MWL#121-125 DS-MRR improvements

- Address Monty's review feedback, portion 3

sql/multi_range_read.cc

@@ -414,8 +414,6 @@ void Mrr_ordered_index_reader::resume_read()
 int Mrr_ordered_index_reader::refill_buffer(bool initial)
 {
   KEY_MULTI_RANGE cur_range;
-  uchar **range_info_ptr= (uchar**)&cur_range.ptr;
-  uchar *key_ptr;
   DBUG_ENTER("Mrr_ordered_index_reader::refill_buffer");
 
   DBUG_ASSERT(key_buffer->is_empty());
@@ -425,9 +423,8 @@ int Mrr_ordered_index_reader::refill_buffer(bool initial)
 
   buf_manager->reset_buffer_sizes(buf_manager->arg);
   key_buffer->reset();
-  key_buffer->setup_writing(&key_ptr, keypar.key_size_in_keybuf,
+  key_buffer->setup_writing(keypar.key_size_in_keybuf,
-                            is_mrr_assoc? (uchar**)&range_info_ptr : NULL,
+                            is_mrr_assoc? sizeof(char*) : 0);
-                            is_mrr_assoc? sizeof(uchar*):0);
 
   while (key_buffer->can_write() && 
          !(source_exhausted= mrr_funcs.next(mrr_iter, &cur_range)))
@@ -435,9 +432,10 @@ int Mrr_ordered_index_reader::refill_buffer(bool initial)
     DBUG_ASSERT(cur_range.range_flag & EQ_RANGE);
 
     /* Put key, or {key, range_id} pair into the buffer */
-    key_ptr= (keypar.use_key_pointers)? (uchar*)&cur_range.start_key.key : 
+    key_buffer->write_ptr1= keypar.use_key_pointers ?
-                                        (uchar*)cur_range.start_key.key;
+                              (uchar*)&cur_range.start_key.key : 
-
+                              (uchar*)cur_range.start_key.key;
+    key_buffer->write_ptr2= (uchar*)&cur_range.ptr;
     key_buffer->write();
   }
   
@@ -591,16 +589,14 @@ void Mrr_index_reader::position()
 int Mrr_ordered_rndpos_reader::refill_from_index_reader()
 {
   char *range_info;
-  uchar **range_info_ptr= (uchar**)&range_info;
   int res;
   DBUG_ENTER("Mrr_ordered_rndpos_reader::refill_from_index_reader");
 
   DBUG_ASSERT(rowid_buffer->is_empty());
   index_rowid= index_reader->get_rowid_ptr();
   rowid_buffer->reset();
-  rowid_buffer->setup_writing(&index_rowid, file->ref_length,
+  rowid_buffer->setup_writing(file->ref_length,
-                              is_mrr_assoc? (uchar**)&range_info_ptr: NULL,
+                              is_mrr_assoc? sizeof(char*) : 0);
-                              is_mrr_assoc? sizeof(char*):0);
 
   last_identical_rowid= NULL;
 
@@ -620,6 +616,8 @@ int Mrr_ordered_rndpos_reader::refill_from_index_reader()
     index_reader->position();
 
     /* Put rowid, or {rowid, range_id} pair into the buffer */
+    rowid_buffer->write_ptr1= index_rowid;
+    rowid_buffer->write_ptr2= (uchar*)&range_info;
     rowid_buffer->write();
   }
    

sql/sql_lifo_buffer.h

@@ -28,18 +28,18 @@ class Backward_lifo_buffer;
 class Lifo_buffer 
 {
 protected:
-  /**
-    Pointers to data to be written. write() call will assume that 
-    (*write_ptr1) points to size1 bytes of data to be written.
-    If write_ptr2 != NULL then the buffer stores pairs, and (*write_ptr2) 
-    points to size2 bytes of data that form the second component.
-  */
-  uchar **write_ptr1;
   size_t size1;
-  uchar **write_ptr2;
   size_t size2;
 
 public:
+  /**
+    write() will put into buffer size1 bytes pointed by write_ptr1. If
+    size2!=0, then they will be accompanied by size2 bytes pointed by
+    write_ptr2.
+  */
+  uchar *write_ptr1;
+  uchar *write_ptr2;
+
   /**
     read() will do reading by storing pointers to read data into read_ptr1 or
     into (read_ptr1, read_ptr2), depending on whether the buffer was set to
@@ -75,11 +75,9 @@ public:
     Specify where write() should get the source data from, as well as source
     data size.
   */
-  void setup_writing(uchar **data1, size_t len1, uchar **data2, size_t len2)
+  void setup_writing(size_t len1, size_t len2)
   {
-    write_ptr1= data1;
     size1= len1;
-    write_ptr2= data2;
     size2= len2;
   }
 
@@ -95,7 +93,7 @@ public:
   
   bool can_write()
   {
-    return have_space_for(size1 + (write_ptr2 ? size2 : 0));
+    return have_space_for(size1 + size2);
   }
   virtual void write() = 0;
 
@@ -104,7 +102,7 @@ public:
   
   void sort(qsort2_cmp cmp_func, void *cmp_func_arg)
   {
-    uint elem_size= size1 + (write_ptr2 ? size2 : 0);
+    uint elem_size= size1 + size2;
     uint n_elements= used_size() / elem_size;
     my_qsort2(used_area(), n_elements, elem_size, cmp_func, cmp_func_arg);
   }
@@ -164,9 +162,9 @@ public:
 
   void write()
   {
-    write_bytes(*write_ptr1, size1);
+    write_bytes(write_ptr1, size1);
-    if (write_ptr2)
+    if (size2)
-      write_bytes(*write_ptr2, size2);
+      write_bytes(write_ptr2, size2);
   }
   void write_bytes(const uchar *data, size_t bytes)
   {
@@ -257,8 +255,8 @@ public:
   void write()
   {
     if (write_ptr2)
-      write_bytes(*write_ptr2, size2);
+      write_bytes(write_ptr2, size2);
-    write_bytes(*write_ptr1, size1);
+    write_bytes(write_ptr1, size1);
   }
   void write_bytes(const uchar *data, size_t bytes)
   {