Fixed bug with UPDATE/DELETE on UNIQUE key which could be NULL

Docs/manual.texi:
  Updated replication section
mysql-test/r/null_key.result:
  Added test UPDATE/DELETE with IS NULL on unique key
mysql-test/t/null_key.test:
  Added test UPDATE/DELETE with IS NULL on unique key
mysys/Makefile.am:
  Removed -f from $CP as this is not portable
  Fixed rule for testhash
sql/field.cc:
  Safety fix
sql/opt_range.cc:
  Fixed bug with UPDATE/DELETE on UNIQUE key which could be NULL
sql/opt_range.h:
  Fixed bug with UPDATE/DELETE on UNIQUE key which could be NULL

3 files changed, 31 insertions, 4 deletions

diff --git a/sql/field.cc b/sql/field.cc
index f2310dd0229..f7dbd3c72f0 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -3891,7 +3891,7 @@ String *Field_blob::val_str(String *val_buffer __attribute__((unused)),
   char *blob;
   memcpy_fixed(&blob,ptr+packlength,sizeof(char*));
   if (!blob)
-    val_ptr->length(0);
+    val_ptr->set("",0);				// A bit safer than ->length(0)
   else
     val_ptr->set((const char*) blob,get_length(ptr));
   return val_ptr;
diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index 4c1a0db72b7..eedae87719d 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -321,7 +321,7 @@ static bool get_quick_keys(PARAM *param,QUICK_SELECT *quick,KEY_PART *key,
 static bool eq_tree(SEL_ARG* a,SEL_ARG *b);
 
 static SEL_ARG null_element(SEL_ARG::IMPOSSIBLE);
-
+static bool null_part_in_key(KEY_PART *key_part, const char *key, uint length);
 
 /***************************************************************************
 ** Basic functions for SQL_SELECT and QUICK_SELECT
@@ -2306,7 +2306,15 @@ get_quick_keys(PARAM *param,QUICK_SELECT *quick,KEY_PART *key,
       KEY *table_key=quick->head->key_info+quick->index;
       flag=EQ_RANGE;
       if (table_key->flags & HA_NOSAME && key->part == table_key->key_parts-1)
-	flag|= UNIQUE_RANGE;
+      {
+	if (!(table_key->flags & HA_NULL_PART_KEY) ||
+	    !null_part_in_key(key,
+			      param->min_key,
+			      (uint) (tmp_min_key - param->min_key)))
+	  flag|= UNIQUE_RANGE;
+	else
+	  flag|= NULL_RANGE;
+      }
     }
   }
 
@@ -2339,7 +2347,7 @@ bool QUICK_SELECT::unique_key_range()
   if (ranges.elements == 1)
   {
     QUICK_RANGE *tmp;
-    if ((tmp=ranges.head())->flag & EQ_RANGE)
+    if (((tmp=ranges.head())->flag & (EQ_RANGE | NULL_RANGE)) == EQ_RANGE)
     {
       KEY *key=head->key_info+index;
       return ((key->flags & HA_NOSAME) &&
@@ -2349,6 +2357,24 @@ bool QUICK_SELECT::unique_key_range()
   return 0;
 }
 
+
+/* Returns true if any part of the key is NULL */
+
+static bool null_part_in_key(KEY_PART *key_part, const char *key, uint length)
+{
+  for (const char *end=key+length ; 
+       key < end;
+       key+= key_part++->part_length)
+  {
+    if (key_part->null_bit)
+    {
+      if (*key++)
+	return 1;
+    }
+  }
+  return 0;
+}
+
 /****************************************************************************
 ** Create a QUICK RANGE based on a key
 ****************************************************************************/
diff --git a/sql/opt_range.h b/sql/opt_range.h
index 2005773eca7..247dd260817 100644
--- a/sql/opt_range.h
+++ b/sql/opt_range.h
@@ -30,6 +30,7 @@
 #define NEAR_MAX	8
 #define UNIQUE_RANGE	16
 #define EQ_RANGE	32
+#define NULL_RANGE	64
 
 typedef struct st_key_part {
   uint16 key,part,part_length;