index_hint.h

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/* - mode: c; c-basic-offset: 2; indent-tabs-mode: nil; -*-
 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
 *
 *  Copyright (C) 2008-2009 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; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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

namespace drizzled {

/*
  String names used to print a statement with index hints.
  Keep in sync with index_hint_type.
*/
extern const char* index_hint_type_name[];
typedef unsigned char index_clause_map;

enum index_hint_type
{
  INDEX_HINT_IGNORE,
  INDEX_HINT_USE,
  INDEX_HINT_FORCE
};

/*
  Bits in index_clause_map : one for each possible FOR clause in
  USE/FORCE/IGNORE INDEX index hint specification
*/
#define INDEX_HINT_MASK_JOIN  (1)
#define INDEX_HINT_MASK_GROUP (1 << 1)
#define INDEX_HINT_MASK_ORDER (1 << 2)

#define INDEX_HINT_MASK_ALL (INDEX_HINT_MASK_JOIN | INDEX_HINT_MASK_GROUP | INDEX_HINT_MASK_ORDER)

/* Single element of an USE/FORCE/IGNORE INDEX list specified as a SQL hint  */
class Index_hint : public memory::SqlAlloc
{
public:
  /* The type of the hint : USE/FORCE/IGNORE */
  index_hint_type type;
  /* Where the hit applies to. A bitmask of INDEX_HINT_MASK_<place> values */
  index_clause_map clause;
  /*
    The index name. Empty (str=NULL) name represents an empty list
    USE INDEX () clause
  */
  const char* key_name;

  Index_hint(index_hint_type type_arg, index_clause_map clause_arg, const char *str) :
    type(type_arg), clause(clause_arg), key_name(str)
  {
  }

  void print(String&) const;
};

} /* namespace drizzled */