Fix for a bug record #307.

Very nasty bug.
It was caused by double free()-ing memory of join->select and 
join->quick. 

I was able to pinpoint it only after using Valgrind.

Plus better fix for bug with TMP_TABLE_PARAM.

Plus new constructor for SELECT_LEX.

mysql-test/r/innodb.result

@@ -1203,3 +1203,15 @@ a	b
 8	5
 9	5
 drop table t1,t2;
+CREATE TABLE t1 (col1 int(1))TYPE=InnoDB;
+CREATE TABLE t2 (col1 int(1),stamp TIMESTAMP(+0),INDEX stamp_idx
+(stamp))TYPE=InnoDB;
+insert into t1 values (1),(2),(3);
+insert into t2 values (1, 20020204130000),(2, 20020204130000),(4,20020204310000 );
+SELECT col1 FROM t1 UNION SELECT col1 FROM t2 WHERE stamp <
+'20020204120000' GROUP BY col1;
+col1
+1
+2
+3
+drop table t1,t2;

mysql-test/t/innodb.test

@@ -805,3 +805,11 @@ select * from t1;
 select * from t2;
 
 drop table t1,t2;
+CREATE TABLE t1 (col1 int(1))TYPE=InnoDB;
+CREATE TABLE t2 (col1 int(1),stamp TIMESTAMP(+0),INDEX stamp_idx
+(stamp))TYPE=InnoDB;
+insert into t1 values (1),(2),(3);
+insert into t2 values (1, 20020204130000),(2, 20020204130000),(4,20020204310000 );
+SELECT col1 FROM t1 UNION SELECT col1 FROM t2 WHERE stamp <
+'20020204120000' GROUP BY col1;
+drop table t1,t2;

sql/sql_lex.cc

@@ -1365,6 +1365,17 @@ ulong st_select_lex::get_table_join_options()
   return table_join_options;
 }
 
+st_select_lex::st_select_lex(struct st_lex *lex)
+{
+  select_number= ++lex->thd->select_number;
+  init_query();
+  init_select();
+  include_neighbour(lex->current_select);
+  include_global((st_select_lex_node**)&lex->all_selects_list);
+  lex->current_select= this;
+}
+
+
 /*
   There are st_select_lex::add_table_to_list & 
   st_select_lex::set_lock_for_tables in sql_parse.cc

sql/sql_lex.h

@@ -396,6 +396,8 @@ public:
   }
   
   friend void mysql_init_query(THD *thd);
+  st_select_lex(struct st_lex *lex);
+  st_select_lex() {;}
   void make_empty_select(st_select_lex *last_select)
   {
     select_number=INT_MAX;
@@ -478,7 +480,7 @@ typedef struct st_lex
   CHARSET_INFO *charset;
   char *help_arg;
   SQL_LIST *gorder_list;
-
+  st_lex() {;}
   inline void uncacheable()
   {
     safe_to_cache_query= 0;

sql/sql_select.cc

@@ -1281,9 +1281,18 @@ JOIN::cleanup(THD *thd)
       JOIN_TAB *tab, *end;
       for (tab= join_tab, end= tab+tables ; tab != end ; tab++)
       {
-	delete tab->select;
-	delete tab->quick;
+	if (tab->select)
+	{
+	  delete tab->select;
+	  tab->select=0;
+	}
+	if (tab->quick)
+	{
+	  delete tab->quick;
+	  tab->quick=0;
+	}
 	x_free(tab->cache.buff);
+	tab->cache.buff= 0;
       }
     }
     tmp_join->tmp_join= 0;
@@ -3283,8 +3292,16 @@ join_free(JOIN *join, bool full)
     {
       for (tab=join->join_tab,end=tab+join->tables ; tab != end ; tab++)
       {
-	delete tab->select;
-	delete tab->quick;
+	if (tab->select)
+	{
+	  delete tab->select;
+	  tab->select=0;
+	}
+	if (tab->quick)
+	{
+	  delete tab->quick;
+	  tab->quick=0;
+	}
 	x_free(tab->cache.buff);
 	tab->cache.buff= 0;
 	if (tab->table)

sql/sql_union.cc

@@ -124,10 +124,11 @@ int st_select_lex_unit::prepare(THD *thd, select_result *sel_result,
   prepared= 1;
   res= 0;
   found_rows_for_union= 0;
-  TMP_TABLE_PARAM *tmp_table_param= (TMP_TABLE_PARAM *)sql_calloc(sizeof(TMP_TABLE_PARAM));
+  TMP_TABLE_PARAM tmp_table_param;
   result= sel_result;
   t_and_f= tables_and_fields_initied;
-
+  
+  bzero((char *)&tmp_table_param,sizeof(TMP_TABLE_PARAM));
   thd->lex.current_select= select_cursor= first_select_in_union();
   /* Global option */
   if (((void*)(global_parameters)) == ((void*)this))
@@ -167,8 +168,8 @@ int st_select_lex_unit::prepare(THD *thd, select_result *sel_result,
     t_and_f= 1;
   }
 
-  tmp_table_param->field_count=item_list.elements;
-  if (!(table= create_tmp_table(thd, tmp_table_param, item_list,
+  tmp_table_param.field_count=item_list.elements;
+  if (!(table= create_tmp_table(thd, &tmp_table_param, item_list,
 				(ORDER*) 0, !union_option,
 				1, (select_cursor->options | thd->options |
 				    TMP_TABLE_ALL_COLUMNS),
@@ -185,7 +186,8 @@ int st_select_lex_unit::prepare(THD *thd, select_result *sel_result,
     goto err;
 
   union_result->not_describe=1;
-  union_result->tmp_table_param=tmp_table_param;
+  if (!(union_result->tmp_table_param=(TMP_TABLE_PARAM *)thd->memdup((char *)&tmp_table_param, sizeof(TMP_TABLE_PARAM))))
+    goto err;
 
   /*
     The following piece of code is placed here solely for the purpose of 
@@ -250,11 +252,9 @@ int st_select_lex_unit::exec()
 {
   int do_print_slow= 0;
   SELECT_LEX_NODE *lex_select_save= thd->lex.current_select;
-  SELECT_LEX *select_cursor=first_select_in_union(), *last_select;
+  SELECT_LEX *select_cursor=first_select_in_union();
   DBUG_ENTER("st_select_lex_unit::exec");
 
-  LINT_INIT(last_select);
-
   if (executed && !(dependent || uncacheable))
     DBUG_RETURN(0);
   executed= 1;
@@ -269,7 +269,6 @@ int st_select_lex_unit::exec()
     }
     for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())
     {
-      last_select=sl;
       if (optimized)
 	res= sl->join->reinit();
       else
@@ -335,8 +334,7 @@ int st_select_lex_unit::exec()
 
     if (!thd->is_fatal_error)			// Check if EOM
     {
-      SELECT_LEX *fake_select  = new SELECT_LEX();
-      fake_select->make_empty_select(last_select);
+      SELECT_LEX *fake_select  = new SELECT_LEX(&thd->lex);
       offset_limit_cnt= (select_cursor->braces ?
 			 global_parameters->offset_limit : 0);
       select_limit_cnt= (select_cursor->braces ?