merged

BitKeeper/etc/ignore:
  auto-union
BitKeeper/etc/logging_ok:
  auto-union
Docs/Support/texi2html:
  Auto merged
client/mysqltest.c:
  Auto merged
innobase/lock/lock0lock.c:
  Auto merged
innobase/row/row0sel.c:
  Auto merged
mysql-test/r/fulltext.result:
  Auto merged
mysql-test/r/heap.result:
  Auto merged
mysql-test/r/key.result:
  Auto merged
mysql-test/r/myisam.result:
  Auto merged
mysql-test/r/rpl000015.result:
  Auto merged
mysql-test/r/rpl_log_pos.result:
  Auto merged
mysql-test/r/rpl_rotate_logs.result:
  Auto merged
mysql-test/r/subselect.result:
  Auto merged
mysql-test/r/type_blob.result:
  Auto merged
mysql-test/t/key.test:
  Auto merged
mysql-test/t/myisam.test:
  Auto merged
mysql-test/t/rpl000015.test:
  Auto merged
mysql-test/t/rpl_log_pos.test:
  Auto merged
mysql-test/t/rpl_rotate_logs.test:
  Auto merged
mysql-test/t/subselect.test:
  Auto merged
sql/ha_ndbcluster.cc:
  Auto merged
sql/ha_ndbcluster.h:
  Auto merged
sql/handler.cc:
  Auto merged
sql/item.h:
  Auto merged
sql/item_cmpfunc.cc:
  Auto merged
sql/set_var.cc:
  Auto merged
sql/sql_do.cc:
  Auto merged
sql/sql_table.cc:
  Auto merged

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/item.h b/sql/item.h
index 9c036c28408..23515abc7a8 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -266,6 +266,14 @@ public:
   virtual bool get_time(TIME *ltime);
   virtual bool get_date_result(TIME *ltime,uint fuzzydate)
   { return get_date(ltime,fuzzydate); }
+  /*
+    This function is used only in Item_func_isnull/Item_func_isnotnull
+    (implementations of IS NULL/IS NOT NULL clauses). Item_func_is{not}null
+    calls this method instead of one of val/result*() methods, which
+    normally will set null_value. This allows to determine nullness of
+    a complex expression without fully evaluating it.
+    Any new item which can be NULL must implement this call.
+  */
   virtual bool is_null() { return 0; }
   /*
     it is "top level" item of WHERE clause and we do not need correct NULL
@@ -710,6 +718,8 @@ public:
   void print(String *str);
   /* parameter never equal to other parameter of other item */
   bool eq(const Item *item, bool binary_cmp) const { return 0; }
+  bool is_null()
+  { DBUG_ASSERT(state != NO_VALUE); return state == NULL_VALUE; }
 };
 
 class Item_int :public Item_num