From 0204328b225d5641a13e3e6f4c373622df31a398 Mon Sep 17 00:00:00 2001
From: Soumya <soumyamurali.work@gmail.com>
Date: Thu, 8 Jan 2026 11:42:23 +0530
Subject: [PATCH] Expose checkpoint reason in checkpoint completion log
 messages

Signed-off-by: Soumya <soumyamurali.work@gmail.com>
---
 src/backend/access/transam/xlog.c         | 51 ++++++++++++++++++-----
 src/test/recovery/t/019_replslot_limit.pl |  2 +-
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 22d0a2e8c3..9f7439f9a2 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -203,6 +203,8 @@ const struct config_enum_entry archive_mode_options[] = {
 	{NULL, 0, false}
 };
 
+static char checkpoint_reason_str[128];
+
 /*
  * Statistics for current checkpoint are collected in this global struct.
  * Because only the checkpointer or a stand-alone backend can perform
@@ -6714,12 +6716,47 @@ ShutdownXLOG(int code, Datum arg)
 	}
 }
 
+/*
+ * Format checkpoint reason flags consistently for log messages.
+ * The returned string is suitable for inclusion after
+ * "checkpoint starting:" or inside "checkpoint complete (...)".
+ */
+static const char *
+CheckpointReasonString(int flags)
+{
+	static char buf[128];
+
+	buf[0] = '\0';
+
+	if (flags & CHECKPOINT_IS_SHUTDOWN)
+		strcat(buf, " shutdown");
+	if (flags & CHECKPOINT_END_OF_RECOVERY)
+		strcat(buf, " end-of-recovery");
+	if (flags & CHECKPOINT_FAST)
+		strcat(buf, " fast");
+	if (flags & CHECKPOINT_FORCE)
+		strcat(buf, " force");
+	if (flags & CHECKPOINT_WAIT)
+		strcat(buf, " wait");
+	if (flags & CHECKPOINT_CAUSE_XLOG)
+		strcat(buf, " wal");
+	if (flags & CHECKPOINT_CAUSE_TIME)
+		strcat(buf, " time");
+	if (flags & CHECKPOINT_FLUSH_UNLOGGED)
+		strcat(buf, " flush-unlogged");
+
+	return buf;
+}
+
 /*
  * Log start of a checkpoint.
  */
 static void
 LogCheckpointStart(int flags, bool restartpoint)
 {
+	strlcpy(checkpoint_reason_str,
+        	CheckpointReasonString(flags),
+        	sizeof(checkpoint_reason_str));
 	if (restartpoint)
 		ereport(LOG,
 		/* translator: the placeholders show checkpoint options */
@@ -6734,16 +6771,7 @@ LogCheckpointStart(int flags, bool restartpoint)
 						(flags & CHECKPOINT_FLUSH_UNLOGGED) ? " flush-unlogged" : "")));
 	else
 		ereport(LOG,
-		/* translator: the placeholders show checkpoint options */
-				(errmsg("checkpoint starting:%s%s%s%s%s%s%s%s",
-						(flags & CHECKPOINT_IS_SHUTDOWN) ? " shutdown" : "",
-						(flags & CHECKPOINT_END_OF_RECOVERY) ? " end-of-recovery" : "",
-						(flags & CHECKPOINT_FAST) ? " fast" : "",
-						(flags & CHECKPOINT_FORCE) ? " force" : "",
-						(flags & CHECKPOINT_WAIT) ? " wait" : "",
-						(flags & CHECKPOINT_CAUSE_XLOG) ? " wal" : "",
-						(flags & CHECKPOINT_CAUSE_TIME) ? " time" : "",
-						(flags & CHECKPOINT_FLUSH_UNLOGGED) ? " flush-unlogged" : "")));
+        		(errmsg("checkpoint starting:%s", checkpoint_reason_str)));
 }
 
 /*
@@ -6824,12 +6852,13 @@ LogCheckpointEnd(bool restartpoint)
 						LSN_FORMAT_ARGS(ControlFile->checkPointCopy.redo))));
 	else
 		ereport(LOG,
-				(errmsg("checkpoint complete: wrote %d buffers (%.1f%%), "
+				(errmsg("checkpoint complete (%s): wrote %d buffers (%.1f%%), "
 						"wrote %d SLRU buffers; %d WAL file(s) added, "
 						"%d removed, %d recycled; write=%ld.%03d s, "
 						"sync=%ld.%03d s, total=%ld.%03d s; sync files=%d, "
 						"longest=%ld.%03d s, average=%ld.%03d s; distance=%d kB, "
 						"estimate=%d kB; lsn=%X/%08X, redo lsn=%X/%08X",
+						checkpoint_reason_str,
 						CheckpointStats.ckpt_bufs_written,
 						(double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers,
 						CheckpointStats.ckpt_slru_written,
diff --git a/src/test/recovery/t/019_replslot_limit.pl b/src/test/recovery/t/019_replslot_limit.pl
index 6468784b83..ccc363157e 100644
--- a/src/test/recovery/t/019_replslot_limit.pl
+++ b/src/test/recovery/t/019_replslot_limit.pl
@@ -203,7 +203,7 @@ is($result, "rep1|f|t|lost|",
 my $checkpoint_ended = 0;
 for (my $i = 0; $i < 10 * $PostgreSQL::Test::Utils::timeout_default; $i++)
 {
-	if ($node_primary->log_contains("checkpoint complete: ", $logstart))
+	if ($node_primary->log_contains(qr/checkpoint complete(?: \([^)]*\))?:/, $logstart))
 	{
 		$checkpoint_ended = 1;
 		last;
-- 
2.34.1