bk commit into 4.1 tree (gkodinov:1.2459) BUG#18492

[kgeorge]

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ChangeSet
  1.2459 06/04/26 10:37:29 gkodinov@stripped +3 -0
  BUG#18492: mysqld reports ER_ILLEGAL_REFERENCE in --ps-protocol
  
  In the code that converts IN predicates to EXISTS predicates it is changing
  the select list elements to constant 1. Example :
  
  SELECT ... FROM ... WHERE a IN (SELECT c FROM ...)
  
  is transformed to :
  
  SELECT ... FROM ... WHERE EXISTS (SELECT 1 FROM ... HAVING a = c)
  
  However there can no FROM clause in the IN subquery and it may not be a
  simple select :
  
  SELECT ... FROM ... WHERE a IN (SELECT f(..) AS c UNION SELECT ...)
  
  This query is transformed to :
  
   SELECT ... FROM ... WHERE
     EXISTS (SELECT 1 FROM (SELECT f(..) AS c UNION SELECT ...) x HAVING a = c)
  
  In the above query the c in the HAVING clause is made to be an Item_null_helper
  (a subclass of Item_ref) pointing to the real Item_field (witch is not
  referenced anywhere else in the query anymore). This is done because
  Item_ref_null_helper collects information whether there are NULL values in
  the result.
  This is OK for directly executed statements, because the Item_field pointed
  by the Item_null_helper is already fixed when the transformation is done.
  But when executed as a prepared statement all the Item instances are
  "un-fixed" before the recompilation of the prepared statement. So when the
  Item_null_helper gets fixed it discovers that the Item_field it points to
  is not fixed and issues an error.
  
  The remedy is to keep the original select list references when there are
  no tables in the FROM clause. So the above becomes :
  
   SELECT ... FROM ... WHERE
     EXISTS (SELECT c FROM (SELECT f(..) AS c UNION SELECT ...) x HAVING a = c)
  
  In this way the c is referenced directly in the select list as well as by
  reference in the HAVING clause. So it gets correctly fixed even with
  prepared statements.
  
  And since the Item_null_helper subclass of Item_ref_null_helper is not used
  anywhere else it's taken out.

  sql/item_subselect.cc
    1.140 06/04/26 10:37:25 gkodinov@stripped +9 -7
    The described change to the IN->EXISTS transformation

  sql/item.h
    1.193 06/04/26 10:37:25 gkodinov@stripped +0 -13
    Taking out the Item_null_helper as it's no longer needed

  sql/item.cc
    1.232 06/04/26 10:37:25 gkodinov@stripped +0 -8
    Taking out the Item_null_helper as it's no longer needed

# 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:	gkodinov
# Host:	rakia.progem.bg
# Root:	/home/kgeorge/mysql/4.1/B18492

--- 1.231/sql/item.cc	2006-03-01 15:53:13 +02:00
+++ 1.232/sql/item.cc	2006-04-26 10:37:25 +03:00
@@ -2716,14 +2716,6 @@
 }
 
 
-void Item_null_helper::print(String *str)
-{
-  str->append("<null_helper>(", 14);
-  store->print(str);
-  str->append(')');
-}
-
-
 bool Item_default_value::eq(const Item *item, bool binary_cmp) const
 {
   return item->type() == DEFAULT_VALUE_ITEM && 

--- 1.192/sql/item.h	2005-10-12 23:27:47 +03:00
+++ 1.193/sql/item.h	2006-04-26 10:37:25 +03:00
@@ -1045,19 +1045,6 @@
   }
 };
 
-class Item_null_helper :public Item_ref_null_helper
-{
-  Item *store;
-public:
-  Item_null_helper(Item_in_subselect* master, Item *item,
-		   const char *table_name_par, const char *field_name_par)
-    :Item_ref_null_helper(master, &item, table_name_par, field_name_par),
-     store(item)
-    { ref= &store; }
-  void print(String *str);
-};
-
-
 /*
   The following class is used to optimize comparing of date and bigint columns
   We need to save the original item ('ref') to be able to call

--- 1.139/sql/item_subselect.cc	2005-08-13 07:45:07 +03:00
+++ 1.140/sql/item_subselect.cc	2006-04-26 10:37:25 +03:00
@@ -822,13 +822,13 @@
   }
   else
   {
-    select_lex->item_list.empty();
-    select_lex->item_list.push_back(new Item_int("Not_used",
-						 (longlong) 1, 21));
-    select_lex->ref_pointer_array[0]= select_lex->item_list.head();
     if (select_lex->table_list.elements)
     {
       Item *having= item, *orig_item= item;
+      select_lex->item_list.empty();
+      select_lex->item_list.push_back(new Item_int("Not_used",
+                                                   (longlong) 1, 21));
+      select_lex->ref_pointer_array[0]= select_lex->item_list.head();
       item= func->create(expr, item);
       if (!abort_on_null && orig_item->maybe_null)
       {
@@ -875,9 +875,11 @@
 	select_lex->having=
 	  join->having=
 	  func->create(expr,
-		       new Item_null_helper(this, item,
-					    (char *)"<no matter>",
-					    (char *)"<result>"));
+                       new Item_ref_null_helper(this,
+                                            select_lex->ref_pointer_array,
+                                            (char *)"<no matter>",
+                                            (char *)"<result>"));
+
 	select_lex->having_fix_field= 1;
 	if (join->having->fix_fields(thd, join->tables_list,
 				     0))