the static buffer once per process and using
pq_beginmessage_reuse()/pq_endmessage_reuse(), so the buffer is allocated
once and reused.

This is an oversight of f1889729dd3 ("Add new parallel message type to
progress reporting"); track_cost_delay_timing just makes it more visible.

Author: Baji Shaik <baji.pgdev@gmail.com>
---
 src/backend/utils/activity/backend_progress.c | 20 ++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/backend/utils/activity/backend_progress.c b/src/backend/utils/activity/backend_progress.c
index b0359771de5..0483741a80e 100644
--- a/src/backend/utils/activity/backend_progress.c
+++ b/src/backend/utils/activity/backend_progress.c
@@ -99,13 +99,23 @@ pgstat_progress_parallel_incr_param(int index, int64 incr)
 	if (IsParallelWorker())
 	{
 		static StringInfoData progress_message;
-
-		initStringInfo(&progress_message);
-
-		pq_beginmessage(&progress_message, PqMsg_Progress);
+		static bool progress_message_initialized = false;
+
+		/*
+		 * Initialize the message buffer once per process; pq_beginmessage_reuse()
+		 * and pq_endmessage_reuse() reset and reuse it on each call to avoid
+		 * palloc overhead.
+		 */
+		if (!progress_message_initialized)
+		{
+			initStringInfo(&progress_message);
+			progress_message_initialized = true;
+		}
+
+		pq_beginmessage_reuse(&progress_message, PqMsg_Progress);
 		pq_sendint32(&progress_message, index);
 		pq_sendint64(&progress_message, incr);
-		pq_endmessage(&progress_message);
+		pq_endmessage_reuse(&progress_message);
 	}
 	else
 		pgstat_progress_incr_param(index, incr);
-- 
2.50.1 (Apple Git-155)