Remove clear_insert_values() because it was far from trivial to handle the cleanup in all cases

(Old code failed for INSERT ... ON DUPLICATE with prepared statements) 
Instead, always reset table->insert_values on open.

mysql-test/t/trigger.test

@@ -53,6 +53,7 @@ select @a;
 drop trigger t1.trg;
 drop table t1;
 
+--disable_ps_protocol
 # Before update trigger
 # (In future we will achieve this via proper error handling in triggers)
 create table t1 (aid int not null primary key, balance int not null default 0);
@@ -74,6 +75,7 @@ select * from t1|
 drop trigger t1.trg|
 drop table t1|
 delimiter ;|
+--enable_ps_protocol
 
 # After update trigger
 create table t1 (i int);

sql/sql_base.cc

@@ -1069,6 +1069,7 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
   table->outer_join= table->null_row= table->maybe_null= table->force_index= 0;
   table->status=STATUS_NO_RECORD;
   table->keys_in_use_for_query= table->keys_in_use;
+  table->insert_values= 0;
   table->used_keys= table->keys_for_keyread;
   if (table->timestamp_field)
     table->timestamp_field_type= table->timestamp_field->get_auto_set_type();

sql/sql_insert.cc

@@ -501,7 +501,6 @@ bool mysql_insert(THD *thd,TABLE_LIST *table_list,
     ::send_ok(thd, (ulong) thd->row_count_func, id, buff);
   }
   free_underlaid_joins(thd, &thd->lex->select_lex);
-  table_list->clear_insert_values();
   thd->abort_on_warning= 0;
   DBUG_RETURN(FALSE);
 
@@ -511,7 +510,6 @@ abort:
     end_delayed_insert(thd);
 #endif
   free_underlaid_joins(thd, &thd->lex->select_lex);
-  table_list->clear_insert_values();
   thd->abort_on_warning= 0;
   DBUG_RETURN(TRUE);
 }

sql/sql_parse.cc

@@ -3009,9 +3009,6 @@ create_error:
 	lex->select_lex.resolve_mode= SELECT_LEX::INSERT_MODE;
         delete result;
       }
-      /* in case of error first_table->table can be 0 */
-      if (first_table->table)
-        first_table->table->insert_values= 0;
       /* revert changes for SP */
       lex->select_lex.table_list.first= (byte*) first_table;
     }

sql/sql_prepare.cc

@@ -908,7 +908,11 @@ static bool mysql_test_insert(Prepared_statement *stmt,
     Item *unused_conds= 0;
 
     if (table_list->table)
-      table_list->table->insert_values=(byte *)1; // don't allocate insert_values
+    {
+      // don't allocate insert_values
+      table_list->table->insert_values=(byte *)1;
+    }
+
     if ((res= mysql_prepare_insert(thd, table_list, table_list->table, 
 				   fields, values, update_fields,
 				   update_values, duplic,
@@ -934,8 +938,7 @@ static bool mysql_test_insert(Prepared_statement *stmt,
   res= 0;
 error:
   lex->unit.cleanup();
-  if (table_list->table)
-    table_list->table->insert_values=0;
+  /* insert_values is cleared in open_table */
   DBUG_RETURN(res);
 }
 
@@ -1401,6 +1404,11 @@ static int mysql_test_insert_select(Prepared_statement *stmt,
   DBUG_ASSERT(first_local_table != 0);
   /* Skip first table, which is the table we are inserting in */
   lex->select_lex.table_list.first= (byte*) first_local_table->next_local;
+  if (tables->table)
+  {
+    // don't allocate insert_values
+    tables->table->insert_values=(byte *)1;
+  }
 
   /*
     insert/replace from SELECT give its SELECT_LEX for SELECT,

sql/table.cc

@@ -2026,26 +2026,6 @@ bool st_table_list::set_insert_values(MEM_ROOT *mem_root)
 }
 
 
-/*
-  clear insert_values reference
-
-    SYNOPSIS
-    clear_insert_values()
-*/
-
-void st_table_list::clear_insert_values()
-{
-  if (table)
-    table->insert_values= 0;
-  else
-  {
-    DBUG_ASSERT(view && ancestor && ancestor->next_local);
-    for (TABLE_LIST *tbl= ancestor; tbl; tbl= tbl->next_local)
-      tbl->clear_insert_values();
-  }
-}
-
-
 void Field_iterator_view::set(TABLE_LIST *table)
 {
   ptr= table->field_translation;

sql/table.h

@@ -387,7 +387,6 @@ typedef struct st_table_list
   void restore_want_privilege();
   bool check_single_table(st_table_list **table, table_map map);
   bool set_insert_values(MEM_ROOT *mem_root);
-  void clear_insert_values();
 } TABLE_LIST;
 
 class Item;