Add BackendType for standalone backends

All backends should have a BackendType to enable statistics reporting
per BackendType.

Add a new BackendType for standalone backends, B_STANDALONE_BACKEND (and
alphabetize the BackendTypes). Both the bootstrap backend and single
user mode backends will have BackendType B_STANDALONE_BACKEND.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/CAAKRu_aaq33UnG4TXq3S-OSXGWj1QGf0sU%2BECH4tNwGFNERkZA%40mail.gmail.com

src/backend/utils/init/miscinit.c

@@ -176,6 +176,8 @@ InitStandaloneProcess(const char *argv0)
 {
 	Assert(!IsPostmasterEnvironment);
 
+	MyBackendType = B_STANDALONE_BACKEND;
+
 	/*
 	 * Start our win32 signal implementation
 	 */
@@ -255,6 +257,9 @@ GetBackendTypeDesc(BackendType backendType)
 		case B_INVALID:
 			backendDesc = "not initialized";
 			break;
+		case B_ARCHIVER:
+			backendDesc = "archiver";
+			break;
 		case B_AUTOVAC_LAUNCHER:
 			backendDesc = "autovacuum launcher";
 			break;
@@ -273,6 +278,12 @@ GetBackendTypeDesc(BackendType backendType)
 		case B_CHECKPOINTER:
 			backendDesc = "checkpointer";
 			break;
+		case B_LOGGER:
+			backendDesc = "logger";
+			break;
+		case B_STANDALONE_BACKEND:
+			backendDesc = "standalone backend";
+			break;
 		case B_STARTUP:
 			backendDesc = "startup";
 			break;
@@ -285,12 +296,6 @@ GetBackendTypeDesc(BackendType backendType)
 		case B_WAL_WRITER:
 			backendDesc = "walwriter";
 			break;
-		case B_ARCHIVER:
-			backendDesc = "archiver";
-			break;
-		case B_LOGGER:
-			backendDesc = "logger";
-			break;
 	}
 
 	return backendDesc;

src/include/miscadmin.h

@@ -316,18 +316,19 @@ extern void SwitchBackToLocalLatch(void);
 typedef enum BackendType
 {
 	B_INVALID = 0,
+	B_ARCHIVER,
 	B_AUTOVAC_LAUNCHER,
 	B_AUTOVAC_WORKER,
 	B_BACKEND,
 	B_BG_WORKER,
 	B_BG_WRITER,
 	B_CHECKPOINTER,
+	B_LOGGER,
+	B_STANDALONE_BACKEND,
 	B_STARTUP,
 	B_WAL_RECEIVER,
 	B_WAL_SENDER,
 	B_WAL_WRITER,
-	B_ARCHIVER,
-	B_LOGGER,
 } BackendType;
 
 extern PGDLLIMPORT BackendType MyBackendType;