BUG#19501: Data_Free incorrectly handled for partitioned tables

mysql-test/r/partition.result

@@ -886,4 +886,18 @@ s1
 2
 3
 drop table t1;
+CREATE TABLE t1 (a int) ENGINE = MYISAM PARTITION BY KEY(a);
+INSERT into t1 values (1), (2);
+SHOW TABLE STATUS;
+Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
+t1	MyISAM	10	Fixed	2	7	14	0	0	0	NULL	NULL	NULL	NULL	latin1_swedish_ci	NULL	partitioned	
+DELETE from t1 where a = 1;
+SHOW TABLE STATUS;
+Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
+t1	MyISAM	10	Fixed	1	14	14	0	0	7	NULL	NULL	NULL	NULL	latin1_swedish_ci	NULL	partitioned	
+ALTER TABLE t1 OPTIMIZE PARTITION p0;
+SHOW TABLE STATUS;
+Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
+t1	MyISAM	10	Fixed	1	7	7	0	1024	0	NULL	NULL	NULL	NULL	latin1_swedish_ci	NULL	partitioned	
+DROP TABLE t1;
 End of 5.1 tests

mysql-test/t/partition.test

@@ -1009,4 +1009,19 @@ select auto_increment from information_schema.tables where table_name='t1';
 select * from t1;
 drop table t1;
 
+#
+# BUG 19501 Partitions: SHOW TABLE STATUS shows wrong Data_free
+#
+CREATE TABLE t1 (a int) ENGINE = MYISAM PARTITION BY KEY(a);
+INSERT into t1 values (1), (2);
+--replace_column 9 0 12 NULL 13 NULL 14 NULL
+SHOW TABLE STATUS;
+DELETE from t1 where a = 1;
+--replace_column 9 0 12 NULL 13 NULL 14 NULL
+SHOW TABLE STATUS;
+ALTER TABLE t1 OPTIMIZE PARTITION p0;
+--replace_column 12 NULL 13 NULL 14 NULL
+SHOW TABLE STATUS;
+DROP TABLE t1;
+
 --echo End of 5.1 tests

sql/ha_partition.cc

@@ -4169,6 +4169,8 @@ void ha_partition::info(uint flag)
       index_file_length: Length of index file, in principle bytes in
       indexes in the table
       We report sum
+      delete_length: Length of free space easily used by new records in table
+      We report sum
       mean_record_length:Mean record length in the table
       We calculate this
       check_time:        Time of last check (only applicable to MyISAM)
@@ -4178,6 +4180,7 @@ void ha_partition::info(uint flag)
     deleted= 0;
     data_file_length= 0;
     index_file_length= 0;
+    delete_length= 0;
     check_time= 0;
     file_array= m_file;
     do
@@ -4190,6 +4193,7 @@ void ha_partition::info(uint flag)
         deleted+= file->deleted;
         data_file_length+= file->data_file_length;
         index_file_length+= file->index_file_length;
+        delete_length+= file->delete_length;
         if (file->check_time > check_time)
           check_time= file->check_time;
       }