~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 DRIZZLE_SERVER_SQL_LEX_H

#define DRIZZLE_SERVER_SQL_LEX_H

/**

  @defgroup Semantic_Analysis Semantic Analysis

*/

#include <drizzled/sql_udf.h>

#include <drizzled/name_resolution_context.h>

#include <drizzled/item/subselect.h>

#include <drizzled/item/param.h>

#include <drizzled/item/outer_ref.h>

#include <drizzled/table_list.h>

#include <drizzled/function/real.h>

#include <drizzled/alter_drop.h>

#include <drizzled/alter_column.h>

#include <drizzled/key.h>

#include <drizzled/foreign_key.h>

#include <drizzled/item/param.h>

class select_result_interceptor;

class virtual_column_info;

/* YACC and LEX Definitions */

/* These may not be declared yet */

class Table_ident;

class sql_exchange;

class LEX_COLUMN;

class Item_outer_ref;

#ifdef DRIZZLE_SERVER

/*

  The following hack is needed because mysql_yacc.cc does not define

  YYSTYPE before including this file

*/

#include <drizzled/set_var.h>

#include <drizzled/item/func.h>

#ifdef DRIZZLE_YACC

#define LEX_YYSTYPE void *

#else

#if defined(DRIZZLE_LEX)

#include <drizzled/lex_symbol.h>

#include <drizzled/sql_yacc.h>

#define LEX_YYSTYPE YYSTYPE *

#else

#define LEX_YYSTYPE void *

#endif

#endif

#endif

// describe/explain types

#define DESCRIBE_NORMAL		1

#define DESCRIBE_EXTENDED	2

#ifdef DRIZZLE_SERVER

#define DERIVED_NONE	0

#define DERIVED_SUBQUERY	1

typedef List<Item> List_item;

/* SERVERS CACHE CHANGES */

typedef struct st_lex_server_options

{

  int32_t port;

  uint32_t server_name_length;

  char *server_name, *host, *db, *username, *password, *scheme, *owner;

} LEX_SERVER_OPTIONS;

typedef struct st_lex_master_info

{

  char *host, *user, *password, *log_file_name;

  uint32_t port, connect_retry;

  float heartbeat_period;

  uint64_t pos;

  uint32_t server_id;

  /*

    Enum is used for making it possible to detect if the user

    changed variable or if it should be left at old value

   */

  enum {LEX_MI_UNCHANGED, LEX_MI_DISABLE, LEX_MI_ENABLE} heartbeat_opt;

  char *relay_log_name;

  uint32_t relay_log_pos;

} LEX_MASTER_INFO;

enum sub_select_type

{

  UNSPECIFIED_TYPE,UNION_TYPE, INTERSECT_TYPE,

  EXCEPT_TYPE, GLOBAL_OPTIONS_TYPE, DERIVED_TABLE_TYPE, OLAP_TYPE

};

enum olap_type

{

  UNSPECIFIED_OLAP_TYPE, CUBE_TYPE, ROLLUP_TYPE

};

enum tablespace_op_type

{

  NO_TABLESPACE_OP, DISCARD_TABLESPACE, IMPORT_TABLESPACE

};

/*

  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;

/*

  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 Sql_alloc

{

public:

  /* The type of the hint : USE/FORCE/IGNORE */

  enum 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

  */

  LEX_STRING key_name;

  Index_hint (enum index_hint_type type_arg, index_clause_map clause_arg,

              char *str, uint32_t length) :

    type(type_arg), clause(clause_arg)

  {

    key_name.str= str;

    key_name.length= length;

  }

  void print(Session *session, String *str);

};

/*

  The state of the lex parsing for selects

   master and slaves are pointers to select_lex.

   master is pointer to upper level node.

   slave is pointer to lower level node

   select_lex is a SELECT without union

   unit is container of either

     - One SELECT

     - UNION of selects

   select_lex and unit are both inherited form select_lex_node

   neighbors are two select_lex or units on the same level

   All select describing structures linked with following pointers:

   - list of neighbors (next/prev) (prev of first element point to slave

     pointer of upper structure)

     - For select this is a list of UNION's (or one element list)

     - For units this is a list of sub queries for the upper level select

   - pointer to master (master), which is

     If this is a unit

       - pointer to outer select_lex

     If this is a select_lex

       - pointer to outer unit structure for select

   - pointer to slave (slave), which is either:

     If this is a unit:

       - first SELECT that belong to this unit

     If this is a select_lex

       - first unit that belong to this SELECT (subquries or derived tables)

   - list of all select_lex (link_next/link_prev)

     This is to be used for things like derived tables creation, where we

     go through this list and create the derived tables.

   If unit contain several selects (UNION now, INTERSECT etc later)

   then it have special select_lex called fake_select_lex. It used for

   storing global parameters (like ORDER BY, LIMIT) and executing union.

   Subqueries used in global ORDER BY clause will be attached to this

   fake_select_lex, which will allow them correctly resolve fields of

   'upper' UNION and outer selects.

   For example for following query:

   select *

     from table1

     where table1.field IN (select * from table1_1_1 union

                            select * from table1_1_2)

     union

   select *

     from table2

     where table2.field=(select (select f1 from table2_1_1_1_1

                                   where table2_1_1_1_1.f2=table2_1_1.f3)

                           from table2_1_1

                           where table2_1_1.f1=table2.f2)

     union

   select * from table3;

   we will have following structure:

   select1: (select * from table1 ...)

   select2: (select * from table2 ...)

   select3: (select * from table3)

   select1.1.1: (select * from table1_1_1)

   ...

     main unit

     fake0

     select1 select2 select3

     |^^     |^

    s|||     ||master

    l|||     |+---------------------------------+

    a|||     +---------------------------------+|

    v|||master                         slave   ||

    e||+-------------------------+             ||

     V|            neighbor      |             V|

     unit1.1<+==================>unit1.2       unit2.1

     fake1.1

     select1.1.1 select 1.1.2    select1.2.1   select2.1.1

                                               |^

                                               ||

                                               V|

                                               unit2.1.1.1

                                               select2.1.1.1.1

   relation in main unit will be following:

   (bigger picture for:

      main unit

      fake0

      select1 select2 select3

   in the above picture)

         main unit

         |^^^^|fake_select_lex

         |||||+--------------------------------------------+

         ||||+--------------------------------------------+|

         |||+------------------------------+              ||

         ||+--------------+                |              ||

    slave||master         |                |              ||

         V|      neighbor |       neighbor |        master|V

         select1<========>select2<========>select3        fake0

    list of all select_lex will be following (as it will be constructed by

    parser):

    select1->select2->select3->select2.1.1->select 2.1.2->select2.1.1.1.1-+

                                                                          |

    +---------------------------------------------------------------------+

    |

    +->select1.1.1->select1.1.2

*/

/*

    Base class for st_select_lex (SELECT_LEX) &

    st_select_lex_unit (SELECT_LEX_UNIT)

*/

class LEX;

class st_select_lex;

class st_select_lex_unit;

class st_select_lex_node {

protected:

  st_select_lex_node *next, **prev,   /* neighbor list */

    *master, *slave,                  /* vertical links */

    *link_next, **link_prev;          /* list of whole SELECT_LEX */

public:

  uint64_t options;

  /*

    result of this query can't be cached, bit field, can be :

      UNCACHEABLE_DEPENDENT

      UNCACHEABLE_RAND

      UNCACHEABLE_SIDEEFFECT

      UNCACHEABLE_EXPLAIN

      UNCACHEABLE_PREPARE

  */

  uint8_t uncacheable;

  enum sub_select_type linkage;

  bool no_table_names_allowed; /* used for global order by */

  bool no_error; /* suppress error message (convert it to warnings) */

  static void *operator new(size_t size)

  {

    return sql_alloc(size);

  }

  static void *operator new(size_t size, MEM_ROOT *mem_root)

  { return (void*) alloc_root(mem_root, (uint32_t) size); }

  static void operator delete(void *, size_t)

  { TRASH(ptr, size); }

  static void operator delete(void *, MEM_ROOT *)

  {}

  st_select_lex_node(): linkage(UNSPECIFIED_TYPE) {}

  virtual ~st_select_lex_node() {}

  inline st_select_lex_node* get_master() { return master; }

  virtual void init_query();

  virtual void init_select();

  void include_down(st_select_lex_node *upper);

  void include_neighbour(st_select_lex_node *before);

  void include_standalone(st_select_lex_node *sel, st_select_lex_node **ref);

  void include_global(st_select_lex_node **plink);

  void exclude();

  virtual st_select_lex_unit* master_unit()= 0;

  virtual st_select_lex* outer_select()= 0;

  virtual st_select_lex* return_after_parsing()= 0;

  virtual bool set_braces(bool value);

  virtual bool inc_in_sum_expr();

  virtual uint32_t get_in_sum_expr();

  virtual TableList* get_table_list();

  virtual List<Item>* get_item_list();

  virtual uint32_t get_table_join_options();

  virtual TableList *add_table_to_list(Session *session, Table_ident *table,

                                        LEX_STRING *alias,

                                        uint32_t table_options,

                                        thr_lock_type flags= TL_UNLOCK,

                                        List<Index_hint> *hints= 0,

                                        LEX_STRING *option= 0);

  virtual void set_lock_for_tables(thr_lock_type)

  {}

  friend class st_select_lex_unit;

  friend bool mysql_new_select(LEX *lex, bool move_down);

private:

  void fast_exclude();

};

typedef class st_select_lex_node SELECT_LEX_NODE;

/*

   SELECT_LEX_UNIT - unit of selects (UNION, INTERSECT, ...) group

   SELECT_LEXs

*/

class Session;

class select_result;

class JOIN;

class select_union;

class st_select_lex_unit: public st_select_lex_node {

protected:

  TableList result_table_list;

  select_union *union_result;

  Table *table; /* temporary table using for appending UNION results */

  select_result *result;

  uint64_t found_rows_for_union;

  bool saved_error;

public:

  bool  prepared, // prepare phase already performed for UNION (unit)

    optimized, // optimize phase already performed for UNION (unit)

    executed, // already executed

    cleaned;

  // list of fields which points to temporary table for union

  List<Item> item_list;

  /*

    list of types of items inside union (used for union & derived tables)

    Item_type_holders from which this list consist may have pointers to Field,

    pointers is valid only after preparing SELECTS of this unit and before

    any SELECT of this unit execution

    TODO:

    Possibly this member should be protected, and its direct use replaced

    by get_unit_column_types(). Check the places where it is used.

  */

  List<Item> types;

  /*

    Pointer to 'last' select or pointer to unit where stored

    global parameters for union

  */

  st_select_lex *global_parameters;

  //node on wich we should return current_select pointer after parsing subquery

  st_select_lex *return_to;

  /* LIMIT clause runtime counters */

  ha_rows select_limit_cnt, offset_limit_cnt;

  /* not NULL if unit used in subselect, point to subselect item */

  Item_subselect *item;

  /* thread handler */

  Session *session;

  /*

    SELECT_LEX for hidden SELECT in onion which process global

    ORDER BY and LIMIT

  */

  st_select_lex *fake_select_lex;

  st_select_lex *union_distinct; /* pointer to the last UNION DISTINCT */

  bool describe; /* union exec() called for EXPLAIN */

  void init_query();

  st_select_lex_unit* master_unit();

  st_select_lex* outer_select();

  st_select_lex* first_select()

  {

    return reinterpret_cast<st_select_lex*>(slave);

  }

  st_select_lex_unit* next_unit()

  {

    return reinterpret_cast<st_select_lex_unit*>(next);

  }

  st_select_lex* return_after_parsing() { return return_to; }

  void exclude_level();

  void exclude_tree();

  /* UNION methods */

  bool prepare(Session *session, select_result *result, uint32_t additional_options);

  bool exec();

  bool cleanup();

  inline void unclean() { cleaned= 0; }

  void reinit_exec_mechanism();

  void print(String *str, enum_query_type query_type);

  bool add_fake_select_lex(Session *session);

  void init_prepare_fake_select_lex(Session *session);

  bool change_result(select_result_interceptor *result,

                     select_result_interceptor *old_result);

  void set_limit(st_select_lex *values);

  void set_session(Session *session_arg) { session= session_arg; }

  inline bool is_union ();

  friend void lex_start(Session *session);

  friend int subselect_union_engine::exec();

  List<Item> *get_unit_column_types();

};

typedef class st_select_lex_unit SELECT_LEX_UNIT;

/*

  SELECT_LEX - store information of parsed SELECT statment

*/

class st_select_lex: public st_select_lex_node

{

public:

  Name_resolution_context context;

  char *db;

  Item *where, *having;                         /* WHERE & HAVING clauses */

  /* Saved values of the WHERE and HAVING clauses*/

  Item::cond_result cond_value, having_value;

  /* point on lex in which it was created, used in view subquery detection */

  LEX *parent_lex;

  enum olap_type olap;

  /* FROM clause - points to the beginning of the TableList::next_local list. */

  SQL_LIST	      table_list;

  SQL_LIST	      group_list; /* GROUP BY clause. */

  List<Item>          item_list;  /* list of fields & expressions */

  List<String>        interval_list;

  bool	              is_item_list_lookup;

  /*

    Despite their names, the following are used in unions. This should

    be rewritten. -Brian

  */

  List<Item_real_func> *ftfunc_list;

  List<Item_real_func> ftfunc_list_alloc;

  JOIN *join; /* after JOIN::prepare it is pointer to corresponding JOIN */

  List<TableList> top_join_list; /* join list of the top level          */

  List<TableList> *join_list;    /* list for the currently parsed join  */

  TableList *embedding;          /* table embedding to the above list   */

  List<TableList> sj_nests;

  /*

    Beginning of the list of leaves in a FROM clause, where the leaves

    inlcude all base tables including view tables. The tables are connected

    by TableList::next_leaf, so leaf_tables points to the left-most leaf.

  */

  TableList *leaf_tables;

  const char *type;               /* type of select for EXPLAIN          */

  SQL_LIST order_list;                /* ORDER clause */

  SQL_LIST *gorder_list;

  Item *select_limit, *offset_limit;  /* LIMIT clause parameters */

  // Arrays of pointers to top elements of all_fields list

  Item **ref_pointer_array;

  /*

    number of items in select_list and HAVING clause used to get number

    bigger then can be number of entries that will be added to all item

    list during split_sum_func

  */

  uint32_t select_n_having_items;

  uint32_t cond_count;    /* number of arguments of and/or/xor in where/having/on */

  uint32_t between_count; /* number of between predicates in where/having/on      */

  uint32_t max_equal_elems; /* maximal number of elements in multiple equalities  */

  /*

    Number of fields used in select list or where clause of current select

    and all inner subselects.

  */

  uint32_t select_n_where_fields;

  enum_parsing_place parsing_place; /* where we are parsing expression */

  bool with_sum_func;   /* sum function indicator */

  uint32_t table_join_options;

  uint32_t in_sum_expr;

  uint32_t select_number; /* number of select (used for EXPLAIN) */

  int nest_level;     /* nesting level of select */

  Item_sum *inner_sum_func_list; /* list of sum func in nested selects */

  uint32_t with_wild; /* item list contain '*' */

  bool  braces;   	/* SELECT ... UNION (SELECT ... ) <- this braces */

  /* true when having fix field called in processing of this SELECT */

  bool having_fix_field;

  /* List of references to fields referenced from inner selects */

  List<Item_outer_ref> inner_refs_list;

  /* Number of Item_sum-derived objects in this SELECT */

  uint32_t n_sum_items;

  /* Number of Item_sum-derived objects in children and descendant SELECTs */

  uint32_t n_child_sum_items;

  /* explicit LIMIT clause was used */

  bool explicit_limit;

  /*

    there are subquery in HAVING clause => we can't close tables before

    query processing end even if we use temporary table

  */

  bool subquery_in_having;

  /* true <=> this SELECT is correlated w.r.t. some ancestor select */

  bool is_correlated;

  /* exclude this select from check of unique_table() */

  bool exclude_from_table_unique_test;

  /* List of fields that aren't under an aggregate function */

  List<Item_field> non_agg_fields;

  /* index in the select list of the expression currently being fixed */

  int cur_pos_in_select_list;

  List<udf_func>     udf_list;                  /* udf function calls stack */

  /*

    This is a copy of the original JOIN USING list that comes from

    the parser. The parser :

      1. Sets the natural_join of the second TableList in the join

         and the st_select_lex::prev_join_using.

      2. Makes a parent TableList and sets its is_natural_join/

       join_using_fields members.

      3. Uses the wrapper TableList as a table in the upper level.

    We cannot assign directly to join_using_fields in the parser because

    at stage (1.) the parent TableList is not constructed yet and

    the assignment will override the JOIN USING fields of the lower level

    joins on the right.

  */

  List<String> *prev_join_using;

  /*

    Bitmap used in the ONLY_FULL_GROUP_BY_MODE to prevent mixture of aggregate

    functions and non aggregated fields when GROUP BY list is absent.

    Bits:

      0 - non aggregated fields are used in this select,

          defined as NON_AGG_FIELD_USED.

      1 - aggregate functions are used in this select,

          defined as SUM_FUNC_USED.

  */

  uint8_t full_group_by_flag;

  void init_query();

  void init_select();

  st_select_lex_unit* master_unit();

  st_select_lex_unit* first_inner_unit()

  {

    return (st_select_lex_unit*) slave;

  }

  st_select_lex* outer_select();

  st_select_lex* next_select() { return (st_select_lex*) next; }

  st_select_lex* next_select_in_list()

  {

    return (st_select_lex*) link_next;

  }

  st_select_lex_node** next_select_in_list_addr()

  {

    return &link_next;

  }

  st_select_lex* return_after_parsing()

  {

    return master_unit()->return_after_parsing();

  }

  void mark_as_dependent(st_select_lex *last);

  bool set_braces(bool value);

  bool inc_in_sum_expr();

  uint32_t get_in_sum_expr();

  bool add_item_to_list(Session *session, Item *item);

  bool add_group_to_list(Session *session, Item *item, bool asc);

  bool add_order_to_list(Session *session, Item *item, bool asc);

  TableList* add_table_to_list(Session *session, Table_ident *table,

				LEX_STRING *alias,

				uint32_t table_options,

				thr_lock_type flags= TL_UNLOCK,

				List<Index_hint> *hints= 0,

                                LEX_STRING *option= 0);

  TableList* get_table_list();

  bool init_nested_join(Session *session);

  TableList *end_nested_join(Session *session);

  TableList *nest_last_join(Session *session);

  void add_joined_table(TableList *table);

  TableList *convert_right_join();

  List<Item>* get_item_list();

  uint32_t get_table_join_options();

  void set_lock_for_tables(thr_lock_type lock_type);

  inline void init_order()

  {

    order_list.elements= 0;

    order_list.first= 0;

    order_list.next= (unsigned char**) &order_list.first;

  }

  /*

    This method created for reiniting LEX in mysql_admin_table() and can be

    used only if you are going remove all SELECT_LEX & units except belonger

    to LEX (LEX::unit & LEX::select, for other purposes there are

    SELECT_LEX_UNIT::exclude_level & SELECT_LEX_UNIT::exclude_tree

  */

  void cut_subtree() { slave= 0; }

  bool test_limit();

  friend void lex_start(Session *session);

  st_select_lex() : n_sum_items(0), n_child_sum_items(0) {}

  void make_empty_select()

  {

    init_query();

    init_select();

  }

  bool setup_ref_array(Session *session, uint32_t order_group_num);

  void print(Session *session, String *str, enum_query_type query_type);

  static void print_order(String *str,

                          order_st *order,

                          enum_query_type query_type);

  void print_limit(Session *session, String *str, enum_query_type query_type);

  void fix_prepare_information(Session *session, Item **conds, Item **having_conds);

  /*

    Destroy the used execution plan (JOIN) of this subtree (this

    SELECT_LEX and all nested SELECT_LEXes and SELECT_LEX_UNITs).

  */

  bool cleanup();

  /*

    Recursively cleanup the join of this select lex and of all nested

    select lexes.

  */

  void cleanup_all_joins(bool full);

  void set_index_hint_type(enum index_hint_type type, index_clause_map clause);

  /*

   Add a index hint to the tagged list of hints. The type and clause of the

   hint will be the current ones (set by set_index_hint())

  */

  bool add_index_hint (Session *session, char *str, uint32_t length);

  /* make a list to hold index hints */

  void alloc_index_hints (Session *session);

  /* read and clear the index hints */

  List<Index_hint>* pop_index_hints(void)

  {

    List<Index_hint> *hints= index_hints;

    index_hints= NULL;

    return hints;

  }

  void clear_index_hints(void) { index_hints= NULL; }

private:

  /* current index hint kind. used in filling up index_hints */

  enum index_hint_type current_index_hint_type;

  index_clause_map current_index_hint_clause;

  /* a list of USE/FORCE/IGNORE INDEX */

  List<Index_hint> *index_hints;

};

typedef class st_select_lex SELECT_LEX;

inline bool st_select_lex_unit::is_union ()

{

  return first_select()->next_select() &&

    first_select()->next_select()->linkage == UNION_TYPE;

}

#define ALTER_ADD_COLUMN	(1L << 0)

#define ALTER_DROP_COLUMN	(1L << 1)

#define ALTER_CHANGE_COLUMN	(1L << 2)

#define ALTER_COLUMN_STORAGE	(1L << 3)

#define ALTER_COLUMN_FORMAT	(1L << 4)

#define ALTER_COLUMN_ORDER      (1L << 5)

#define ALTER_ADD_INDEX		(1L << 6)

#define ALTER_DROP_INDEX	(1L << 7)

#define ALTER_RENAME		(1L << 8)

#define ALTER_ORDER		(1L << 9)

#define ALTER_OPTIONS		(1L << 10)

#define ALTER_COLUMN_DEFAULT    (1L << 11)

#define ALTER_KEYS_ONOFF        (1L << 12)

#define ALTER_STORAGE	        (1L << 13)

#define ALTER_ROW_FORMAT        (1L << 14)

#define ALTER_CONVERT           (1L << 15)

#define ALTER_FORCE		(1L << 16)

#define ALTER_RECREATE          (1L << 17)

#define ALTER_TABLE_REORG        (1L << 24)

#define ALTER_FOREIGN_KEY         (1L << 31)

/**

  @brief Parsing data for CREATE or ALTER Table.

  This structure contains a list of columns or indexes to be created,

  altered or dropped.

*/

class Alter_info

{

public:

  List<Alter_drop>              drop_list;

  List<Alter_column>            alter_list;

  List<Key>                     key_list;

  List<Create_field>            create_list;

  uint32_t                          flags;

  enum enum_enable_or_disable   keys_onoff;

  enum tablespace_op_type       tablespace_op;

  uint32_t                          no_parts;

  enum ha_build_method          build_method;

  Create_field                 *datetime_field;

  bool                          error_if_not_empty;

  Alter_info() :

    flags(0),

    keys_onoff(LEAVE_AS_IS),

    tablespace_op(NO_TABLESPACE_OP),

    no_parts(0),

    build_method(HA_BUILD_DEFAULT),

    datetime_field(NULL),

    error_if_not_empty(false)

  {}

  void reset()

  {

    drop_list.empty();

    alter_list.empty();

    key_list.empty();

    create_list.empty();

    flags= 0;

    keys_onoff= LEAVE_AS_IS;

    tablespace_op= NO_TABLESPACE_OP;

    no_parts= 0;

    build_method= HA_BUILD_DEFAULT;

    datetime_field= 0;

    error_if_not_empty= false;

  }

  Alter_info(const Alter_info &rhs, MEM_ROOT *mem_root);

private:

  Alter_info &operator=(const Alter_info &rhs); // not implemented

  Alter_info(const Alter_info &rhs);            // not implemented

};

enum xa_option_words {XA_NONE, XA_JOIN, XA_RESUME, XA_ONE_PHASE,

                      XA_SUSPEND, XA_FOR_MIGRATE};

extern const LEX_STRING null_lex_str;

/*

  Class representing list of all tables used by statement.

  It also contains information about stored functions used by statement

  since during its execution we may have to add all tables used by its

  stored functions/triggers to this list in order to pre-open and lock

  them.

  Also used by st_lex::reset_n_backup/restore_backup_query_tables_list()

  methods to save and restore this information.

*/

class Query_tables_list

{

public:

  /* Global list of all tables used by this statement */

  TableList *query_tables;

  /* Pointer to next_global member of last element in the previous list. */

  TableList **query_tables_last;

  /*

    If non-0 then indicates that query requires prelocking and points to

    next_global member of last own element in query table list (i.e. last

    table which was not added to it as part of preparation to prelocking).

    0 - indicates that this query does not need prelocking.

  */