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

contrib/dblink/dblink.c

@@ -203,7 +203,7 @@ dblink_get_conn(char *conname_or_str,
 		dblink_connstr_check(connstr);
 
 		/* OK to make connection */
-		conn = libpqsrv_connect(connstr, PG_WAIT_EXTENSION);
+		conn = libpqsrv_connect(connstr, WAIT_EVENT_EXTENSION);
 
 		if (PQstatus(conn) == CONNECTION_BAD)
 		{
@@ -293,7 +293,7 @@ dblink_connect(PG_FUNCTION_ARGS)
 	dblink_connstr_check(connstr);
 
 	/* OK to make connection */
-	conn = libpqsrv_connect(connstr, PG_WAIT_EXTENSION);
+	conn = libpqsrv_connect(connstr, WAIT_EVENT_EXTENSION);
 
 	if (PQstatus(conn) == CONNECTION_BAD)
 	{

contrib/pg_prewarm/autoprewarm.c

@@ -237,7 +237,7 @@ autoprewarm_main(Datum main_arg)
 			(void) WaitLatch(MyLatch,
 							 WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
 							 -1L,
-							 PG_WAIT_EXTENSION);
+							 WAIT_EVENT_EXTENSION);
 		}
 		else
 		{
@@ -264,7 +264,7 @@ autoprewarm_main(Datum main_arg)
 			(void) WaitLatch(MyLatch,
 							 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
 							 delay_in_ms,
-							 PG_WAIT_EXTENSION);
+							 WAIT_EVENT_EXTENSION);
 		}
 
 		/* Reset the latch, loop. */

contrib/postgres_fdw/connection.c

@@ -530,7 +530,7 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
 		/* OK to make connection */
 		conn = libpqsrv_connect_params(keywords, values,
 									   false,	/* expand_dbname */
-									   PG_WAIT_EXTENSION);
+									   WAIT_EVENT_EXTENSION);
 
 		if (!conn || PQstatus(conn) != CONNECTION_OK)
 			ereport(ERROR,
@@ -863,7 +863,7 @@ pgfdw_get_result(PGconn *conn, const char *query)
 									   WL_LATCH_SET | WL_SOCKET_READABLE |
 									   WL_EXIT_ON_PM_DEATH,
 									   PQsocket(conn),
-									   -1L, PG_WAIT_EXTENSION);
+									   -1L, WAIT_EVENT_EXTENSION);
 				ResetLatch(MyLatch);
 
 				CHECK_FOR_INTERRUPTS();
@@ -1567,7 +1567,7 @@ pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime, PGresult **result,
 									   WL_LATCH_SET | WL_SOCKET_READABLE |
 									   WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
 									   PQsocket(conn),
-									   cur_timeout, PG_WAIT_EXTENSION);
+									   cur_timeout, WAIT_EVENT_EXTENSION);
 				ResetLatch(MyLatch);
 
 				CHECK_FOR_INTERRUPTS();

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

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);

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;
@@ -254,6 +264,28 @@ pgstat_get_wait_activity(WaitEventActivity w)
 	return event_name;
 }
 
+/* ----------
+ * 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() -
  *
@@ -297,6 +329,28 @@ pgstat_get_wait_client(WaitEventClient w)
 	return event_name;
 }
 
+/* ----------
+ * 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() -
  *

src/include/utils/wait_event.h

@@ -17,7 +17,7 @@
  */
 #define PG_WAIT_LWLOCK				0x01000000U
 #define PG_WAIT_LOCK				0x03000000U
-#define PG_WAIT_BUFFER_PIN			0x04000000U
+#define PG_WAIT_BUFFERPIN			0x04000000U
 #define PG_WAIT_ACTIVITY			0x05000000U
 #define PG_WAIT_CLIENT				0x06000000U
 #define PG_WAIT_EXTENSION			0x07000000U
@@ -50,6 +50,15 @@ typedef enum
 	WAIT_EVENT_WAL_WRITER_MAIN
 } WaitEventActivity;
 
+/* ----------
+ * Wait Events - BUFFERPIN
+ * ----------
+ */
+typedef enum
+{
+	WAIT_EVENT_BUFFER_PIN = PG_WAIT_BUFFERPIN
+} WaitEventBufferPin;
+
 /* ----------
  * Wait Events - Client
  *
@@ -70,6 +79,15 @@ typedef enum
 	WAIT_EVENT_WAL_SENDER_WRITE_DATA,
 } WaitEventClient;
 
+/* ----------
+ * Wait Events - EXTENSION
+ * ----------
+ */
+typedef enum
+{
+	WAIT_EVENT_EXTENSION = PG_WAIT_EXTENSION
+} WaitEventExtension;
+
 /* ----------
  * Wait Events - IPC
  *

src/test/modules/test_shm_mq/setup.c

@@ -280,7 +280,7 @@ wait_for_workers_to_become_ready(worker_state *wstate,
 
 		/* Wait to be signaled. */
 		(void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
-						 PG_WAIT_EXTENSION);
+						 WAIT_EVENT_EXTENSION);
 
 		/* Reset the latch so we don't spin. */
 		ResetLatch(MyLatch);

src/test/modules/test_shm_mq/test.c

@@ -232,7 +232,7 @@ test_shm_mq_pipelined(PG_FUNCTION_ARGS)
 			 * for us to do.
 			 */
 			(void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
-							 PG_WAIT_EXTENSION);
+							 WAIT_EVENT_EXTENSION);
 			ResetLatch(MyLatch);
 			CHECK_FOR_INTERRUPTS();
 		}

src/test/modules/worker_spi/worker_spi.c

@@ -199,7 +199,7 @@ worker_spi_main(Datum main_arg)
 		(void) WaitLatch(MyLatch,
 						 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
 						 worker_spi_naptime * 1000L,
-						 PG_WAIT_EXTENSION);
+						 WAIT_EVENT_EXTENSION);
 		ResetLatch(MyLatch);
 
 		CHECK_FOR_INTERRUPTS();

src/tools/pgindent/typedefs.list

@@ -2986,7 +2986,9 @@ WSANETWORKEVENTS
 WSAPROTOCOL_INFO
 WaitEvent
 WaitEventActivity
+WaitEventBufferPin
 WaitEventClient
+WaitEventExtension
 WaitEventIO
 WaitEventIPC
 WaitEventSet