Rename the "fast_promote" file to just "promote".

This keeps the usual trigger file name unchanged from 9.2, avoiding nasty
issues if you use a pre-9.3 pg_ctl binary with a 9.3 server or vice versa.
The fallback behavior of creating a full checkpoint before starting up is now
triggered by a file called "fallback_promote". That can be useful for
debugging purposes, but we don't expect any users to have to resort to that
and we might want to remove that in the future, which is why the fallback
mechanism is undocumented.

Author: hlinnaka

src/backend/access/transam/xlog.c

@@ -66,8 +66,8 @@ extern uint32 bootstrap_data_checksum_version;
 /* File path names (all relative to $PGDATA) */
 #define RECOVERY_COMMAND_FILE	"recovery.conf"
 #define RECOVERY_COMMAND_DONE	"recovery.done"
-#define PROMOTE_SIGNAL_FILE "promote"
-#define FAST_PROMOTE_SIGNAL_FILE "fast_promote"
+#define PROMOTE_SIGNAL_FILE		"promote"
+#define FALLBACK_PROMOTE_SIGNAL_FILE "fallback_promote"
 
 
 /* User-settable parameters */
@@ -11082,19 +11082,20 @@ CheckForStandbyTrigger(void)
 	{
 		/*
 		 * In 9.1 and 9.2 the postmaster unlinked the promote file inside the
-		 * signal handler. We now leave the file in place and let the Startup
-		 * process do the unlink. This allows Startup to know whether we're
-		 * doing fast or normal promotion. Fast promotion takes precedence.
+		 * signal handler. It now leaves the file in place and lets the
+		 * Startup process do the unlink. This allows Startup to know whether
+		 * it should create a full checkpoint before starting up (fallback
+		 * mode). Fast promotion takes precedence.
 		 */
-		if (stat(FAST_PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
+		if (stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
 		{
-			unlink(FAST_PROMOTE_SIGNAL_FILE);
 			unlink(PROMOTE_SIGNAL_FILE);
+			unlink(FALLBACK_PROMOTE_SIGNAL_FILE);
 			fast_promote = true;
 		}
-		else if (stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
+		else if (stat(FALLBACK_PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
 		{
-			unlink(PROMOTE_SIGNAL_FILE);
+			unlink(FALLBACK_PROMOTE_SIGNAL_FILE);
 			fast_promote = false;
 		}
 
@@ -11130,7 +11131,7 @@ CheckPromoteSignal(void)
 	struct stat stat_buf;
 
 	if (stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0 ||
-		stat(FAST_PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
+		stat(FALLBACK_PROMOTE_SIGNAL_FILE, &stat_buf) == 0)
 		return true;
 
 	return false;

src/bin/pg_ctl/pg_ctl.c

@@ -1099,12 +1099,11 @@ do_promote(void)
 	}
 
 	/*
-	 * For 9.3 onwards, use fast promotion as the default option. Promotion
+	 * For 9.3 onwards, "fast" promotion is performed. Promotion
 	 * with a full checkpoint is still possible by writing a file called
-	 * "promote", e.g. snprintf(promote_file, MAXPGPATH, "%s/promote",
-	 * pg_data);
+	 * "fallback_promote" instead of "promote"
 	 */
-	snprintf(promote_file, MAXPGPATH, "%s/fast_promote", pg_data);
+	snprintf(promote_file, MAXPGPATH, "%s/promote", pg_data);
 
 	if ((prmfile = fopen(promote_file, "w")) == NULL)
 	{