Fixed BUG#822: Copying and clearing some things in thd/lex when

executing sub-statements (selects) prevents crashes intermittent
crashes.
Also fixed bug in sql_yacc.yy (generated a hpop instruction when
not needed).

mysql-test/r/sp.result

@@ -500,6 +500,23 @@ id	data
 hndlr3	13
 delete from t1;
 drop procedure hndlr3;
+create procedure bug822(a_id char(16), a_data int)
+begin
+declare n int;
+select count(*) into n from t1 where id = a_id and data = a_data;
+if n = 0 then
+insert into t1 (id, data) values (a_id, a_data);
+end if;
+end;
+call bug822('foo', 42);
+call bug822('foo', 42);
+call bug822('bar', 666);
+select * from t1;
+id	data
+foo	42
+bar	666
+delete from t1;
+drop procedure bug822;
 drop table if exists fac;
 create table fac (n int unsigned not null primary key, f bigint unsigned);
 create procedure ifac(n int unsigned)

mysql-test/t/sp.test

@@ -589,6 +589,23 @@ delete from t1|
 drop procedure hndlr3|
 
 
+create procedure bug822(a_id char(16), a_data int)
+begin
+  declare n int;
+  select count(*) into n from t1 where id = a_id and data = a_data;
+  if n = 0 then
+    insert into t1 (id, data) values (a_id, a_data);
+  end if;
+end|
+
+call bug822('foo', 42)|
+call bug822('foo', 42)|
+call bug822('bar', 666)|
+select * from t1|
+delete from t1|
+drop procedure bug822|
+
+
 #
 # Some "real" examples
 #

sql/sp_head.cc

@@ -481,6 +481,13 @@ sp_head::restore_lex(THD *thd)
   // Update some state in the old one first
   oldlex->ptr= sublex->ptr;
   oldlex->next_state= sublex->next_state;
+  // Save WHERE clause pointers to avoid damaging by optimisation
+  for (SELECT_LEX *sl= sublex->all_selects_list ;
+       sl ;
+       sl= sl->next_select_in_list())
+  {
+    sl->prep_where= sl->where;
+  }
 
   // Collect some data from the sub statement lex.
   sp_merge_funs(oldlex, sublex);
@@ -578,14 +585,31 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
   DBUG_ENTER("sp_instr_stmt::execute");
   DBUG_PRINT("info", ("command: %d", m_lex->sql_command));
   LEX *olex;			// The other lex
+  Item *freelist;
   int res;
 
   olex= thd->lex;		// Save the other lex
   thd->lex= m_lex;		// Use my own lex
   thd->lex->thd = thd;		// QQ Not reentrant!
   thd->lex->unit.thd= thd;	// QQ Not reentrant
+  freelist= thd->free_list;
+  thd->free_list= NULL;
+  thd->query_id= query_id++;
+
+  // Copy WHERE clause pointers to avoid damaging by optimisation
+  // Also clear ref_pointer_arrays.
+  for (SELECT_LEX *sl= m_lex->all_selects_list ;
+       sl ;
+       sl= sl->next_select_in_list())
+  {
+    sl->ref_pointer_array= 0;
+    if (sl->prep_where)
+      sl->where= sl->prep_where->copy_andor_structure(thd);
+    DBUG_ASSERT(sl->join == 0);
+  }
 
   res= mysql_execute_command(thd);
+
   if (thd->lock || thd->open_tables || thd->derived_tables)
   {
     thd->proc_info="closing tables";
@@ -593,6 +617,7 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
   }
 
   thd->lex= olex;		// Restore the other lex
+  thd->free_list= freelist;
 
   *nextp = m_ip+1;
   DBUG_RETURN(res);

sql/sql_yacc.yy

@@ -1644,14 +1644,16 @@ sp_unlabeled_control:
 	    LEX *lex= Lex;
 	    sp_head *sp= lex->sphead;
 	    sp_pcontext *ctx= lex->spcont;
-	    sp_instr_hpop *i;
 
   	    sp->backpatch(ctx->pop_label());
 	    ctx->pop_pvar($3.vars);
 	    ctx->pop_cond($3.conds);
-	    i= new sp_instr_hpop(sp->instructions(), $3.hndlrs);
+	    if ($3.hndlrs)
+	    {
+	      sp_instr_hpop *i= new sp_instr_hpop(sp->instructions(),$3.hndlrs);
 	      sp->add_instr(i);
 	    }
+	  }
 	| LOOP_SYM
 	  sp_proc_stmts END LOOP_SYM
 	  {