Add num_done counter to the pg_stat_checkpointer view.

Checkpoints can be skipped when the server is idle. The existing num_timed and
num_requested counters in pg_stat_checkpointer track both completed and
skipped checkpoints, but there was no way to count only the completed ones.

This commit introduces the num_done counter, which tracks only completed
checkpoints, making it easier to see how many were actually performed.

Bump catalog version.

Author: Anton A. Melnikov
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/9ea77f40-818d-4841-9dee-158ac8f6e690@oss.nttdata.com

1 files changed, 25 insertions, 14 deletions

diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index eeb73c85726..9087e3f8db1 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -460,10 +460,7 @@ CheckpointerMain(char *startup_data, size_t startup_data_len)
 			 * Do the checkpoint.
 			 */
 			if (!do_restartpoint)
-			{
-				CreateCheckPoint(flags);
-				ckpt_performed = true;
-			}
+				ckpt_performed = CreateCheckPoint(flags);
 			else
 				ckpt_performed = CreateRestartPoint(flags);
 
@@ -484,7 +481,7 @@ CheckpointerMain(char *startup_data, size_t startup_data_len)
 
 			ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
 
-			if (ckpt_performed)
+			if (!do_restartpoint)
 			{
 				/*
 				 * Note we record the checkpoint start time not end time as
@@ -493,18 +490,32 @@ CheckpointerMain(char *startup_data, size_t startup_data_len)
 				 */
 				last_checkpoint_time = now;
 
-				if (do_restartpoint)
-					PendingCheckpointerStats.restartpoints_performed++;
+				if (ckpt_performed)
+					PendingCheckpointerStats.num_performed++;
 			}
 			else
 			{
-				/*
-				 * We were not able to perform the restartpoint (checkpoints
-				 * throw an ERROR in case of error).  Most likely because we
-				 * have not received any new checkpoint WAL records since the
-				 * last restartpoint. Try again in 15 s.
-				 */
-				last_checkpoint_time = now - CheckPointTimeout + 15;
+				if (ckpt_performed)
+				{
+					/*
+					 * The same as for checkpoint. Please see the
+					 * corresponding comment.
+					 */
+					last_checkpoint_time = now;
+
+					PendingCheckpointerStats.restartpoints_performed++;
+				}
+				else
+				{
+					/*
+					 * We were not able to perform the restartpoint
+					 * (checkpoints throw an ERROR in case of error).  Most
+					 * likely because we have not received any new checkpoint
+					 * WAL records since the last restartpoint. Try again in
+					 * 15 s.
+					 */
+					last_checkpoint_time = now - CheckPointTimeout + 15;
+				}
 			}
 
 			ckpt_active = false;