option to free_root() to not my_free() the blocks

fixed bug/updated count_distinct2 test
changed reset in count distinct to avoid calls to my_free()

2 files changed, 55 insertions, 4 deletions

diff --git a/mysys/my_alloc.c b/mysys/my_alloc.c
index db482454e69..b82ff965dfb 100644
--- a/mysys/my_alloc.c
+++ b/mysys/my_alloc.c
@@ -100,7 +100,41 @@ gptr alloc_root(MEM_ROOT *mem_root,unsigned int Size)
 #endif
 }
 
-	/* deallocate everything used by alloc_root */
+static inline void mark_blocks_free(MEM_ROOT* root)
+{
+  reg1 USED_MEM *next,*last = 0;
+
+  /* iterate through (partially) free blocks, mark them fully free */
+  for(next = root->free; next; next = next->next )
+    {
+      last = next;
+      next->left = next->size - ALIGN_SIZE(sizeof(USED_MEM));
+    }
+  /* if free block list was not empty, point the next of the
+     last free block to the beginning of the used list  */
+  next = root->used; /* a little optimization to avoid dereferencing root
+		      twice - we will shortly start iterating through used
+		      list */
+  if(last)
+    last->next = next;
+  else /* if free list is empty, just point it to the current used*/
+    root->free = next;
+
+  /* now go through the current used list, and mark each block
+     as fully free. Note that because of our optimization, we do not
+     need to initialize next here - see above
+  */
+  for(;next; next = next->next)
+      next->left = next->size - ALIGN_SIZE(sizeof(USED_MEM));
+
+  /* Now everything is set - we just need to indicate that nothing is used
+     anymore
+  */
+  root->used = 0;
+}
+
+	/* deallocate everything used by alloc_root or just move
+	 used blocks to free list if called with MY_USED_TO_FREE */
 
 void free_root(MEM_ROOT *root, myf MyFlags)
 {
@@ -109,6 +143,11 @@ void free_root(MEM_ROOT *root, myf MyFlags)
 
   if (!root)
     DBUG_VOID_RETURN; /* purecov: inspected */
+  if(MyFlags & MY_MARK_BLOCKS_FREE)
+    {
+      mark_blocks_free(root);
+      DBUG_VOID_RETURN;
+    }
   if (!(MyFlags & MY_KEEP_PREALLOC))
     root->pre_alloc=0;
 
diff --git a/mysys/tree.c b/mysys/tree.c
index e46ff00adad..af64be55d2f 100644
--- a/mysys/tree.c
+++ b/mysys/tree.c
@@ -103,9 +103,9 @@ void init_tree(TREE *tree, uint default_alloc_size, int size,
   DBUG_VOID_RETURN;
 }
 
-void delete_tree(TREE *tree)
+static void free_tree(TREE *tree, myf free_flags)
 {
-  DBUG_ENTER("delete_tree");
+  DBUG_ENTER("free_tree");
   DBUG_PRINT("enter",("tree: %lx",tree));
 
   if (tree->root)				/* If initialized */
@@ -116,7 +116,7 @@ void delete_tree(TREE *tree)
     {
       if (tree->free)
 	delete_tree_element(tree,tree->root);
-      free_root(&tree->mem_root,MYF(0));
+      free_root(&tree->mem_root, free_flags);
     }
   }
   tree->root= &tree->null_element;
@@ -125,6 +125,18 @@ void delete_tree(TREE *tree)
   DBUG_VOID_RETURN;
 }
 
+void delete_tree(TREE* tree)
+{
+  free_tree(tree, MYF(0)); /* my_free() mem_root if applicable */
+}
+
+void reset_tree(TREE* tree)
+{
+  free_tree(tree, MYF(MY_MARK_BLOCKS_FREE));
+  /* do not my_free() mem_root if applicable, just mark blocks as free */
+}
+
+
 static void delete_tree_element(TREE *tree, TREE_ELEMENT *element)
 {
   if (element != &tree->null_element)