merge with 5.3

sql/sql_insert.cc:
  CREATE ... IF NOT EXISTS may do nothing, but
  it is still not a failure. don't forget to my_ok it.
  ******
  CREATE ... IF NOT EXISTS may do nothing, but
  it is still not a failure. don't forget to my_ok it.
sql/sql_table.cc:
  small cleanup
  ******
  small cleanup

1 files changed, 10 insertions, 0 deletions

diff --git a/include/my_tree.h b/include/my_tree.h
index b4f2c07c794..3524c82a2bc 100644
--- a/include/my_tree.h
+++ b/include/my_tree.h
@@ -31,7 +31,17 @@ extern "C" {
 
 #define tree_set_pointer(element,ptr) *((uchar **) (element+1))=((uchar*) (ptr))
 
+/*
+  A tree with its flag set to TREE_ONLY_DUPS behaves differently on inserting 
+  an element that is not in the tree:
+  the element is not added at all, but instead tree_insert() returns a special
+  address TREE_ELEMENT_UNIQUE as an indication that the function has not failed
+  due to lack of memory. 
+*/
+
+#define TREE_ELEMENT_UNIQUE ((TREE_ELEMENT *) 1)
 #define TREE_NO_DUPS 1
+#define TREE_ONLY_DUPS 2
 
 typedef enum { left_root_right, right_root_left } TREE_WALK;
 typedef uint32 element_count;