Remove enum WaitEventExtension

This enum was used to determine the first ID to use when assigning a
custom wait event for extensions, which is always 1.  It was kept so
as it would be possible to add new in-core wait events in the category
"Extension".  There is no such thing currently, so let's remove this
enum until a case justifying it pops up.  This makes the code simpler
and easier to understand.

This has as effect to switch back autoprewarm.c to use PG_WAIT_EXTENSION
rather than WAIT_EVENT_EXTENSION, on par with v16 and older stable
branches.

Thinko in c9af054.

Reported-by: Peter Eisentraut
Discussion: https://postgr.es/m/195c6c45-abce-4331-be6a-e87724e1d060@eisentraut.org

Author: michaelpq

contrib/pg_prewarm/autoprewarm.c

@@ -226,7 +226,7 @@ autoprewarm_main(Datum main_arg)
 			(void) WaitLatch(MyLatch,
 							 WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
 							 -1L,
-							 WAIT_EVENT_EXTENSION);
+							 PG_WAIT_EXTENSION);
 		}
 		else
 		{
@@ -253,7 +253,7 @@ autoprewarm_main(Datum main_arg)
 			(void) WaitLatch(MyLatch,
 							 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
 							 delay_in_ms,
-							 WAIT_EVENT_EXTENSION);
+							 PG_WAIT_EXTENSION);
 		}
 
 		/* Reset the latch, loop. */

src/backend/utils/activity/wait_event.c

@@ -89,8 +89,7 @@ typedef struct WaitEventExtensionCounterData
 static WaitEventExtensionCounterData *WaitEventExtensionCounter;
 
 /* first event ID of custom wait events for extensions */
-#define NUM_BUILTIN_WAIT_EVENT_EXTENSION	\
-	(WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED - WAIT_EVENT_EXTENSION)
+#define WAIT_EVENT_EXTENSION_INITIAL_ID	1
 
 /* wait event info for extensions */
 #define WAIT_EVENT_EXTENSION_INFO(eventId)	(PG_WAIT_EXTENSION | eventId)
@@ -129,7 +128,7 @@ WaitEventExtensionShmemInit(void)
 	if (!found)
 	{
 		/* initialize the allocation counter and its spinlock. */
-		WaitEventExtensionCounter->nextId = NUM_BUILTIN_WAIT_EVENT_EXTENSION;
+		WaitEventExtensionCounter->nextId = WAIT_EVENT_EXTENSION_INITIAL_ID;
 		SpinLockInit(&WaitEventExtensionCounter->mutex);
 	}
 
@@ -244,7 +243,7 @@ GetWaitEventExtensionIdentifier(uint16 eventId)
 	WaitEventExtensionEntryById *entry;
 
 	/* Built-in event? */
-	if (eventId < NUM_BUILTIN_WAIT_EVENT_EXTENSION)
+	if (eventId < WAIT_EVENT_EXTENSION_INITIAL_ID)
 		return "Extension";
 
 	/* It is a user-defined wait event, so lookup hash table. */

src/include/utils/wait_event.h

@@ -53,12 +53,6 @@ extern PGDLLIMPORT uint32 *my_wait_event_info;
  *
  * The ID retrieved can be used with pgstat_report_wait_start() or equivalent.
  */
-typedef enum
-{
-	WAIT_EVENT_EXTENSION = PG_WAIT_EXTENSION,
-	WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED,
-} WaitEventExtension;
-
 extern void WaitEventExtensionShmemInit(void);
 extern Size WaitEventExtensionShmemSize(void);
 

src/tools/pgindent/typedefs.list

@@ -3100,7 +3100,6 @@ WaitEvent
 WaitEventActivity
 WaitEventBufferPin
 WaitEventClient
-WaitEventExtension
 WaitEventExtensionCounterData
 WaitEventExtensionEntryById
 WaitEventExtensionEntryByName