bk commit into 5.1 tree (stewart:1.1830)

[Stewart Smith]

Below is the list of changes that have just been committed into a local
5.1 repository of stewart. When stewart does a push these changes will
be propagated to the main repository and, within 24 hours after the
push, to the public repository.
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see http://dev.mysql.com/doc/mysql/en/installing-source-tree.html

ChangeSet
  1.1830 05/05/09 09:59:08 stewart@stripped +1 -0
  Optimise bitvector to avoid malloc
  
  (profiling showed that this can make a speed improvement for ndb injector thread)

  sql/bitvector.h
    1.2 05/05/09 09:59:00 stewart@stripped +8 -2
    Avoid a malloc on the common case (where common case= using it for fields in NDB tables)

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	stewart
# Host:	kennedy.(none)
# Root:	/home/stewart/Documents/MySQL/5.1/wl2325

--- 1.1/sql/bitvector.h	2005-04-26 12:20:01 +02:00
+++ 1.2/sql/bitvector.h	2005-05-09 09:59:00 +02:00
@@ -135,8 +135,13 @@
   }
 
   explicit bitvector(size_t size, bool value= false) 
-    : m_size(size), m_data(my_malloc(byte_size(size), MYF(0)))
+    : m_size(size)
   {
+    if(byte_size(size)<=sizeof(smalldata))
+      m_data= smalldata;
+    else
+      m_data= my_malloc(byte_size(size), MYF(0));
+
     if (value)
       set_all();
     else
@@ -171,7 +176,7 @@
 
   ~bitvector() 
   {
-    if (m_data)
+    if (m_data && m_data!=smalldata)
       my_free(m_data, MYF(0));
   }
 
@@ -249,6 +254,7 @@
 private:
   size_t m_size;
   byte *m_data;
+  byte smalldata[16];
 };
 
 #endif /* BITVECTOR_H */