pg_upgrade: Fix problems caused by renaming pg_resetxlog.

Commit 85c11324 renamed pg_resetxlog
to pg_resetwal, but didn't make pg_upgrade smart enough to cope with
the situation.

Michael Paquier, per a complaint from Jeff Janes

src/bin/pg_upgrade/check.c

@@ -26,7 +26,6 @@ static void check_for_isn_and_int8_passing_mismatch(ClusterInfo *cluster);
 static void check_for_reg_data_type_usage(ClusterInfo *cluster);
 static void check_for_jsonb_9_4_usage(ClusterInfo *cluster);
 static void check_for_pg_role_prefix(ClusterInfo *cluster);
-static void get_bin_version(ClusterInfo *cluster);
 static char *get_canonical_locale_name(int category, const char *locale);
 
 
@@ -241,10 +240,6 @@ check_cluster_versions(void)
 	if (old_cluster.major_version > new_cluster.major_version)
 		pg_fatal("This utility cannot be used to downgrade to older major PostgreSQL versions.\n");
 
-	/* get old and new binary versions */
-	get_bin_version(&old_cluster);
-	get_bin_version(&new_cluster);
-
 	/* Ensure binaries match the designated data directories */
 	if (GET_MAJOR_VERSION(old_cluster.major_version) !=
 		GET_MAJOR_VERSION(old_cluster.bin_version))
@@ -1080,34 +1075,6 @@ check_for_pg_role_prefix(ClusterInfo *cluster)
 	check_ok();
 }
 
-static void
-get_bin_version(ClusterInfo *cluster)
-{
-	char		cmd[MAXPGPATH],
-				cmd_output[MAX_STRING];
-	FILE	   *output;
-	int			pre_dot = 0,
-				post_dot = 0;
-
-	snprintf(cmd, sizeof(cmd), "\"%s/pg_ctl\" --version", cluster->bindir);
-
-	if ((output = popen(cmd, "r")) == NULL ||
-		fgets(cmd_output, sizeof(cmd_output), output) == NULL)
-		pg_fatal("could not get pg_ctl version data using %s: %s\n",
-				 cmd, strerror(errno));
-
-	pclose(output);
-
-	/* Remove trailing newline */
-	if (strchr(cmd_output, '\n') != NULL)
-		*strchr(cmd_output, '\n') = '\0';
-
-	if (sscanf(cmd_output, "%*s %*s %d.%d", &pre_dot, &post_dot) < 1)
-		pg_fatal("could not get version from %s\n", cmd);
-
-	cluster->bin_version = (pre_dot * 100 + post_dot) * 100;
-}
-
 
 /*
  * get_canonical_locale_name

src/bin/pg_upgrade/controldata.c

@@ -70,6 +70,7 @@ get_control_data(ClusterInfo *cluster, bool live_check)
 	uint32		tli = 0;
 	uint32		logid = 0;
 	uint32		segno = 0;
+	char	   *resetwal_bin;
 
 
 	/*
@@ -111,9 +112,14 @@ get_control_data(ClusterInfo *cluster, bool live_check)
 	pg_putenv("LC_ALL", NULL);
 	pg_putenv("LC_MESSAGES", "C");
 
+	/* pg_resetxlog has been renamed to pg_resetwal in version 10 */
+	if (GET_MAJOR_VERSION(cluster->bin_version) < 1000)
+		resetwal_bin = "pg_resetxlog\" -n";
+	else
+		resetwal_bin = "pg_resetwal\" -n";
 	snprintf(cmd, sizeof(cmd), "\"%s/%s \"%s\"",
 			 cluster->bindir,
-			 live_check ? "pg_controldata\"" : "pg_resetwal\" -n",
+			 live_check ? "pg_controldata\"" : resetwal_bin,
 			 cluster->pgdata);
 	fflush(stdout);
 	fflush(stderr);

src/bin/pg_upgrade/exec.c

@@ -16,6 +16,7 @@
 
 static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster);
+static void get_bin_version(ClusterInfo *cluster);
 static void validate_exec(const char *dir, const char *cmdName);
 
 #ifdef WIN32
@@ -23,6 +24,40 @@ static int	win32_check_directory_write_permissions(void);
 #endif
 
 
+/*
+ * get_bin_version
+ *
+ *	Fetch versions of binaries for cluster.
+ */
+static void
+get_bin_version(ClusterInfo *cluster)
+{
+	char		cmd[MAXPGPATH],
+				cmd_output[MAX_STRING];
+	FILE	   *output;
+	int			pre_dot = 0,
+				post_dot = 0;
+
+	snprintf(cmd, sizeof(cmd), "\"%s/pg_ctl\" --version", cluster->bindir);
+
+	if ((output = popen(cmd, "r")) == NULL ||
+		fgets(cmd_output, sizeof(cmd_output), output) == NULL)
+		pg_fatal("could not get pg_ctl version data using %s: %s\n",
+				 cmd, strerror(errno));
+
+	pclose(output);
+
+	/* Remove trailing newline */
+	if (strchr(cmd_output, '\n') != NULL)
+		*strchr(cmd_output, '\n') = '\0';
+
+	if (sscanf(cmd_output, "%*s %*s %d.%d", &pre_dot, &post_dot) < 1)
+		pg_fatal("could not get version from %s\n", cmd);
+
+	cluster->bin_version = (pre_dot * 100 + post_dot) * 100;
+}
+
+
 /*
  * exec_prog()
  *		Execute an external program with stdout/stderr redirected, and report
@@ -335,6 +370,19 @@ check_bin_dir(ClusterInfo *cluster)
 
 	validate_exec(cluster->bindir, "postgres");
 	validate_exec(cluster->bindir, "pg_ctl");
+
+	/*
+	 * Fetch the binary versions after checking for the existence of pg_ctl,
+	 * this gives a correct error if the binary used itself for the version
+	 * fetching is broken.
+	 */
+	get_bin_version(&old_cluster);
+	get_bin_version(&new_cluster);
+
+	/* pg_resetxlog has been renamed to pg_resetwal in version 10 */
+	if (GET_MAJOR_VERSION(cluster->bin_version) < 1000)
+		validate_exec(cluster->bindir, "pg_resetxlog");
+	else
 		validate_exec(cluster->bindir, "pg_resetwal");
 	if (cluster == &new_cluster)
 	{