mariadb/sql/sql_truncate.h

#ifndef SQL_TRUNCATE_INCLUDED
#define SQL_TRUNCATE_INCLUDED
/* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.

   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 */

class THD;
struct TABLE_LIST;

/**
  Truncate_statement represents the TRUNCATE statement.
*/
class Truncate_statement : public Sql_statement
{
private:
  /* Set if a lock must be downgraded after truncate is done. */
  MDL_ticket *m_ticket_downgrade;

public:
  /**
    Constructor, used to represent a ALTER TABLE statement.
    @param lex the LEX structure for this statement.
  */
  Truncate_statement(LEX *lex)
    : Sql_statement(lex)
  {}

  virtual ~Truncate_statement()
  {}

  /**
    Execute a TRUNCATE statement at runtime.
    @param thd the current thread.
    @return false on success.
  */
  bool execute(THD *thd);

protected:
  /** Handle locking a base table for truncate. */
  bool lock_table(THD *, TABLE_LIST *, bool *);

  /** Truncate table via the handler method. */
  int handler_truncate(THD *, TABLE_LIST *, bool);

  /**
    Optimized delete of all rows by doing a full regenerate of the table.
    Depending on the storage engine, it can be accomplished through a
    drop and recreate or via the handler truncate method.
  */
  bool truncate_table(THD *, TABLE_LIST *);
};

#endif