~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

 *

 *  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

 */

#ifndef DRIZZLED_NAME_RESOLUTION_CONTEXT_H

#define DRIZZLED_NAME_RESOLUTION_CONTEXT_H

class TableList;

class Security_context;

class Session;

class st_select_lex;

/*

  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 Sql_alloc

{

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

  */

  st_select_lex *select_lex;

  /*

    Processor of errors caused during Item name resolving, now used only to

    hide underlying tables in errors about views (i.e. it substitute some

    errors for views)

  */

  void (*error_processor)(Session *, void *);

  void *error_processor_data;

  /*

    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.

  */

  Security_context *security_ctx;

  Name_resolution_context()

    :outer_context(0), table_list(0), select_lex(0),

     error_processor_data(0),

     security_ctx(0)

    {}

  void init()

    {

      resolve_in_select_list= false;

      error_processor= &dummy_error_processor;

      first_name_resolution_table= NULL;

      last_name_resolution_table= NULL;

    }

  void resolve_in_table_list_only(TableList *tables)

    {

      table_list= first_name_resolution_table= tables;

      resolve_in_select_list= false;

    }

  void process_error(Session *session)

    {

      (*error_processor)(session, error_processor_data);

    }

};

#endif /* DRIZZLED_NAME_RESOLUTION_CONTEXT_H */