1 files changed, 47 insertions, 11 deletions

diff --git a/include/heap.h b/include/heap.h
index 63f2abbabc7..ac2b38d1f2d 100644
--- a/include/heap.h
+++ b/include/heap.h
@@ -63,18 +63,48 @@ typedef struct st_heap_ptrs
 
 struct st_level_info
 {
-  uint free_ptrs_in_block,records_under_level;
-  HP_PTRS *last_blocks;			/* pointers to HP_PTRS or records */
+  /* Number of unused slots in *last_blocks HP_PTRS block (0 for 0th level) */
+  uint free_ptrs_in_block;
+  
+  /*
+    Maximum number of records that can be 'contained' inside of each element
+    of last_blocks array. For level 0 - 1, for level 1 - HP_PTRS_IN_NOD, for 
+    level 2 - HP_PTRS_IN_NOD^2 and so forth.
+  */
+  uint records_under_level;
+
+  /*
+    Ptr to last allocated HP_PTRS (or records buffer for level 0) on this 
+    level.
+  */
+  HP_PTRS *last_blocks;			
 };
 
-typedef struct st_heap_block		/* The data is saved in blocks */
+
+/*
+  Heap table records and hash index entries are stored in HP_BLOCKs.
+  HP_BLOCK is used as a 'growable array' of fixed-size records. Size of record
+  is recbuffer bytes.
+  The internal representation is as follows:
+  HP_BLOCK is a hierarchical structure of 'blocks'.
+  A block at level 0 is an array records_in_block records. 
+  A block at higher level is an HP_PTRS structure with pointers to blocks at 
+  lower levels.
+  At the highest level there is one top block. It is stored in HP_BLOCK::root.
+
+  See hp_find_block for a description of how record pointer is obtained from 
+  its index.
+  See hp_get_new_block 
+*/
+
+typedef struct st_heap_block
 {
-  HP_PTRS *root;
+  HP_PTRS *root;                        /* Top-level block */ 
   struct st_level_info level_info[HP_MAX_LEVELS+1];
-  uint levels;
-  uint records_in_block;		/* Records in a heap-block */
+  uint levels;                          /* number of used levels */
+  uint records_in_block;		/* Records in one heap-block */
   uint recbuffer;			/* Length of one saved record */
-  ulong last_allocated;			/* Blocks allocated, used by keys */
+  ulong last_allocated; /* number of records there is allocated space for */
 } HP_BLOCK;
 
 struct st_heap_info;			/* For referense */
@@ -87,11 +117,16 @@ typedef struct st_hp_keydef		/* Key definition with open */
   uint8 algorithm;			/* HASH / BTREE */
   HA_KEYSEG *seg;
   HP_BLOCK block;			/* Where keys are saved */
+  /*
+    Number of buckets used in hash table. Used only to provide
+    #records estimates for heap key scans.
+  */
+  ha_rows hash_buckets; 
   TREE rb_tree;
   int (*write_key)(struct st_heap_info *info, struct st_hp_keydef *keyinfo,
 		   const byte *record, byte *recpos);
-  int (*delete_key)(struct st_heap_info *info, struct st_hp_keydef *keyinfo, 
-  		   const byte *record, byte *recpos, int flag);
+  int (*delete_key)(struct st_heap_info *info, struct st_hp_keydef *keyinfo,
+		   const byte *record, byte *recpos, int flag);
   uint (*get_key_length)(struct st_hp_keydef *keydef, const byte *key);
 } HP_KEYDEF;
 
@@ -100,9 +135,9 @@ typedef struct st_heap_share
   HP_BLOCK block;
   HP_KEYDEF  *keydef;
   ulong min_records,max_records;	/* Params to open */
-  ulong data_length,index_length;
+  ulong data_length,index_length,max_table_size;
   uint records;				/* records */
-  uint blength;
+  uint blength;				/* records rounded up to 2^n */
   uint deleted;				/* Deleted records in database */
   uint reclength;			/* Length of one record */
   uint changed;
@@ -150,6 +185,7 @@ typedef struct st_heap_create_info
 {
   uint auto_key;
   uint auto_key_type;
+  ulong max_table_size;
   ulonglong auto_increment;
 } HP_CREATE_INFO;