0001-Expose-checkpoint-reason-in-completion-log-messages.patch

From 6987dad63e07700bbde9e095516f880719b9c729 Mon Sep 17 00:00:00 2001
From: Soumya <soumyamurali.work@gmail.com>
Date: Wed, 14 Jan 2026 15:32:29 +0530
Subject: [PATCH] Expose checkpoint reason in completion log messages

Signed-off-by: Soumya <soumyamurali.work@gmail.com>
---
 src/backend/access/transam/xlog.c         | 79 ++++++++++++++++-------
 src/test/recovery/t/019_replslot_limit.pl |  2 +-
 2 files changed, 56 insertions(+), 25 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 22d0a2e8c3..881e656f25 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6714,6 +6714,50 @@ 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 *
+CheckpointFlagsString(int flags)
+{
+	static char buf[128];
+	bool		first = true;
+
+	buf[0] = '\0';
+
+#define APPEND_REASON(str)				\
+	do									\
+	{                                   \
+		if (!first)                     \
+			strcat(buf, " ");           \
+		strcat(buf, (str));             \
+		first = false;                  \
+	} while (0)
+
+	if (flags & CHECKPOINT_IS_SHUTDOWN)
+		APPEND_REASON("shutdown");
+	if (flags & CHECKPOINT_END_OF_RECOVERY)
+		APPEND_REASON("end-of-recovery");
+	if (flags & CHECKPOINT_FAST)
+		APPEND_REASON("fast");
+	if (flags & CHECKPOINT_FORCE)
+		APPEND_REASON("force");
+	if (flags & CHECKPOINT_WAIT)
+		APPEND_REASON("wait");
+	if (flags & CHECKPOINT_CAUSE_XLOG)
+		APPEND_REASON("wal");
+	if (flags & CHECKPOINT_CAUSE_TIME)
+		APPEND_REASON("time");
+	if (flags & CHECKPOINT_FLUSH_UNLOGGED)
+		APPEND_REASON("flush-unlogged");
+
+#undef APPEND_REASON
+
+	return buf;
+}
+
 /*
  * Log start of a checkpoint.
  */
@@ -6723,34 +6767,19 @@ LogCheckpointStart(int flags, bool restartpoint)
 	if (restartpoint)
 		ereport(LOG,
 		/* translator: the placeholders show checkpoint options */
-				(errmsg("restartpoint 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("restartpoint starting: %s",
+						CheckpointFlagsString(flags))));
 	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",
+						CheckpointFlagsString(flags))));
 }
 
 /*
  * Log end of a checkpoint.
  */
 static void
-LogCheckpointEnd(bool restartpoint)
+LogCheckpointEnd(bool restartpoint, int flags)
 {
 	long		write_msecs,
 				sync_msecs,
@@ -6800,12 +6829,13 @@ LogCheckpointEnd(bool restartpoint)
 	 */
 	if (restartpoint)
 		ereport(LOG,
-				(errmsg("restartpoint complete: wrote %d buffers (%.1f%%), "
+				(errmsg("restartpoint 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",
+						CheckpointFlagsString(flags),
 						CheckpointStats.ckpt_bufs_written,
 						(double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers,
 						CheckpointStats.ckpt_slru_written,
@@ -6824,12 +6854,13 @@ 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",
+						CheckpointFlagsString(flags),
 						CheckpointStats.ckpt_bufs_written,
 						(double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers,
 						CheckpointStats.ckpt_slru_written,
@@ -7418,7 +7449,7 @@ CreateCheckPoint(int flags)
 		TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning());
 
 	/* Real work is done; log and update stats. */
-	LogCheckpointEnd(false);
+	LogCheckpointEnd(false, flags);
 
 	/* Reset the process title */
 	update_checkpoint_display(flags, false, true);
@@ -7886,7 +7917,7 @@ CreateRestartPoint(int flags)
 		TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning());
 
 	/* Real work is done; log and update stats. */
-	LogCheckpointEnd(true);
+	LogCheckpointEnd(true, flags);
 
 	/* Reset the process title */
 	update_checkpoint_display(flags, true, true);
diff --git a/src/test/recovery/t/019_replslot_limit.pl b/src/test/recovery/t/019_replslot_limit.pl
index 6468784b83..ad2088ef3a 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("checkpoint complete:", $logstart))
 	{
 		$checkpoint_ended = 1;
 		last;
-- 
2.34.1