Refactor some code related to wait events "BufferPin" and "Extension"

The following changes are done:
- Addition of WaitEventBufferPin and WaitEventExtension, that hold a
list of wait events related to each category.
- Addition of two functions that encapsulate the list of wait events for
each category.
- Rename BUFFER_PIN to BUFFERPIN (only this wait event class used an
underscore, requiring a specific rule in the automation script).

These changes make a bit easier the automatic generation of all the code
and documentation related to wait events, as all the wait event
categories are now controlled by consistent structures and functions.

Author: Bertrand Drouvot
Discussion: https://postgr.es/m/c6f35117-4b20-4c78-1df5-d3056010dcf5@gmail.com
Discussion: https://postgr.es/m/77a86b3a-c4a8-5f5d-69b9-d70bbf2e9b98@gmail.com

3 files changed, 62 insertions, 8 deletions

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 3c59bbd04ea..a7e3b9bb1d3 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -4901,7 +4901,7 @@ LockBufferForCleanup(Buffer buffer)
 			SetStartupBufferPinWaitBufId(-1);
 		}
 		else
-			ProcWaitForSignal(PG_WAIT_BUFFER_PIN);
+			ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
 
 		/*
 		 * Remove flag marking us as waiter. Normally this will not be set
diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c
index 4c06741a69f..cc22d2e87cc 100644
--- a/src/backend/storage/ipc/standby.c
+++ b/src/backend/storage/ipc/standby.c
@@ -840,7 +840,7 @@ ResolveRecoveryConflictWithBufferPin(void)
 	 * SIGHUP signal handler, etc cannot do that because it uses the different
 	 * latch from that ProcWaitForSignal() waits on.
 	 */
-	ProcWaitForSignal(PG_WAIT_BUFFER_PIN);
+	ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
 
 	if (got_standby_delay_timeout)
 		SendRecoveryConflictWithBufferPin(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
diff --git a/src/backend/utils/activity/wait_event.c b/src/backend/utils/activity/wait_event.c
index 7940d646392..8572cf169ea 100644
--- a/src/backend/utils/activity/wait_event.c
+++ b/src/backend/utils/activity/wait_event.c
@@ -28,7 +28,9 @@
 
 
 static const char *pgstat_get_wait_activity(WaitEventActivity w);
+static const char *pgstat_get_wait_bufferpin(WaitEventBufferPin w);
 static const char *pgstat_get_wait_client(WaitEventClient w);
+static const char *pgstat_get_wait_extension(WaitEventExtension w);
 static const char *pgstat_get_wait_ipc(WaitEventIPC w);
 static const char *pgstat_get_wait_timeout(WaitEventTimeout w);
 static const char *pgstat_get_wait_io(WaitEventIO w);
@@ -90,7 +92,7 @@ pgstat_get_wait_event_type(uint32 wait_event_info)
 		case PG_WAIT_LOCK:
 			event_type = "Lock";
 			break;
-		case PG_WAIT_BUFFER_PIN:
+		case PG_WAIT_BUFFERPIN:
 			event_type = "BufferPin";
 			break;
 		case PG_WAIT_ACTIVITY:
@@ -147,9 +149,13 @@ pgstat_get_wait_event(uint32 wait_event_info)
 		case PG_WAIT_LOCK:
 			event_name = GetLockNameFromTagType(eventId);
 			break;
-		case PG_WAIT_BUFFER_PIN:
-			event_name = "BufferPin";
-			break;
+		case PG_WAIT_BUFFERPIN:
+			{
+				WaitEventBufferPin w = (WaitEventBufferPin) wait_event_info;
+
+				event_name = pgstat_get_wait_bufferpin(w);
+				break;
+			}
 		case PG_WAIT_ACTIVITY:
 			{
 				WaitEventActivity w = (WaitEventActivity) wait_event_info;
@@ -165,8 +171,12 @@ pgstat_get_wait_event(uint32 wait_event_info)
 				break;
 			}
 		case PG_WAIT_EXTENSION:
-			event_name = "Extension";
-			break;
+			{
+				WaitEventExtension w = (WaitEventExtension) wait_event_info;
+
+				event_name = pgstat_get_wait_extension(w);
+				break;
+			}
 		case PG_WAIT_IPC:
 			{
 				WaitEventIPC w = (WaitEventIPC) wait_event_info;
@@ -255,6 +265,28 @@ pgstat_get_wait_activity(WaitEventActivity w)
 }
 
 /* ----------
+ * pgstat_get_wait_bufferpin() -
+ *
+ * Convert WaitEventBufferPin to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_bufferpin(WaitEventBufferPin w)
+{
+	const char *event_name = "unknown wait event";
+
+	switch (w)
+	{
+		case WAIT_EVENT_BUFFER_PIN:
+			event_name = "BufferPin";
+			break;
+			/* no default case, so that compiler will warn */
+	}
+
+	return event_name;
+}
+
+/* ----------
  * pgstat_get_wait_client() -
  *
  * Convert WaitEventClient to string.
@@ -298,6 +330,28 @@ pgstat_get_wait_client(WaitEventClient w)
 }
 
 /* ----------
+ * pgstat_get_wait_extension() -
+ *
+ * Convert WaitEventExtension to string.
+ * ----------
+ */
+static const char *
+pgstat_get_wait_extension(WaitEventExtension w)
+{
+	const char *event_name = "unknown wait event";
+
+	switch (w)
+	{
+		case WAIT_EVENT_EXTENSION:
+			event_name = "Extension";
+			break;
+			/* no default case, so that compiler will warn */
+	}
+
+	return event_name;
+}
+
+/* ----------
  * pgstat_get_wait_ipc() -
  *
  * Convert WaitEventIPC to string.