Bug#11766249 bug#59316: PARTITIONING AND INDEX_MERGE MEMORY LEAK

Update for previous patch according to reviewers comments.

Updated the constructors for ha_partitions to use the common
init_handler_variables functions

Added use of defines for size and offset to get better readability for the code that reads
and writes the .par file. Also refactored the get_from_handler_file function.

sql/ha_partition.h

@@ -55,6 +55,16 @@ typedef struct st_ha_data_partition
                                         HA_DUPLICATE_POS | \
                                         HA_CAN_SQL_HANDLER | \
                                         HA_CAN_INSERT_DELAYED)
+
+/* First 4 bytes in the .par file is the number of 32-bit words in the file */
+#define PAR_WORD_SIZE 4
+/* offset to the .par file checksum */
+#define PAR_CHECKSUM_OFFSET 4
+/* offset to the total number of partitions */
+#define PAR_NUM_PARTS_OFFSET 8
+/* offset to the engines array */
+#define PAR_ENGINES_OFFSET 12
+
 class ha_partition :public handler
 {
 private:
@@ -71,7 +81,7 @@ private:
   /* Data for the partition handler */
   int  m_mode;                          // Open mode
   uint m_open_test_lock;                // Open test_if_locked
-  char *m_file_buffer;                  // Buffer with names
+  char *m_file_buffer;                  // Content of the .par file 
   char *m_name_buffer_ptr;		// Pointer to first partition name
   plugin_ref *m_engine_array;           // Array of types of the handlers
   handler **m_file;                     // Array of references to handler inst.
@@ -281,7 +291,10 @@ private:
     And one method to read it in.
   */
   bool create_handler_file(const char *name);
-  bool get_from_handler_file(const char *name, MEM_ROOT *mem_root, bool clone);
+  bool setup_engine_array(MEM_ROOT *mem_root);
+  bool read_par_file(const char *name);
+  bool get_from_handler_file(const char *name, MEM_ROOT *mem_root,
+                             bool is_clone);
   bool new_handlers_from_part_info(MEM_ROOT *mem_root);
   bool create_handlers(MEM_ROOT *mem_root);
   void clear_handler_file();

sql/handler.cc

@@ -2045,14 +2045,21 @@ handler *handler::clone(const char *name, MEM_ROOT *mem_root)
     on this->table->mem_root and we will not be able to reclaim that memory 
     when the clone handler object is destroyed.
   */
-  if (!(new_handler->ref= (uchar*) alloc_root(mem_root, ALIGN_SIZE(ref_length)*2)))
-    return NULL;
-  if (new_handler && !new_handler->ha_open(table,
+  if (new_handler &&
+     !(new_handler->ref= (uchar*) alloc_root(mem_root,
+                                             ALIGN_SIZE(ref_length)*2)))
+    new_handler= NULL;
+  /*
+    TODO: Implement a more efficient way to have more than one index open for
+    the same table instance. The ha_open call is not cachable for clone.
+  */
+  if (new_handler && new_handler->ha_open(table,
                                           name,
                                           table->db_stat,
                                           HA_OPEN_IGNORE_IF_LOCKED))
+    new_handler= NULL;
+
   return new_handler;
-  return NULL;
 }