Drizzled Public API Documentation

ref_null_helper.h
00001 /* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
00002  *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
00003  *
00004  *  Copyright (C) 2008 Sun Microsystems, Inc.
00005  *
00006  *  This program is free software; you can redistribute it and/or modify
00007  *  it under the terms of the GNU General Public License as published by
00008  *  the Free Software Foundation; version 2 of the License.
00009  *
00010  *  This program is distributed in the hope that it will be useful,
00011  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
00012  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00013  *  GNU General Public License for more details.
00014  *
00015  *  You should have received a copy of the GNU General Public License
00016  *  along with this program; if not, write to the Free Software
00017  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
00018  */
00019 
00020 #pragma once
00021 
00022 /*
00023   An object of this class:
00024    - Converts val_XXX() calls to ref->val_XXX_result() calls, like Item_ref.
00025    - Sets owner->was_null=true if it has returned a NULL value from any
00026      val_XXX() function. This allows to inject an Item_ref_null_helper
00027      object into subquery and then check if the subquery has produced a row
00028      with NULL value.
00029 */
00030 
00031 namespace drizzled
00032 {
00033 
00034 class Item_ref_null_helper: public Item_ref
00035 {
00036 protected:
00037   Item_in_subselect* owner;
00038 public:
00039   Item_ref_null_helper(Name_resolution_context *context_arg,
00040                        Item_in_subselect* master, Item **item,
00041                        const char *table_name_arg, const char *field_name_arg)
00042     :Item_ref(context_arg, item, table_name_arg, field_name_arg),
00043      owner(master) {}
00044   double val_real();
00045   int64_t val_int();
00046   String* val_str(String* s);
00047   type::Decimal *val_decimal(type::Decimal *);
00048   bool val_bool();
00049   bool get_date(type::Time &ltime, uint32_t fuzzydate);
00050   virtual void print(String *str);
00051   /*
00052     we add RAND_TABLE_BIT to prevent moving this item from HAVING to WHERE
00053   */
00054   table_map used_tables() const
00055   {
00056     return (depended_from ?
00057             OUTER_REF_TABLE_BIT :
00058             (*ref)->used_tables() | RAND_TABLE_BIT);
00059   }
00060 };
00061 
00062 } /* namespace drizzled */
00063