path: root/sql/sql_select.h

/* Copyright (c) 2000, 2010, Oracle and/or its affiliates.

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


#ifndef SQL_SELECT_INCLUDED
#define SQL_SELECT_INCLUDED
/**
  @file

  @brief
  classes to use when handling where clause
*/

#ifdef USE_PRAGMA_INTERFACE
#pragma interface			/* gcc class implementation */
#endif

#include "procedure.h"
#include <myisam.h>

#if defined(WITH_ARIA_STORAGE_ENGINE) && defined(USE_MARIA_FOR_TMP_TABLES)
#include "../storage/maria/ha_maria.h"
#define TMP_ENGINE_HTON maria_hton
#else
#define TMP_ENGINE_HTON myisam_hton
#endif
/* Values in optimize */
#define KEY_OPTIMIZE_EXISTS		1
#define KEY_OPTIMIZE_REF_OR_NULL	2
#define KEY_OPTIMIZE_EQ	                4

inline uint get_hash_join_key_no() { return MAX_KEY; }

inline bool is_hash_join_key_no(uint key) { return key == MAX_KEY; }

typedef struct keyuse_t {
  TABLE *table;
  Item	*val;				/**< or value if no field */
  table_map used_tables;
  uint	key, keypart, optimize;
  key_part_map keypart_map;
  ha_rows      ref_table_rows;
  /**
    If true, the comparison this value was created from will not be
    satisfied if val has NULL 'value'.
  */
  bool null_rejecting;
  /*
    !NULL - This KEYUSE was created from an equality that was wrapped into
            an Item_func_trig_cond. This means the equality (and validity of 
            this KEYUSE element) can be turned on and off. The on/off state 
            is indicted by the pointed value:
              *cond_guard == TRUE <=> equality condition is on
              *cond_guard == FALSE <=> equality condition is off

    NULL  - Otherwise (the source equality can't be turned off)
  */
  bool *cond_guard;
  /*
     0..64    <=> This was created from semi-join IN-equality # sj_pred_no.
     MAX_UINT  Otherwise
  */
  uint         sj_pred_no;

  bool is_for_hash_join() { return is_hash_join_key_no(key); }
} KEYUSE;

class store_key;

const int NO_REF_PART= uint(-1);

typedef struct st_table_ref
{
  bool		key_err;
  /** True if something was read into buffer in join_read_key.  */
  bool          has_record;
  uint          key_parts;                ///< num of ...
  uint          key_length;               ///< length of key_buff
  int           key;                      ///< key no
  uchar         *key_buff;                ///< value to look for with key
  uchar         *key_buff2;               ///< key_buff+key_length
  store_key     **key_copy;               //
  Item          **items;                  ///< val()'s for each keypart
  /*  
    Array of pointers to trigger variables. Some/all of the pointers may be
    NULL.  The ref access can be used iff
    
      for each used key part i, (!cond_guards[i] || *cond_guards[i]) 

    This array is used by subquery code. The subquery code may inject
    triggered conditions, i.e. conditions that can be 'switched off'. A ref 
    access created from such condition is not valid when at least one of the 
    underlying conditions is switched off (see subquery code for more details)
  */
  bool          **cond_guards;
  /**
    (null_rejecting & (1<<i)) means the condition is '=' and no matching
    rows will be produced if items[i] IS NULL (see add_not_null_conds())
  */
  key_part_map  null_rejecting;
  table_map	depend_map;		  ///< Table depends on these tables.

  /* null byte position in the key_buf. Used for REF_OR_NULL optimization */
  uchar          *null_ref_key;
  /* 
    ref_or_null optimization: number of key part that alternates between
    the lookup value or NULL (there's only one such part). 
    If we're not using ref_or_null, the value is NO_REF_PART
  */
  uint           null_ref_part;

  /*
    The number of times the record associated with this key was used
    in the join.
  */
  ha_rows       use_count;

  /*
    TRUE <=> disable the "cache" as doing lookup with the same key value may
    produce different results (because of Index Condition Pushdown)

  */
  bool          disable_cache;

  bool tmp_table_index_lookup_init(THD *thd, KEY *tmp_key, Item_iterator &it,
                                   bool value);
} TABLE_REF;


/*
  The structs which holds the join connections and join states
*/
enum join_type { JT_UNKNOWN,JT_SYSTEM,JT_CONST,JT_EQ_REF,JT_REF,JT_MAYBE_REF,
		 JT_ALL, JT_RANGE, JT_NEXT, JT_FT, JT_REF_OR_NULL,
		 JT_UNIQUE_SUBQUERY, JT_INDEX_SUBQUERY, JT_INDEX_MERGE,
                 JT_HASH, JT_HASH_RANGE, JT_HASH_NEXT, JT_HASH_INDEX_MERGE};

class JOIN;

enum enum_nested_loop_state
{
  NESTED_LOOP_KILLED= -2, NESTED_LOOP_ERROR= -1,
  NESTED_LOOP_OK= 0, NESTED_LOOP_NO_MORE_ROWS= 1,
  NESTED_LOOP_QUERY_LIMIT= 3, NESTED_LOOP_CURSOR_LIMIT= 4
};


/* Values for JOIN_TAB::packed_info */
#define TAB_INFO_HAVE_VALUE 1
#define TAB_INFO_USING_INDEX 2
#define TAB_INFO_USING_WHERE 4
#define TAB_INFO_FULL_SCAN_ON_NULL 8

typedef enum_nested_loop_state
(*Next_select_func)(JOIN *, struct st_join_table *, bool);
typedef int (*Read_record_func)(struct st_join_table *tab);
Next_select_func setup_end_select_func(JOIN *join);
int rr_sequential(READ_RECORD *info);


class JOIN_CACHE;
class SJ_TMP_TABLE;

typedef struct st_join_table {
  st_join_table() {}                          /* Remove gcc warning */
  TABLE		*table;
  KEYUSE	*keyuse;			/**< pointer to first used key */
  KEY           *hj_key;       /**< descriptor of the used best hash join key
				    not supported by any index                 */
  SQL_SELECT	*select;
  COND		*select_cond;
  COND          *on_precond;    /**< part of on condition to check before
				     accessing the first inner table           */  
  QUICK_SELECT_I *quick;
  /* 
    The value of select_cond before we've attempted to do Index Condition
    Pushdown. We may need to restore everything back if we first choose one
    index but then reconsider (see test_if_skip_sort_order() for such
    scenarios).
    NULL means no index condition pushdown was performed.
  */
  Item          *pre_idx_push_select_cond;
  Item	       **on_expr_ref;   /**< pointer to the associated on expression   */
  COND_EQUAL    *cond_equal;    /**< multiple equalities for the on expression */
  st_join_table *first_inner;   /**< first inner table for including outerjoin */
  bool           found;         /**< true after all matches or null complement */
  bool           not_null_compl;/**< true before null complement is added      */
  st_join_table *last_inner;    /**< last table table for embedding outer join */
  st_join_table *first_upper;  /**< first inner table for embedding outer join */
  st_join_table *first_unmatched; /**< used for optimization purposes only     */
  
  /* Special content for EXPLAIN 'Extra' column or NULL if none */
  const char	*info;
  /* 
    Bitmap of TAB_INFO_* bits that encodes special line for EXPLAIN 'Extra'
    column, or 0 if there is no info.
  */
  uint          packed_info;

  Read_record_func read_first_record;
  Next_select_func next_select;
  READ_RECORD	read_record;
  /* 
    Currently the following two fields are used only for a [NOT] IN subquery
    if it is executed by an alternative full table scan when the left operand of
    the subquery predicate is evaluated to NULL.
  */  
  Read_record_func save_read_first_record;/* to save read_first_record */ 
  int (*save_read_record) (READ_RECORD *);/* to save read_record.read_record */
  double	worst_seeks;
  key_map	const_keys;			/**< Keys with constant part */
  key_map	checked_keys;			/**< Keys checked in find_best */
  key_map	needed_reg;
  key_map       keys;                           /**< all keys with can be used */

  /* Either #rows in the table or 1 for const table.  */
  ha_rows	records;
  /*
    Number of records that will be scanned (yes scanned, not returned) by the
    best 'independent' access method, i.e. table scan or QUICK_*_SELECT)
  */
  ha_rows       found_records;
  /*
    Cost of accessing the table using "ALL" or range/index_merge access
    method (but not 'index' for some reason), i.e. this matches method which
    E(#records) is in found_records.
  */
  ha_rows       read_time;
    
  double        partial_join_cardinality;

  table_map	dependent,key_dependent;
  uint		use_quick,index;
  uint		status;				///< Save status for cache
  uint		used_fields;
  ulong         used_fieldlength;
  ulong         max_used_fieldlength;
  uint          used_blobs;
  uint          used_null_fields;
  uint          used_rowid_fields;
  uint          used_uneven_bit_fields;
  enum join_type type;
  bool		cached_eq_ref_table,eq_ref_table,not_used_in_distinct;
  bool		sorted;
  /* 
    If it's not 0 the number stored this field indicates that the index
    scan has been chosen to access the table data and we expect to scan 
    this number of rows for the table.
  */ 
  ha_rows       limit; 
  TABLE_REF	ref;
  /* TRUE <=> condition pushdown supports other tables presence */
  bool          icp_other_tables_ok;
  /* 
    TRUE <=> condition pushed to the index has to be factored out of
    the condition pushed to the table
  */
  bool          idx_cond_fact_out;
  bool          use_join_cache;
  uint          used_join_cache_level;
  ulong         join_buffer_size_limit;
  JOIN_CACHE	*cache;
  /*
    Index condition for BKA access join
  */
  Item          *cache_idx_cond;
  SQL_SELECT    *cache_select;
  JOIN		*join;
  /*
    Embedding SJ-nest (may be not the direct parent), or NULL if none.
    This variable holds the result of table pullout.
  */
  TABLE_LIST    *emb_sj_nest;

  /* FirstMatch variables (final QEP) */
  struct st_join_table *first_sj_inner_tab;
  struct st_join_table *last_sj_inner_tab;

  /* Variables for semi-join duplicate elimination */
  SJ_TMP_TABLE  *flush_weedout_table;
  SJ_TMP_TABLE  *check_weed_out_table;
  
  /*
    If set, means we should stop join enumeration after we've got the first
    match and return to the specified join tab. May point to
    join->join_tab[-1] which means stop join execution after the first
    match.
  */
  struct st_join_table  *do_firstmatch;
 
  /* 
     ptr  - We're doing a LooseScan, this join tab is the first (i.e. 
            "driving") join tab), and ptr points to the last join tab
            handled by the strategy. loosescan_match_tab->found_match
            should be checked to see if the current value group had a match.
     NULL - Not doing a loose scan on this join tab.
  */
  struct st_join_table *loosescan_match_tab;

  /* Buffer to save index tuple to be able to skip duplicates */
  uchar *loosescan_buf;
  
  /* Length of key tuple (depends on #keyparts used) to store in the above */
  uint loosescan_key_len;

  /* Used by LooseScan. TRUE<=> there has been a matching record combination */
  bool found_match;
  
  /*
    Used by DuplicateElimination. tab->table->ref must have the rowid
    whenever we have a current record.
  */
  int  keep_current_rowid;

  /* NestedOuterJoins: Bitmap of nested joins this table is part of */
  nested_join_map embedding_map;

  /*
    Semi-join strategy to be used for this join table. This is a copy of
    POSITION::sj_strategy field. This field is set up by the
    fix_semijion_strategies_for_picked_join_order.
  */
  uint sj_strategy;

  struct st_join_table *first_sjm_sibling;

  void cleanup();
  inline bool is_using_loose_index_scan()
  {
    return (select && select->quick &&
            (select->quick->get_type() ==
             QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX));
  }
  bool check_rowid_field()
  {
    if (keep_current_rowid && !used_rowid_fields)
    {
      used_rowid_fields= 1;
      used_fieldlength+= table->file->ref_length;
    }
    return test(used_rowid_fields);
  }
  bool is_inner_table_of_semi_join_with_first_match()
  {
    return first_sj_inner_tab != NULL;
  }
  bool is_inner_table_of_outer_join()
  {
    return first_inner != NULL;
  }
  bool is_single_inner_of_semi_join_with_first_match()
  {
    return first_sj_inner_tab == this && last_sj_inner_tab == this;            
  }
  bool is_single_inner_of_outer_join()
  {
    return first_inner == this && first_inner->last_inner == this;
  }
  bool is_first_inner_for_outer_join()
  {
    return first_inner && first_inner == this;
  }
  bool use_match_flag()
  {
    return is_first_inner_for_outer_join() || first_sj_inner_tab == this ; 
  }
  bool check_only_first_match()
  {
    return is_inner_table_of_semi_join_with_first_match() ||
           (is_inner_table_of_outer_join() &&
            table->reginfo.not_exists_optimize);
  }
  bool is_last_inner_table()
  {
    return (first_inner && first_inner->last_inner == this) ||
           last_sj_inner_tab == this;
  }
  /*
    Check whether the table belongs to a nest of inner tables of an
    outer join or to a nest of inner tables of a semi-join
  */
  bool is_nested_inner()
  {
    if (first_inner && 
        (first_inner != first_inner->last_inner || first_inner->first_upper))
      return TRUE;
    if (first_sj_inner_tab && first_sj_inner_tab != last_sj_inner_tab)
      return TRUE;
    return FALSE;
  }
  struct st_join_table *get_first_inner_table()
  {
    if (first_inner)
      return first_inner;
    return first_sj_inner_tab; 
  }
  void set_select_cond(COND *to, uint line)
  {
    DBUG_PRINT("info", ("select_cond changes %p -> %p at line %u tab %p",
                        select_cond, to, line, this));
    select_cond= to;
  }
  COND *set_cond(COND *new_cond)
  {
    COND *tmp_select_cond= select_cond;
    set_select_cond(new_cond, __LINE__);
    if (select)
      select->cond= new_cond;
    return tmp_select_cond;
  }
  void calc_used_field_length(bool max_fl);
  ulong get_used_fieldlength()
  {
    if (!used_fieldlength)
      calc_used_field_length(FALSE);
    return used_fieldlength;
  }
  ulong get_max_used_fieldlength()
  {
    if (!max_used_fieldlength)
      calc_used_field_length(TRUE);
    return max_used_fieldlength;
  }
  double get_partial_join_cardinality() { return partial_join_cardinality; }
  bool hash_join_is_possible();
  int make_scan_filter();
  bool is_ref_for_hash_join() { return is_hash_join_key_no(ref.key); }
  KEY *get_keyinfo_by_key_no(uint key) 
  {
    return (is_hash_join_key_no(key) ? hj_key : table->key_info+key);
  }
} JOIN_TAB;


#include "sql_join_cache.h"

enum_nested_loop_state sub_select_cache(JOIN *join, JOIN_TAB *join_tab, bool
                                        end_of_records);
enum_nested_loop_state sub_select(JOIN *join,JOIN_TAB *join_tab, bool
                                  end_of_records);
enum_nested_loop_state sub_select_sjm(JOIN *join, JOIN_TAB *join_tab, 
                                      bool end_of_records);

enum_nested_loop_state
end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
	       bool end_of_records);
enum_nested_loop_state
end_write_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
		bool end_of_records);


/**
  Information about a position of table within a join order. Used in join
  optimization.
*/
typedef struct st_position
{
  /*
    The "fanout": number of output rows that will be produced (after
    pushed down selection condition is applied) per each row combination of
    previous tables.
  */
  double records_read;

  /* 
    Cost accessing the table in course of the entire complete join execution,
    i.e. cost of one access method use (e.g. 'range' or 'ref' scan ) times 
    number the access method will be invoked.
  */
  double read_time;
  JOIN_TAB *table;

  /*
    NULL  -  'index' or 'range' or 'index_merge' or 'ALL' access is used.
    Other - [eq_]ref[_or_null] access is used. Pointer to {t.keypart1 = expr}
  */
  KEYUSE *key;

  /* If ref-based access is used: bitmap of tables this table depends on  */
  table_map ref_depend_map;

  bool use_join_buffer; 
  
  
  /* These form a stack of partial join order costs and output sizes */
  COST_VECT prefix_cost;
  double    prefix_record_count;

  /*
    Current optimization state: Semi-join strategy to be used for this
    and preceding join tables.
    
    Join optimizer sets this for the *last* join_tab in the
    duplicate-generating range. That is, in order to interpret this field, 
    one needs to traverse join->[best_]positions array from right to left.
    When you see a join table with sj_strategy!= SJ_OPT_NONE, some other
    field (depending on the strategy) tells how many preceding positions 
    this applies to. The values of covered_preceding_positions->sj_strategy
    must be ignored.
  */
  uint sj_strategy;
  /*
    Valid only after fix_semijoin_strategies_for_picked_join_order() call:
    if sj_strategy!=SJ_OPT_NONE, this is the number of subsequent tables that
    are covered by the specified semi-join strategy
  */
  uint n_sj_tables;

/* LooseScan strategy members */

  /* The first (i.e. driving) table we're doing loose scan for */
  uint        first_loosescan_table;
  /* 
     Tables that need to be in the prefix before we can calculate the cost
     of using LooseScan strategy.
  */
  table_map   loosescan_need_tables;

  /*
    keyno  -  Planning to do LooseScan on this key. If keyuse is NULL then 
              this is a full index scan, otherwise this is a ref+loosescan
              scan (and keyno matches the KEUSE's)
    MAX_KEY - Not doing a LooseScan
  */
  uint loosescan_key;  // final (one for strategy instance )
  uint loosescan_parts; /* Number of keyparts to be kept distinct */
  
/* FirstMatch strategy */
  /*
    Index of the first inner table that we intend to handle with this
    strategy
  */
  uint first_firstmatch_table;
  /*
    Tables that were not in the join prefix when we've started considering 
    FirstMatch strategy.
  */
  table_map first_firstmatch_rtbl;
  /* 
    Tables that need to be in the prefix before we can calculate the cost
    of using FirstMatch strategy.
   */
  table_map firstmatch_need_tables;


/* Duplicate Weedout strategy */
  /* The first table that the strategy will need to handle */
  uint  first_dupsweedout_table;
  /*
    Tables that we will need to have in the prefix to do the weedout step
    (all inner and all outer that the involved semi-joins are correlated with)
  */
  table_map dupsweedout_tables;

/* SJ-Materialization-Scan strategy */
  /* The last inner table (valid once we're after it) */
  uint      sjm_scan_last_inner;
  /*
    Tables that we need to have in the prefix to calculate the correct cost.
    Basically, we need all inner tables and outer tables mentioned in the
    semi-join's ON expression so we can correctly account for fanout.
  */
  table_map sjm_scan_need_tables;

  table_map prefix_dups_producing_tables;
} POSITION;


typedef struct st_rollup
{
  enum State { STATE_NONE, STATE_INITED, STATE_READY };
  State state;
  Item_null_result **null_items;
  Item ***ref_pointer_arrays;
  List<Item> *fields;
} ROLLUP;


#define SJ_OPT_NONE 0
#define SJ_OPT_DUPS_WEEDOUT 1
#define SJ_OPT_LOOSE_SCAN   2
#define SJ_OPT_FIRST_MATCH  3
#define SJ_OPT_MATERIALIZE  4
#define SJ_OPT_MATERIALIZE_SCAN  5

inline bool sj_is_materialize_strategy(uint strategy)
{
  return strategy >= SJ_OPT_MATERIALIZE;
}


class JOIN :public Sql_alloc
{
  JOIN(const JOIN &rhs);                        /**< not implemented */
  JOIN& operator=(const JOIN &rhs);             /**< not implemented */
public:
  JOIN_TAB *join_tab,**best_ref;
  JOIN_TAB **map2table;    ///< mapping between table indexes and JOIN_TABs
  JOIN_TAB *join_tab_save; ///< saved join_tab for subquery reexecution
  TABLE    **table;
  TABLE    **all_tables;
  /**
    The table which has an index that allows to produce the requried ordering.
    A special value of 0x1 means that the ordering will be produced by
    passing 1st non-const table to filesort(). NULL means no such table exists.
  */
  TABLE    *sort_by_table;
  uint	   tables;        /**< Number of tables in the join */
  uint     outer_tables;  /**< Number of tables that are not inside semijoin */
  uint     const_tables;
  uint	   send_group_parts;
  bool	   group;          /**< If query contains GROUP BY clause */
  /**
    Indicates that grouping will be performed on the result set during
    query execution. This field belongs to query execution.

    @see make_group_fields, alloc_group_fields, JOIN::exec
  */
  bool     sort_and_group; 
  bool     first_record,full_join, no_field_update;
  bool	   do_send_rows;
  /**
    TRUE when we want to resume nested loop iterations when
    fetching data from a cursor
  */
  bool     resume_nested_loop;
  table_map const_table_map;
  /*
    Constant tables for which we have found a row (as opposed to those for
    which we didn't).
  */
  table_map found_const_table_map;
  
  /* Tables removed by table elimination. Set to 0 before the elimination. */
  table_map eliminated_tables;
  /*
     Bitmap of all inner tables from outer joins
  */
  table_map outer_join;
  ha_rows  send_records,found_records,examined_rows,row_limit, select_limit;
  /**
    Used to fetch no more than given amount of rows per one
    fetch operation of server side cursor.
    The value is checked in end_send and end_send_group in fashion, similar
    to offset_limit_cnt:
      - fetch_limit= HA_POS_ERROR if there is no cursor.
      - when we open a cursor, we set fetch_limit to 0,
      - on each fetch iteration we add num_rows to fetch to fetch_limit
  */
  ha_rows  fetch_limit;
  /* Finally picked QEP. This is result of join optimization */
  POSITION best_positions[MAX_TABLES+1];

/******* Join optimization state members start *******/
  /*
    pointer - we're doing optimization for a semi-join materialization nest.
    NULL    - otherwise
  */
  TABLE_LIST *emb_sjm_nest;
  
  /* Current join optimization state */
  POSITION positions[MAX_TABLES+1];
  
  /*
    Bitmap of nested joins embedding the position at the end of the current 
    partial join (valid only during join optimizer run).
  */
  nested_join_map cur_embedding_map;
  
  /*
    Bitmap of inner tables of semi-join nests that have a proper subset of
    their tables in the current join prefix. That is, of those semi-join
    nests that have their tables both in and outside of the join prefix.
  */
  table_map cur_sj_inner_tables;
  
  /*
    Bitmap of semi-join inner tables that are in the join prefix and for
    which there's no provision for how to eliminate semi-join duplicates
    they produce.
  */
  table_map cur_dups_producing_tables;

  /* We also maintain a stack of join optimization states in * join->positions[] */
/******* Join optimization state members end *******/
  Next_select_func first_select;
  /*
    The cost of best complete join plan found so far during optimization,
    after optimization phase - cost of picked join order (not taking into
    account the changes made by test_if_skip_sort_order()).
  */
  double   best_read;
  List<Item> *fields;
  List<Cached_item> group_fields, group_fields_cache;
  TABLE    *tmp_table;
  /// used to store 2 possible tmp table of SELECT
  TABLE    *exec_tmp_table1, *exec_tmp_table2;
  THD	   *thd;
  Item_sum  **sum_funcs, ***sum_funcs_end;
  /** second copy of sumfuncs (for queries with 2 temporary tables */
  Item_sum  **sum_funcs2, ***sum_funcs_end2;
  Procedure *procedure;
  Item	    *having;
  Item      *tmp_having; ///< To store having when processed temporary table
  Item      *having_history; ///< Store having for explain
  ulonglong  select_options;
  /* 
    Bitmap of allowed types of the join caches that
    can be used for join operations
  */
  uint allowed_join_cache_types;
  bool allowed_semijoin_with_cache;
  bool allowed_outer_join_with_cache;
  /* Maximum level of the join caches that can be used for join operations */ 
  uint max_allowed_join_cache_level;
  select_result *result;
  TMP_TABLE_PARAM tmp_table_param;
  MYSQL_LOCK *lock;
  /// unit structure (with global parameters) for this select
  SELECT_LEX_UNIT *unit;
  /// select that processed
  SELECT_LEX *select_lex;
  /** 
    TRUE <=> optimizer must not mark any table as a constant table.
    This is needed for subqueries in form "a IN (SELECT .. UNION SELECT ..):
    when we optimize the select that reads the results of the union from a
    temporary table, we must not mark the temp. table as constant because
    the number of rows in it may vary from one subquery execution to another.
  */
  bool no_const_tables; 
  /*
    This flag is set if we call no_rows_in_result() as par of end_group().
    This is used as a simple speed optimization to avoiding calling
    restore_no_rows_in_result() in ::reinit()
  */
  bool no_rows_in_result_called;
  
  /**
    Copy of this JOIN to be used with temporary tables.

    tmp_join is used when the JOIN needs to be "reusable" (e.g. in a
    subquery that gets re-executed several times) and we know will use
    temporary tables for materialization. The materialization to a
    temporary table overwrites the JOIN structure to point to the
    temporary table after the materialization is done. This is where
    tmp_join is used : it's a copy of the JOIN before the
    materialization and is used in restoring before re-execution by
    overwriting the current JOIN structure with the saved copy.
    Because of this we should pay extra care of not freeing up helper
    structures that are referenced by the original contents of the
    JOIN. We can check for this by making sure the "current" join is
    not the temporary copy, e.g.  !tmp_join || tmp_join != join
 
    We should free these sub-structures at JOIN::destroy() if the
    "current" join has a copy is not that copy.
  */
  JOIN *tmp_join;
  ROLLUP rollup;				///< Used with rollup

  bool select_distinct;				///< Set if SELECT DISTINCT
  /**
    If we have the GROUP BY statement in the query,
    but the group_list was emptied by optimizer, this
    flag is TRUE.
    It happens when fields in the GROUP BY are from
    constant table
  */
  bool group_optimized_away;

  /*
    simple_xxxxx is set if ORDER/GROUP BY doesn't include any references
    to other tables than the first non-constant table in the JOIN.
    It's also set if ORDER/GROUP BY is empty.
    Used for deciding for or against using a temporary table to compute 
    GROUP/ORDER BY.
  */
  bool simple_order, simple_group;
  /**
    Is set only in case if we have a GROUP BY clause
    and no ORDER BY after constant elimination of 'order'.
  */
  bool no_order;
  /** Is set if we have a GROUP BY and we have ORDER BY on a constant. */
  bool          skip_sort_order;

  bool need_tmp, hidden_group_fields;
  DYNAMIC_ARRAY keyuse;
  Item::cond_result cond_value, having_value;
  List<Item> all_fields; ///< to store all fields that used in query
  ///Above list changed to use temporary table
  List<Item> tmp_all_fields1, tmp_all_fields2, tmp_all_fields3;
  ///Part, shared with list above, emulate following list
  List<Item> tmp_fields_list1, tmp_fields_list2, tmp_fields_list3;
  List<Item> &fields_list; ///< hold field list passed to mysql_select
  List<Item> procedure_fields_list;
  int error;

  ORDER *order, *group_list, *proc_param; //hold parameters of mysql_select
  COND *conds;                            // ---"---
  Item *conds_history;                    // store WHERE for explain
  COND *outer_ref_cond;       ///<part of conds containing only outer references
  TABLE_LIST *tables_list;           ///<hold 'tables' parameter of mysql_select
  List<TABLE_LIST> *join_list;       ///< list of joined tables in reverse order
  COND_EQUAL *cond_equal;
  COND_EQUAL *having_equal;
  SQL_SELECT *select;                ///<created in optimisation phase
  JOIN_TAB *return_tab;              ///<used only for outer joins
  Item **ref_pointer_array; ///<used pointer reference for this select
  // Copy of above to be used with different lists
  Item **items0, **items1, **items2, **items3, **current_ref_pointer_array;
  uint ref_pointer_array_size; ///< size of above in bytes
  const char *zero_result_cause; ///< not 0 if exec must return zero result
  
  bool union_part; ///< this subselect is part of union 
  bool optimized; ///< flag to avoid double optimization in EXPLAIN

  Array<Item_in_subselect> sj_subselects;

  /* Temporary tables used to weed-out semi-join duplicates */
  List<TABLE> sj_tmp_tables;
  /* SJM nests that are executed with SJ-Materialization strategy */
  List<SJ_MATERIALIZATION_INFO> sjm_info_list;

  /* 
    storage for caching buffers allocated during query execution. 
    These buffers allocations need to be cached as the thread memory pool is
    cleared only at the end of the execution of the whole query and not caching
    allocations that occur in repetition at execution time will result in 
    excessive memory usage.
    Note: make_simple_join always creates an execution plan that accesses
    a single table, thus it is sufficient to have a one-element array for
    table_reexec.
  */  
  SORT_FIELD *sortorder;                        // make_unireg_sortorder()
  TABLE *table_reexec[1];                       // make_simple_join()
  JOIN_TAB *join_tab_reexec;                    // make_simple_join()
  /* end of allocation caching storage */

  JOIN(THD *thd_arg, List<Item> &fields_arg, ulonglong select_options_arg,
       select_result *result_arg)
    :fields_list(fields_arg), sj_subselects(thd_arg->mem_root, 4)
  {
    init(thd_arg, fields_arg, select_options_arg, result_arg);
  }

  void init(THD *thd_arg, List<Item> &fields_arg, ulonglong select_options_arg,
       select_result *result_arg)
  {
    join_tab= join_tab_save= 0;
    table= 0;
    tables= 0;
    const_tables= 0;
    eliminated_tables= 0;
    join_list= 0;
    implicit_grouping= FALSE;
    sort_and_group= 0;
    first_record= 0;
    do_send_rows= 1;
    resume_nested_loop= FALSE;
    send_records= 0;
    found_records= 0;
    fetch_limit= HA_POS_ERROR;
    examined_rows= 0;
    exec_tmp_table1= 0;
    exec_tmp_table2= 0;
    sortorder= 0;
    table_reexec[0]= 0;
    join_tab_reexec= 0;
    thd= thd_arg;
    sum_funcs= sum_funcs2= 0;
    procedure= 0;
    having= tmp_having= having_history= 0;
    select_options= select_options_arg;
    result= result_arg;
    lock= thd_arg->lock;
    select_lex= 0; //for safety
    tmp_join= 0;
    select_distinct= test(select_options & SELECT_DISTINCT);
    no_order= 0;
    simple_order= 0;
    simple_group= 0;
    skip_sort_order= 0;
    need_tmp= 0;
    hidden_group_fields= 0; /*safety*/
    error= 0;
    select= 0;
    return_tab= 0;
    ref_pointer_array= items0= items1= items2= items3= 0;
    ref_pointer_array_size= 0;
    zero_result_cause= 0;
    optimized= 0;
    cond_equal= 0;
    having_equal= 0;
    group_optimized_away= 0;
    no_rows_in_result_called= 0;

    all_fields= fields_arg;
    if (&fields_list != &fields_arg)      /* Avoid valgrind-warning */
      fields_list= fields_arg;
    bzero((char*) &keyuse,sizeof(keyuse));
    tmp_table_param.init();
    tmp_table_param.end_write_records= HA_POS_ERROR;
    rollup.state= ROLLUP::STATE_NONE;

    no_const_tables= FALSE;
    first_select= sub_select;
    outer_ref_cond= 0;
  }

  int prepare(Item ***rref_pointer_array, TABLE_LIST *tables, uint wind_num,
	      COND *conds, uint og_num, ORDER *order, ORDER *group,
	      Item *having, ORDER *proc_param, SELECT_LEX *select,
	      SELECT_LEX_UNIT *unit);
  int optimize();
  int reinit();
  void exec();
  int destroy();
  void restore_tmp();
  bool alloc_func_list();
  bool flatten_subqueries();
  bool setup_subquery_materialization();
  bool make_sum_func_list(List<Item> &all_fields, List<Item> &send_fields,
			  bool before_group_by, bool recompute= FALSE);

  inline void set_items_ref_array(Item **ptr)
  {
    memcpy((char*) ref_pointer_array, (char*) ptr, ref_pointer_array_size);
    current_ref_pointer_array= ptr;
  }
  inline void init_items_ref_array()
  {
    items0= ref_pointer_array + all_fields.elements;
    memcpy(items0, ref_pointer_array, ref_pointer_array_size);
    current_ref_pointer_array= items0;
  }

  bool rollup_init();
  bool rollup_process_const_fields();
  bool rollup_make_fields(List<Item> &all_fields, List<Item> &fields,
			  Item_sum ***func);
  int rollup_send_data(uint idx);
  int rollup_write_data(uint idx, TABLE *table);
  /**
    Release memory and, if possible, the open tables held by this execution
    plan (and nested plans). It's used to release some tables before
    the end of execution in order to increase concurrency and reduce
    memory consumption.
  */
  void join_free();
  /** Cleanup this JOIN, possibly for reuse */
  void cleanup(bool full);
  void clear();
  bool save_join_tab();
  bool init_save_join_tab();
  bool send_row_on_empty_set()
  {
    return (do_send_rows && implicit_grouping &&
            having_value != Item::COND_FALSE);
  }
  bool change_result(select_result *result);
  bool is_top_level_join() const
  {
    return (unit == &thd->lex->unit && (unit->fake_select_lex == 0 ||
                                        select_lex == unit->fake_select_lex));
  }
  inline table_map all_tables_map()
  {
    return (table_map(1) << tables) - 1;
  }
  /* 
    Return the table for which an index scan can be used to satisfy 
    the sort order needed by the ORDER BY/(implicit) GROUP BY clause 
  */
  JOIN_TAB *get_sort_by_join_tab()
  {
    return (need_tmp || !sort_by_table || skip_sort_order ||
            ((group || tmp_table_param.sum_func_count) && !group_list)) ?
              NULL : join_tab+const_tables;
  }
  bool setup_subquery_caches();
  bool shrink_join_buffers(JOIN_TAB *jt, 
                           ulonglong curr_space,
                           ulonglong needed_space);
  void set_allowed_join_cache_types();
  bool is_allowed_hash_join_access()
  { 
    return test(allowed_join_cache_types & JOIN_CACHE_HASHED_BIT) &&
           max_allowed_join_cache_level > JOIN_CACHE_HASHED_BIT;
  }

private:
  /**
    TRUE if the query contains an aggregate function but has no GROUP
    BY clause. 
  */
  bool implicit_grouping; 
  bool make_simple_join(JOIN *join, TABLE *tmp_table);
  void cleanup_item_list(List<Item> &items) const;
};


typedef struct st_select_check {
  uint const_ref,reg_ref;
} SELECT_CHECK;

extern const char *join_type_str[];
void TEST_join(JOIN *join);

/* Extern functions in sql_select.cc */
bool store_val_in_field(Field *field, Item *val, enum_check_fields check_flag);
void count_field_types(SELECT_LEX *select_lex, TMP_TABLE_PARAM *param, 
                       List<Item> &fields, bool reset_with_sum_func);
bool setup_copy_fields(THD *thd, TMP_TABLE_PARAM *param,
		       Item **ref_pointer_array,
		       List<Item> &new_list1, List<Item> &new_list2,
		       uint elements, List<Item> &fields);
void copy_fields(TMP_TABLE_PARAM *param);
bool copy_funcs(Item **func_ptr, const THD *thd);
bool create_internal_tmp_table_from_heap(THD *thd, TABLE *table, TMP_TABLE_PARAM *param,
			     int error, bool ignore_last_dupp_error);
uint find_shortest_key(TABLE *table, const key_map *usable_keys);
Field* create_tmp_field_from_field(THD *thd, Field* org_field,
                                   const char *name, TABLE *table,
                                   Item_field *item, uint convert_blob_length);
                                                                      
/* functions from opt_sum.cc */
bool simple_pred(Item_func *func_item, Item **args, bool *inv_order);
int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds);

/* from sql_delete.cc, used by opt_range.cc */
extern "C" int refpos_order_cmp(void* arg, const void *a,const void *b);

/** class to copying an field/item to a key struct */

class store_key :public Sql_alloc
{
public:
  bool null_key; /* TRUE <=> the value of the key has a null part */
  enum store_key_result { STORE_KEY_OK, STORE_KEY_FATAL, STORE_KEY_CONV };
  enum Type { FIELD_STORE_KEY, ITEM_STORE_KEY, CONST_ITEM_STORE_KEY };
  store_key(THD *thd, Field *field_arg, uchar *ptr, uchar *null, uint length)
    :null_key(0), null_ptr(null), err(0)
  {
    if (field_arg->type() == MYSQL_TYPE_BLOB
        || field_arg->type() == MYSQL_TYPE_GEOMETRY)
    {
      /* 
        Key segments are always packed with a 2 byte length prefix.
        See mi_rkey for details.
      */
      to_field= new Field_varstring(ptr, length, 2, null, 1, 
                                    Field::NONE, field_arg->field_name,
                                    field_arg->table->s, field_arg->charset());
      to_field->init(field_arg->table);
    }
    else
      to_field=field_arg->new_key_field(thd->mem_root, field_arg->table,
                                        ptr, null, 1);
  }
  virtual ~store_key() {}			/** Not actually needed */
  virtual enum Type type() const=0;
  virtual const char *name() const=0;

  /**
    @brief sets ignore truncation warnings mode and calls the real copy method

    @details this function makes sure truncation warnings when preparing the
    key buffers don't end up as errors (because of an enclosing INSERT/UPDATE).
  */
  enum store_key_result copy()
  {
    enum store_key_result result;
    THD *thd= to_field->table->in_use;
    enum_check_fields saved_count_cuted_fields= thd->count_cuted_fields;
    ulong sql_mode= thd->variables.sql_mode;
    thd->variables.sql_mode&= ~(MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE);

    thd->count_cuted_fields= CHECK_FIELD_IGNORE;

    result= copy_inner();

    thd->count_cuted_fields= saved_count_cuted_fields;
    thd->variables.sql_mode= sql_mode;

    return result;
  }

 protected:
  Field *to_field;				// Store data here
  uchar *null_ptr;
  uchar err;

  virtual enum store_key_result copy_inner()=0;
};


class store_key_field: public store_key
{
  Copy_field copy_field;
  const char *field_name;
 public:
  store_key_field(THD *thd, Field *to_field_arg, uchar *ptr,
                  uchar *null_ptr_arg,
		  uint length, Field *from_field, const char *name_arg)
    :store_key(thd, to_field_arg,ptr,
	       null_ptr_arg ? null_ptr_arg : from_field->maybe_null() ? &err
	       : (uchar*) 0, length), field_name(name_arg)
  {
    if (to_field)
    {
      copy_field.set(to_field,from_field,0);
    }
  }  

  enum Type type() const { return FIELD_STORE_KEY; }
  const char *name() const { return field_name; }

  void change_source_field(Item_field *fld_item)
  {
    copy_field.set(to_field, fld_item->field, 0);
    field_name= fld_item->full_name();
  }

 protected: 
  enum store_key_result copy_inner()
  {
    TABLE *table= copy_field.to_field->table;
    my_bitmap_map *old_map= dbug_tmp_use_all_columns(table,
                                                     table->write_set);

    /* 
      It looks like the next statement is needed only for a simplified
      hash function over key values used now in BNLH join.
      When the implementation of this function will be replaced for a proper
      full version this statement probably should be removed.
    */  
    bzero(copy_field.to_ptr,copy_field.to_length);

    copy_field.do_copy(&copy_field);
    dbug_tmp_restore_column_map(table->write_set, old_map);
    null_key= to_field->is_null();
    return err != 0 ? STORE_KEY_FATAL : STORE_KEY_OK;
  }
};


class store_key_item :public store_key
{
 protected:
  Item *item;
  /*
    Flag that forces usage of save_val() method which save value of the
    item instead of save_in_field() method which saves result.
  */
  bool use_value;
public:
  store_key_item(THD *thd, Field *to_field_arg, uchar *ptr,
                 uchar *null_ptr_arg, uint length, Item *item_arg, bool val)
    :store_key(thd, to_field_arg, ptr,
	       null_ptr_arg ? null_ptr_arg : item_arg->maybe_null ?
	       &err : (uchar*) 0, length), item(item_arg), use_value(val)
  {}

  enum Type type() const { return ITEM_STORE_KEY; }
  const char *name() const { return "func"; }

 protected:  
  enum store_key_result copy_inner()
  {
    TABLE *table= to_field->table;
    my_bitmap_map *old_map= dbug_tmp_use_all_columns(table,
                                                     table->write_set);
    int res= FALSE;

    /* 
      It looks like the next statement is needed only for a simplified
      hash function over key values used now in BNLH join.
      When the implementation of this function will be replaced for a proper
      full version this statement probably should be removed.
    */  
    to_field->reset();

    if (use_value)
      item->save_val(to_field);
    else
      res= item->save_in_field(to_field, 1);
    /*
     Item::save_in_field() may call Item::val_xxx(). And if this is a subquery
     we need to check for errors executing it and react accordingly
    */
    if (!res && table->in_use->is_error())
      res= 1; /* STORE_KEY_FATAL */
    dbug_tmp_restore_column_map(table->write_set, old_map);
    null_key= to_field->is_null() || item->null_value;
    return ((err != 0 || res < 0 || res > 2) ? STORE_KEY_FATAL : 
            (store_key_result) res);
  }
};


class store_key_const_item :public store_key_item
{
  bool inited;
public:
  store_key_const_item(THD *thd, Field *to_field_arg, uchar *ptr,
		       uchar *null_ptr_arg, uint length,
		       Item *item_arg)
    :store_key_item(thd, to_field_arg,ptr,
		    null_ptr_arg ? null_ptr_arg : item_arg->maybe_null ?
		    &err : (uchar*) 0, length, item_arg, FALSE), inited(0)
  {
  }

  enum Type type() const { return CONST_ITEM_STORE_KEY; }
  const char *name() const { return "const"; }

protected:  
  enum store_key_result copy_inner()
  {
    int res;
    if (!inited)
    {
      inited=1;
      if ((res= item->save_in_field(to_field, 1)))
      {       
        if (!err)
          err= res < 0 ? 1 : res; /* 1=STORE_KEY_FATAL */
      }
      /*
        Item::save_in_field() may call Item::val_xxx(). And if this is a subquery
        we need to check for errors executing it and react accordingly
        */
      if (!err && to_field->table->in_use->is_error())
        err= 1; /* STORE_KEY_FATAL */
    }
    null_key= to_field->is_null() || item->null_value;
    return (err > 2 ? STORE_KEY_FATAL : (store_key_result) err);
  }
};

bool cp_buffer_from_ref(THD *thd, TABLE *table, TABLE_REF *ref);
bool error_if_full_join(JOIN *join);
int report_error(TABLE *table, int error);
int safe_index_read(JOIN_TAB *tab);
COND *remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value);
int test_if_item_cache_changed(List<Cached_item> &list);
int join_init_read_record(JOIN_TAB *tab);
void set_position(JOIN *join,uint idx,JOIN_TAB *table,KEYUSE *key);
inline Item * and_items(Item* cond, Item *item)
{
  return (cond? (new Item_cond_and(cond, item)) : item);
}
bool choose_plan(JOIN *join,table_map join_tables);
void get_partial_join_cost(JOIN *join, uint n_tables, double *read_time_arg,
                           double *record_count_arg);
void optimize_wo_join_buffering(JOIN *join, uint first_tab, uint last_tab, 
                                table_map last_remaining_tables, 
                                bool first_alt, uint no_jbuf_before,
                                double *outer_rec_count, double *reopt_cost);
Item_equal *find_item_equal(COND_EQUAL *cond_equal, Field *field,
                            bool *inherited_fl);
bool test_if_ref(COND *root_cond, 
                 Item_field *left_item,Item *right_item);

inline bool optimizer_flag(THD *thd, uint flag)
{ 
  return (thd->variables.optimizer_switch & flag);
}

/* Table elimination entry point function */
void eliminate_tables(JOIN *join);

/* Index Condition Pushdown entry point function */
void push_index_cond(JOIN_TAB *tab, uint keyno);

/****************************************************************************
  Temporary table support for SQL Runtime
 ***************************************************************************/

#define STRING_TOTAL_LENGTH_TO_PACK_ROWS 128
#define AVG_STRING_LENGTH_TO_PACK_ROWS   64
#define RATIO_TO_PACK_ROWS	       2
#define MIN_STRING_LENGTH_TO_PACK_ROWS   10

TABLE *create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
			ORDER *group, bool distinct, bool save_sum_fields,
			ulonglong select_options, ha_rows rows_limit,
			char* alias);
void free_tmp_table(THD *thd, TABLE *entry);
bool create_internal_tmp_table_from_heap(THD *thd, TABLE *table,
                                         ENGINE_COLUMNDEF *start_recinfo,
                                         ENGINE_COLUMNDEF **recinfo, 
                                         int error, bool ignore_last_dupp_key_error);
bool create_internal_tmp_table(TABLE *table, KEY *keyinfo, 
                               ENGINE_COLUMNDEF *start_recinfo,
                               ENGINE_COLUMNDEF **recinfo, 
                               ulonglong options);
bool open_tmp_table(TABLE *table);
void setup_tmp_table_column_bitmaps(TABLE *table, uchar *bitmaps);

#endif /* SQL_SELECT_INCLUDED */