~drizzle-trunk/drizzle/development

/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2008 Sun Microsystems, Inc.

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; version 2 of the License.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */

#pragma once

#include <drizzled/item.h>

namespace drizzled {

/**

 * Instances of Name_resolution_context store the information necesary for

 * name resolution of Items and other context analysis of a query made in

 * fix_fields().

 *

 * This structure is a part of Select_Lex, a pointer to this structure is

 * assigned when an item is created (which happens mostly during  parsing

 * (sql_yacc.yy)), but the structure itself will be initialized after parsing

 * is complete

 *

 * @todo

 *

 * Move subquery of INSERT ... SELECT and CREATE ... SELECT to

 * separate Select_Lex which allow to remove tricks of changing this

 * structure before and after INSERT/CREATE and its SELECT to make correct

 * field name resolution.

 */

class Name_resolution_context : public memory::SqlAlloc

{

public:

  /**

   * The name resolution context to search in when an Item cannot be

   * resolved in this context (the context of an outer select)

   */

  Name_resolution_context *outer_context;

  /**

   * List of tables used to resolve the items of this context.  Usually these

   * are tables from the FROM clause of SELECT statement.  The exceptions are

   * INSERT ... SELECT and CREATE ... SELECT statements, where SELECT

   * subquery is not moved to a separate Select_Lex.  For these types of

   * statements we have to change this member dynamically to ensure correct

   * name resolution of different parts of the statement.

   */

  TableList *table_list;

  /**

   * In most cases the two table references below replace 'table_list' above

   * for the purpose of name resolution. The first and last name resolution

   * table references allow us to search only in a sub-tree of the nested

   * join tree in a FROM clause. This is needed for NATURAL JOIN, JOIN ... USING

   * and JOIN ... ON.

   */

  TableList *first_name_resolution_table;

  /**

   * Last table to search in the list of leaf table references that begins

   * with first_name_resolution_table.

   */

  TableList *last_name_resolution_table;

  /**

   * Select_Lex item belong to, in case of merged VIEW it can differ from

   * Select_Lex where item was created, so we can't use table_list/field_list

   * from there

   */

  Select_Lex *select_lex;

  /**

   * When true items are resolved in this context both against the

   * SELECT list and this->table_list. If false, items are resolved

   * only against this->table_list.

   */

  bool resolve_in_select_list;

  /**

   * Security context of this name resolution context. It's used for views

   * and is non-zero only if the view is defined with SQL SECURITY DEFINER.

   */

  SecurityContext *security_ctx;

  Name_resolution_context()

    :

      outer_context(0), 

      table_list(0), 

      select_lex(0),

      security_ctx(0)

  {

  }

  inline void init()

  {

    resolve_in_select_list= false;

    first_name_resolution_table= NULL;

    last_name_resolution_table= NULL;

  }

  inline void resolve_in_table_list_only(TableList *tables)

  {

    table_list= first_name_resolution_table= tables;

    resolve_in_select_list= false;

  }

};

} /* namespace drizzled */