Make pg_basebackup work with pre-9.3 servers, and add server version check.

A new 'starttli' field was added to the response of BASE_BACKUP command.
Make pg_basebackup tolerate the case that it's missing, so that it still
works with older servers.

Add an explicit check for the server version, so that you get a nicer error
message if you try to use it with a pre-9.1 server.

The streaming protocol message format changed in 9.3, so -X stream still won't
work with pre-9.3 servers. I added a version check to ReceiveXLogStream()
earlier, but write that slightly differently, so that in 9.4, it will still
work with a 9.3 server. (In 9.4, the error message needs to be adjusted to
"9.3 or above", though). Also, if the version check fails, don't retry.

1 files changed, 39 insertions, 3 deletions

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index eacb5922a2a..45585069a5e 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -1223,12 +1223,16 @@ BaseBackup(void)
 {
 	PGresult   *res;
 	char	   *sysidentifier;
+	uint32		latesttli;
 	uint32		starttli;
 	char		current_path[MAXPGPATH];
 	char		escaped_label[MAXPGPATH];
 	int			i;
 	char		xlogstart[64];
 	char		xlogend[64];
+	int			minServerMajor,
+				maxServerMajor;
+	int			serverMajor;
 
 	/*
 	 * Connect in replication mode to the server
@@ -1239,6 +1243,31 @@ BaseBackup(void)
 		exit(1);
 
 	/*
+	 * Check server version. BASE_BACKUP command was introduced in 9.1, so
+	 * we can't work with servers older than 9.1.
+	 */
+	minServerMajor = 901;
+	maxServerMajor = PG_VERSION_NUM / 100;
+	serverMajor = PQserverVersion(conn) / 100;
+	if (serverMajor < minServerMajor || serverMajor > maxServerMajor)
+	{
+		const char *serverver = PQparameterStatus(conn, "server_version");
+		fprintf(stderr, _("%s: incompatible server version %s\n"),
+				progname, serverver ? serverver : "'unknown'");
+		disconnect_and_exit(1);
+	}
+
+	/*
+	 * If WAL streaming was requested, also check that the server is new
+	 * enough for that.
+	 */
+	if (streamwal && !CheckServerVersionForStreaming(conn))
+	{
+		/* Error message already written in CheckServerVersionForStreaming() */
+		disconnect_and_exit(1);
+	}
+
+	/*
 	 * Build contents of recovery.conf if requested
 	 */
 	if (writerecoveryconf)
@@ -1262,6 +1291,7 @@ BaseBackup(void)
 		disconnect_and_exit(1);
 	}
 	sysidentifier = pg_strdup(PQgetvalue(res, 0, 0));
+	latesttli = atoi(PQgetvalue(res, 0, 1));
 	PQclear(res);
 
 	/*
@@ -1293,7 +1323,7 @@ BaseBackup(void)
 				progname, PQerrorMessage(conn));
 		disconnect_and_exit(1);
 	}
-	if (PQntuples(res) != 1 || PQnfields(res) < 2)
+	if (PQntuples(res) != 1)
 	{
 		fprintf(stderr,
 				_("%s: server returned unexpected response to BASE_BACKUP command; got %d rows and %d fields, expected %d rows and %d fields\n"),
@@ -1302,8 +1332,14 @@ BaseBackup(void)
 	}
 
 	strcpy(xlogstart, PQgetvalue(res, 0, 0));
-	starttli = atoi(PQgetvalue(res, 0, 1));
-
+	/*
+	 * 9.3 and later sends the TLI of the starting point. With older servers,
+	 * assume it's the same as the latest timeline reported by IDENTIFY_SYSTEM.
+	 */
+	if (PQnfields(res) >= 2)
+		starttli = atoi(PQgetvalue(res, 0, 1));
+	else
+		starttli = latesttli;
 	PQclear(res);
 	MemSet(xlogend, 0, sizeof(xlogend));