branches/5.1: Fix bug#29507 TRUNCATE shows to many rows effected

In InnoDB, the row count is only a rough estimate used by SQL
optimization. InnoDB is now return row count 0 for TRUNCATE operation.

handler/ha_innodb.cc

@@ -5782,6 +5782,13 @@ ha_innobase::info(
 			n_rows++;
 		}
 
+		/* Fix bug#29507: TRUNCATE shows too many rows affected.
+		Do not show the estimates for TRUNCATE command. */
+		if (thd_sql_command(user_thd) == SQLCOM_TRUNCATE) {
+
+			n_rows = 0;
+		}
+
 		stats.records = (ha_rows)n_rows;
 		stats.deleted = 0;
 		stats.data_file_length = ((ulonglong)

mysql-test/innodb.result

@@ -3264,3 +3264,14 @@ AUTO_INCREMENT
 200
 DROP TABLE t2;
 DROP TABLE t1;
+CREATE TABLE t1 (c1 int default NULL,
+c2 int default NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+TRUNCATE TABLE t1;
+affected rows: 0
+INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3), (4, 4), (5, 5);
+affected rows: 5
+info: Records: 5  Duplicates: 0  Warnings: 0
+TRUNCATE TABLE t1;
+affected rows: 0
+DROP TABLE t1;

mysql-test/innodb.test

@@ -2458,7 +2458,22 @@ SELECT AUTO_INCREMENT FROM INFORMATION_SCHEMA.TABLES WHERE table_name = 't2';
 DROP TABLE t2;
 DROP TABLE t1;
 # End 34920 test
+# Bug #29507 TRUNCATE shows to many rows effected
+#
+CONNECTION default;
+CREATE TABLE t1 (c1 int default NULL,
+		 c2 int default NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+
+--enable_info
+TRUNCATE TABLE t1;
 
+INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3), (4, 4), (5, 5);
+TRUNCATE TABLE t1;
+
+--disable_info
+DROP TABLE t1;
+#
 #######################################################################
 #                                                                     #
 # Please, DO NOT TOUCH this file as well as the innodb.result file.   #