mariadb/sql/sql_select.h

/* Copyright (C) 2000-2006 MySQL AB

   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_MARIA_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

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;
} KEYUSE;

class store_key;

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;
  /*
    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};

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 */
  SQL_SELECT	*select;
  COND		*select_cond;
  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;
  bool          use_join_cache;
  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;

  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;
  }
  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; }
} JOIN_TAB;


/* 
  Categories of data fields of variable length written into join cache buffers.
  The value of any of these fields is written into cache together with the
  prepended length of the value.     
*/
#define CACHE_BLOB      1        /* blob field  */
#define CACHE_STRIPPED  2        /* field stripped of trailing spaces */
#define CACHE_VARSTR1   3        /* short string value (length takes 1 byte) */ 
#define CACHE_VARSTR2   4        /* long string value (length takes 2 bytes) */

/*
  The CACHE_FIELD structure used to describe fields of records that
  are written into a join cache buffer from record buffers and backward.
*/
typedef struct st_cache_field {
  uchar *str;   /**< buffer from/to where the field is to be copied */ 
  uint length;  /**< maximal number of bytes to be copied from/to str */
  /* 
    Field object for the moved field
    (0 - for a flag field, see JOIN_CACHE::create_flag_fields).
  */
  Field *field;
  uint type;    /**< category of the of the copied field (CACHE_BLOB et al.) */
  /* 
    The number of the record offset value for the field in the sequence
    of offsets placed after the last field of the record. These
    offset values are used to access fields referred to from other caches.
    If the value is 0 then no offset for the field is saved in the
    trailing sequence of offsets.
  */ 
  uint referenced_field_no; 
  /* The remaining structure fields are used as containers for temp values */
  uint blob_length; /**< length of the blob to be copied */
  uint offset;      /**< field offset to be saved in cache buffer */
} CACHE_FIELD;


class JOIN_TAB_SCAN;


/*
  JOIN_CACHE is the base class to support the implementations of 
  - Block Nested Loop (BNL) Join Algorithm,
  - Block Nested Loop Hash (BNLH) Join Algorithm,
  - Batched Key Access (BKA) Join Algorithm.
  The first algorithm is supported by the derived class JOIN_CACHE_BNL,
  the second algorithm is supported by the derived class JOIN_CACHE_BNLH,
  while the third algorithm is implemented in two variant supported by
  the classes JOIN_CACHE_BKA and JOIN_CACHE_BKAH.
  These three algorithms have a lot in common. Each of them first accumulates
  the records of the left join operand in a join buffer and then searches for
  matching rows of the second operand for all accumulated records.
  For the first two algorithms this strategy saves on logical I/O operations:
  the entire set of records from the join buffer requires only one look-through
  of the records provided by the second operand. 
  For the third algorithm the accumulation of records allows to optimize
  fetching rows of the second operand from disk for some engines (MyISAM, 
  InnoDB), or to minimize the number of round-trips between the Server and
  the engine nodes (NDB Cluster).        
*/ 

class JOIN_CACHE :public Sql_alloc
{

private:

  /* Size of the offset of a record from the cache */   
  uint size_of_rec_ofs;    
  /* Size of the length of a record in the cache */
  uint size_of_rec_len;
  /* Size of the offset of a field within a record in the cache */   
  uint size_of_fld_ofs;

protected:
       
  /* 3 functions below actually do not use the hidden parameter 'this' */ 

  /* Calculate the number of bytes used to store an offset value */
  uint offset_size(uint len)
  { return (len < 256 ? 1 : len < 256*256 ? 2 : 4); }

  /* Get the offset value that takes ofs_sz bytes at the position ptr */
  ulong get_offset(uint ofs_sz, uchar *ptr)
  {
    switch (ofs_sz) {
    case 1: return uint(*ptr);
    case 2: return uint2korr(ptr);
    case 4: return uint4korr(ptr);
    }
    return 0;
  }

  /* Set the offset value ofs that takes ofs_sz bytes at the position ptr */ 
  void store_offset(uint ofs_sz, uchar *ptr, ulong ofs)
  {
    switch (ofs_sz) {
    case 1: *ptr= (uchar) ofs; return;
    case 2: int2store(ptr, (uint16) ofs); return;
    case 4: int4store(ptr, (uint32) ofs); return;
    }
  }
  
  /* 
    The maximum total length of the fields stored for a record in the cache.
    For blob fields only the sizes of the blob lengths are taken into account. 
  */
  uint length;

  /* 
    Representation of the executed multi-way join through which all needed
    context can be accessed.  
  */   
  JOIN *join;  

  /* 
    Cardinality of the range of join tables whose fields can be put into the
    cache. A table from the range not necessarily contributes to the cache.
  */
  uint tables;

  /* 
    The total number of flag and data fields that can appear in a record
    written into the cache. Fields with null values are always skipped 
    to save space. 
  */
  uint fields;

  /* 
    The total number of flag fields in a record put into the cache. They are
    used for table null bitmaps, table null row flags, and an optional match
    flag. Flag fields go before other fields in a cache record with the match
    flag field placed always at the very beginning of the record.
  */
  uint flag_fields;

  /* The total number of blob fields that are written into the cache */ 
  uint blobs;

  /* 
    The total number of fields referenced from field descriptors for other join
    caches. These fields are used to construct key values.
    When BKA join algorithm is employed the constructed key values serve to
    access matching rows with index lookups.
    The key values are put into a hash table when the BNLH join algorithm
    is employed and when BKAH is used for the join operation. 
  */   
  uint referenced_fields;
   
  /* 
    The current number of already created data field descriptors.
    This number can be useful for implementations of the init methods.  
  */
  uint data_field_count; 

  /* 
    The current number of already created pointers to the data field
    descriptors. This number can be useful for implementations of
    the init methods.  
  */
  uint data_field_ptr_count;
 
  /* 
    Array of the descriptors of fields containing 'fields' elements.
    These are all fields that are stored for a record in the cache. 
  */
  CACHE_FIELD *field_descr;

  /* 
    Array of pointers to the blob descriptors that contains 'blobs' elements.
  */
  CACHE_FIELD **blob_ptr;

  /* 
    This flag indicates that records written into the join buffer contain
    a match flag field. The flag must be set by the init method. 
  */
  bool with_match_flag; 
  /*
    This flag indicates that any record is prepended with the length of the
    record which allows us to skip the record or part of it without reading.
  */
  bool with_length;

  /* 
    The maximal number of bytes used for a record representation in
    the cache excluding the space for blob data. 
    For future derived classes this representation may contains some
    redundant info such as a key value associated with the record.     
  */
  uint pack_length;
  /* 
    The value of pack_length incremented by the total size of all 
    pointers of a record in the cache to the blob data. 
  */
  uint pack_length_with_blob_ptrs;

  /* 
    The total size of the record base prefix. The base prefix of record may
    include the following components:
     - the length of the record
     - the link to a record in a previous buffer.
    Each record in the buffer are supplied with the same set of the components.
  */
  uint base_prefix_length;

  /*
    The expected length of a record in the join buffer together with     
    all prefixes and postfixes
  */
  ulong avg_record_length;

  /* The expected size of the space per record in the auxiliary buffer */
  ulong avg_aux_buffer_incr;

  /* Expected join buffer space used for one record */
  ulong space_per_record; 

  /* Pointer to the beginning of the join buffer */
  uchar *buff;         
  /* 
    Size of the entire memory allocated for the join buffer.
    Part of this memory may be reserved for the auxiliary buffer.
  */ 
  ulong buff_size;
  /* The minimal join buffer size when join buffer still makes sense to use */
  ulong min_buff_size;
  /* The maximum expected size if the join buffer to be used */
  ulong max_buff_size;
  /* Size of the auxiliary buffer */ 
  ulong aux_buff_size;

  /* The number of records put into the join buffer */ 
  ulong records;
  /* 
    The number of records in the fully refilled join buffer of
    the minimal size equal to min_buff_size
  */
  ulong min_records;
  /*
    The maximum expected number of records to be put in the join buffer
    at one refill 
  */
  ulong max_records;

  /* 
    Pointer to the current position in the join buffer.
    This member is used both when writing to buffer and
    when reading from it.
  */
  uchar *pos;
  /* 
    Pointer to the first free position in the join buffer,
    right after the last record into it.
  */
  uchar *end_pos; 

  /* 
    Pointer to the beginning of the first field of the current read/write
    record from the join buffer. The value is adjusted by the 
    get_record/put_record functions.
  */
  uchar *curr_rec_pos;
  /* 
    Pointer to the beginning of the first field of the last record
    from the join buffer.
  */
  uchar *last_rec_pos;

  /* 
    Flag is set if the blob data for the last record in the join buffer
    is in record buffers rather than in the join cache.
  */
  bool last_rec_blob_data_is_in_rec_buff;

  /* 
    Pointer to the position to the current record link. 
    Record links are used only with linked caches. Record links allow to set
    connections between parts of one join record that are stored in different
    join buffers.
    In the simplest case a record link is just a pointer to the beginning of
    the record stored in the buffer.
    In a more general case a link could be a reference to an array of pointers
    to records in the buffer.
  */
  uchar *curr_rec_link;

  /*
    The number of fields put in the join buffer of the join cache that are
    used in building keys to access the table join_tab
  */
  uint local_key_arg_fields;
  /* 
    The total number of the fields in the previous caches that are used
    in building keys to access the table join_tab
  */
  uint external_key_arg_fields;

  /* 
    This flag indicates that the key values will be read directly from the join
    buffer. It will save us building key values in the key buffer.
  */
  bool use_emb_key;
  /* The length of an embedded key value */ 
  uint emb_key_length;

  /*
    This object provides the methods to iterate over records of
    the joined table join_tab when looking for join matches between
    records from join buffer and records from join_tab.
    BNL and BNLH join algorithms retrieve all records from join_tab,
    while BKA/BKAH algorithm iterates only over those records from
    join_tab that can be accessed by look-ups with join keys built
    from records in join buffer.  
  */
  JOIN_TAB_SCAN *join_tab_scan;

  void calc_record_fields();     
  void collect_info_on_key_args();
  int alloc_fields();
  void create_flag_fields();
  void create_key_arg_fields();
  void create_remaining_fields();
  void set_constants();
  int alloc_buffer();

  /* Shall reallocate the join buffer */
  virtual int realloc_buffer();
  
  /* Check the possibility to read the access keys directly from join buffer */ 
  bool check_emb_key_usage();

  uint get_size_of_rec_offset() { return size_of_rec_ofs; }
  uint get_size_of_rec_length() { return size_of_rec_len; }
  uint get_size_of_fld_offset() { return size_of_fld_ofs; }

  uchar *get_rec_ref(uchar *ptr)
  {
    return buff+get_offset(size_of_rec_ofs, ptr-size_of_rec_ofs);
  }
  ulong get_rec_length(uchar *ptr)
  { 
    return (ulong) get_offset(size_of_rec_len, ptr);
  }
  ulong get_fld_offset(uchar *ptr)
  { 
    return (ulong) get_offset(size_of_fld_ofs, ptr);
  }

  void store_rec_ref(uchar *ptr, uchar* ref)
  {
    store_offset(size_of_rec_ofs, ptr-size_of_rec_ofs, (ulong) (ref-buff));
  }
  void store_rec_length(uchar *ptr, ulong len)
  {
    store_offset(size_of_rec_len, ptr, len);
  }
  void store_fld_offset(uchar *ptr, ulong ofs)
  {
    store_offset(size_of_fld_ofs, ptr, ofs);
  }

  /* Write record fields and their required offsets into the join buffer */ 
  uint write_record_data(uchar *link, bool *is_full);

  /* Get the total length of all prefixes of a record in the join buffer */ 
  virtual uint get_prefix_length() { return base_prefix_length; }
  /* Get maximum total length of all affixes of a record in the join buffer */
  virtual uint get_record_max_affix_length(); 

  /* 
    Shall get maximum size of the additional space per record used for
    record keys
  */
  virtual uint get_max_key_addon_space_per_record() { return 0; }

  /* 
    This method must determine for how much the auxiliary buffer should be
    incremented when a new record is added to the join buffer.
    If no auxiliary buffer is needed the function should return 0.
  */
  virtual uint aux_buffer_incr(ulong recno);

  /* Shall calculate how much space is remaining in the join buffer */ 
  virtual ulong rem_space() 
  { 
    return max(buff_size-(end_pos-buff)-aux_buff_size,0);
  }

  /*  Read all flag and data fields of a record from the join buffer */
  uint read_all_record_fields();
  
  /* Read all flag fields of a record from the join buffer */
  uint read_flag_fields();

  /* Read a data record field from the join buffer */
  uint read_record_field(CACHE_FIELD *copy, bool last_record);

  /* Read a referenced field from the join buffer */
  bool read_referenced_field(CACHE_FIELD *copy, uchar *rec_ptr, uint *len);

  /* Shall skip record from the join buffer if its match flag is on */
  virtual bool skip_recurrent_match();

  /* 
    True if rec_ptr points to the record whose blob data stay in
    record buffers
  */
  bool blob_data_is_in_rec_buff(uchar *rec_ptr)
  {
    return rec_ptr == last_rec_pos && last_rec_blob_data_is_in_rec_buff;
  }

  /* Find matches from the next table for records from the join buffer */
  virtual enum_nested_loop_state join_matching_records(bool skip_last);

  /* Shall set an auxiliary buffer up (currently used only by BKA joins) */
  virtual int setup_aux_buffer(HANDLER_BUFFER &aux_buff) 
  {
    DBUG_ASSERT(0);
    return 0;
  }

  /*
    Shall get the number of ranges in the cache buffer passed
    to the MRR interface
  */  
  virtual uint get_number_of_ranges_for_mrr() { return 0; };

  /* 
    Shall prepare to look for records from the join cache buffer that would
    match the record of the joined table read into the record buffer
  */ 
  virtual bool prepare_look_for_matches(bool skip_last)= 0;
  /* 
    Shall return a pointer to the record from join buffer that is checked
    as the next candidate for a match with the current record from join_tab.
    Each implementation of this virtual function should bare in mind
    that the record position it returns shall be exactly the position
    passed as the parameter to the implementations of the virtual functions 
    skip_next_candidate_for_match and read_next_candidate_for_match.
  */   
  virtual uchar *get_next_candidate_for_match()= 0;
  /*
    Shall check whether the given record from the join buffer has its match
    flag set on and, if so, skip the record in the buffer.
  */
  virtual bool skip_recurrent_candidate_for_match(uchar *rec_ptr)= 0;
  /*
    Shall read the given record from the join buffer into the
    the corresponding record buffer
  */
  virtual void read_next_candidate_for_match(uchar *rec_ptr)= 0;

  /* 
    Shall return the location of the association label returned by 
    the multi_read_range_next function for the current record loaded
    into join_tab's record buffer
  */
  virtual uchar **get_curr_association_ptr() { return 0; };

  /* Add null complements for unmatched outer records from the join buffer */
  virtual enum_nested_loop_state join_null_complements(bool skip_last);

  /* Restore the fields of the last record from the join buffer */
  virtual void restore_last_record();

  /* Set match flag for a record in join buffer if it has not been set yet */
  bool set_match_flag_if_none(JOIN_TAB *first_inner, uchar *rec_ptr);

  enum_nested_loop_state generate_full_extensions(uchar *rec_ptr);

  /* Check matching to a partial join record from the join buffer */
  bool check_match(uchar *rec_ptr);

public:

  /* Table to be joined with the partial join records from the cache */ 
  JOIN_TAB *join_tab;

  /* Pointer to the previous join cache if there is any */
  JOIN_CACHE *prev_cache;
  /* Pointer to the next join cache if there is any */
  JOIN_CACHE *next_cache;

  /* Shall initialize the join cache structure */ 
  virtual int init();

  /* Get the current size of the cache join buffer */ 
  ulong get_join_buffer_size() { return buff_size; }
  /* Set the size of the cache join buffer to a new value */
  void set_join_buffer_size(ulong sz) { buff_size= sz; }

  /* Get the minimum possible size of the cache join buffer */
  virtual ulong get_min_join_buffer_size();
  /* Get the maximum possible size of the cache join buffer */ 
  virtual ulong get_max_join_buffer_size();

  /* Shrink the size if the cache join buffer in a given ratio */
  bool shrink_join_buffer_in_ratio(ulonglong n, ulonglong d);

  /* 
    The function shall return TRUE only when there is a key access
    to the join table
  */
  virtual bool is_key_access()= 0;

  /* Shall reset the join buffer for reading/writing */
  virtual void reset(bool for_writing);

  /* 
    This function shall add a record into the join buffer and return TRUE
    if it has been decided that it should be the last record in the buffer.
  */ 
  virtual bool put_record();

  /* 
    This function shall read the next record into the join buffer and return
    TRUE if there is no more next records.
  */ 
  virtual bool get_record();

  /* 
    This function shall read the record at the position rec_ptr
    in the join buffer
  */ 
  virtual void get_record_by_pos(uchar *rec_ptr);

  /* Shall return the value of the match flag for the positioned record */
  virtual bool get_match_flag_by_pos(uchar *rec_ptr);

  /* Shall return the position of the current record */
  virtual uchar *get_curr_rec() { return curr_rec_pos; }

  /* Shall set the current record link */
  virtual void set_curr_rec_link(uchar *link) { curr_rec_link= link; }

  /* Shall return the current record link */
  virtual uchar *get_curr_rec_link()
  { 
    return (curr_rec_link ? curr_rec_link : get_curr_rec());
  }
     
  /* Join records from the join buffer with records from the next join table */ 
  enum_nested_loop_state join_records(bool skip_last);

  virtual ~JOIN_CACHE() {}
  void reset_join(JOIN *j) { join= j; }
  void free()
  { 
    x_free(buff);
    buff= 0;
  }   
  
  friend class JOIN_CACHE_HASHED;
  friend class JOIN_CACHE_BNL;
  friend class JOIN_CACHE_BKA;
  friend class JOIN_TAB_SCAN;
  friend class JOIN_TAB_SCAN_MRR;

};


/*
  The class JOIN_CACHE_HASHED is the base class for the classes
  JOIN_CACHE_HASHED_BNL and JOIN_CACHE_HASHED_BKA. The first of them supports
  an implementation of Block Nested Loop Hash (BNLH) Join Algorithm,
  while the second is used for a variant of the BKA Join algorithm that performs
  only one lookup for any records from join buffer with the same key value. 
  For a join cache of this class the records from the join buffer that have
  the same access key are linked into a chain attached to a key entry structure
  that either itself contains the key value, or, in the case when the keys are
  embedded, refers to its occurrence in one of the records from the chain.
  To build the chains with the same keys a hash table is employed. It is placed
  at the very end of the join buffer. The array of hash entries is allocated
  first at the very bottom of the join buffer, while key entries are placed
  before this array.
  A hash entry contains a header of the list of the key entries with the same
  hash value. 
  Each key entry is a structure of the following type:
    struct st_join_cache_key_entry {
      union { 
        uchar[] value;
        cache_ref *value_ref; // offset from the beginning of the buffer
      } hash_table_key;
      key_ref next_key; // offset backward from the beginning of hash table
      cache_ref *last_rec // offset from the beginning of the buffer
    }
  The references linking the records in a chain are always placed at the very
  beginning of the record info stored in the join buffer. The records are 
  linked in a circular list. A new record is always added to the end of this 
  list.

  The following picture represents a typical layout for the info stored in the
  join buffer of a join cache object of the JOIN_CACHE_HASHED class.
    
  buff
  V
  +----------------------------------------------------------------------------+
  |     |[*]record_1_1|                                                        |
  |     ^ |                                                                    |
  |     | +--------------------------------------------------+                 |
  |     |                           |[*]record_2_1|          |                 |
  |     |                           ^ |                      V                 |
  |     |                           | +------------------+   |[*]record_1_2|   |
  |     |                           +--------------------+-+   |               |
  |+--+ +---------------------+                          | |   +-------------+ |
  ||  |                       |                          V |                 | |
  |||[*]record_3_1|         |[*]record_1_3|              |[*]record_2_2|     | |
  ||^                       ^                            ^                   | |
  ||+----------+            |                            |                   | |
  ||^          |            |<---------------------------+-------------------+ |
  |++          | | ... mrr  |   buffer ...           ... |     |               |
  |            |            |                            |                     |
  |      +-----+--------+   |                      +-----|-------+             |
  |      V     |        |   |                      V     |       |             |
  ||key_3|[/]|[*]|      |   |                |key_2|[/]|[*]|     |             |
  |                   +-+---|-----------------------+            |             |
  |                   V |   |                       |            |             |
  |             |key_1|[*]|[*]|         |   | ... |[*]|   ...  |[*]|  ...  |   |
  +----------------------------------------------------------------------------+
                                        ^           ^            ^
                                        |           i-th entry   j-th entry
                                        hash table

  i-th hash entry:
    circular record chain for key_1:
      record_1_1
      record_1_2
      record_1_3 (points to record_1_1)
    circular record chain for key_3:
      record_3_1 (points to itself)

  j-th hash entry:
    circular record chain for key_2:
      record_2_1
      record_2_2 (points to record_2_1)

*/

class JOIN_CACHE_HASHED: public JOIN_CACHE
{

private:

  /* Size of the offset of a key entry in the hash table */
  uint size_of_key_ofs;

  /* 
    Length of a key value.
    It is assumed that all key values have the same length.
  */
  uint key_length;
  /* 
    Length of the key entry in the hash table.
    A key entry either contains the key value, or it contains a reference
    to the key value if use_emb_key flag is set for the cache.
  */ 
  uint key_entry_length;
 
  /* The beginning of the hash table in the join buffer */
  uchar *hash_table;
  /* Number of hash entries in the hash table */
  uint hash_entries;


  /* The position of the currently retrieved key entry in the hash table */
  uchar *curr_key_entry;

  /* The offset of the data fields from the beginning of the record fields */
  uint data_fields_offset;
  
  uint get_hash_idx(uchar* key, uint key_len);

  int init_hash_table();
  void cleanup_hash_table();
  
protected:

  /* Number of key entries in the hash table (number of distinct keys) */
  uint key_entries;

  /* The position of the last key entry in the hash table */
  uchar *last_key_entry;

  /* 
    The offset of the record fields from the beginning of the record
    representation. The record representation starts with a reference to
    the next record in the key record chain followed by the length of
    the trailing record data followed by a reference to the record segment
    in the previous cache, if any, followed by the record fields.
  */ 
  uint rec_fields_offset;

  uint get_size_of_key_offset() { return size_of_key_ofs; }

  /* 
    Get the position of the next_key_ptr field pointed to by 
    a linking reference stored at the position key_ref_ptr. 
    This reference is actually the offset backward from the
    beginning of hash table.
  */  
  uchar *get_next_key_ref(uchar *key_ref_ptr)
  {
    return hash_table-get_offset(size_of_key_ofs, key_ref_ptr);
  }

  /* 
    Store the linking reference to the next_key_ptr field at 
    the position key_ref_ptr. The position of the next_key_ptr
    field is pointed to by ref. The stored reference is actually
    the offset backward from the beginning of the hash table.
  */  
  void store_next_key_ref(uchar *key_ref_ptr, uchar *ref)
  {
    store_offset(size_of_key_ofs, key_ref_ptr, (ulong) (hash_table-ref));
  }     
  
  /* 
    Check whether the reference to the next_key_ptr field at the position
    key_ref_ptr contains  a nil value.
  */
  bool is_null_key_ref(uchar *key_ref_ptr)
  {
    ulong nil= 0;
    return memcmp(key_ref_ptr, &nil, size_of_key_ofs ) == 0;
  } 

  /* 
    Set the reference to the next_key_ptr field at the position
    key_ref_ptr equal to nil.
  */
  void store_null_key_ref(uchar *key_ref_ptr)
  {
    ulong nil= 0;
    store_offset(size_of_key_ofs, key_ref_ptr, nil);
  } 

  uchar *get_next_rec_ref(uchar *ref_ptr)
  {
    return buff+get_offset(get_size_of_rec_offset(), ref_ptr);
  }

  void store_next_rec_ref(uchar *ref_ptr, uchar *ref)
  {
    store_offset(get_size_of_rec_offset(), ref_ptr, (ulong) (ref-buff));
  } 

  /*
    Get the position of the embedded key value for the current
    record pointed to by get_curr_rec().
  */ 
  uchar *get_curr_emb_key()
  {
    return get_curr_rec()+data_fields_offset;
  }

  /*
    Get the position of the embedded key value pointed to by a reference
    stored at ref_ptr. The stored reference is actually the offset from
    the beginning of the join buffer.
  */  
  uchar *get_emb_key(uchar *ref_ptr)
  {
    return buff+get_offset(get_size_of_rec_offset(), ref_ptr);
  }

  /* 
    Store the reference to an embedded key at the position key_ref_ptr.
    The position of the embedded key is pointed to by ref. The stored
    reference is actually the offset from the beginning of the join buffer.
  */  
  void store_emb_key_ref(uchar *ref_ptr, uchar *ref)
  {
    store_offset(get_size_of_rec_offset(), ref_ptr, (ulong) (ref-buff));
  }
  
  /* Get the total length of all prefixes of a record in hashed join buffer */ 
  uint get_prefix_length() 
  { 
    return base_prefix_length + get_size_of_rec_offset();
  }

  /* 
    Get maximum size of the additional space per record used for
    the hash table with record keys
  */
  uint get_max_key_addon_space_per_record();

  /* 
    Calculate how much space in the buffer would not be occupied by
    records, key entries and additional memory for the MMR buffer.
  */ 
  ulong rem_space() 
  { 
    return max(last_key_entry-end_pos-aux_buff_size,0);
  }

  /* Skip record from a hashed join buffer if its match flag is on */
  bool skip_recurrent_match();

  /* Search for a key in the hash table of the join buffer */
  bool key_search(uchar *key, uint key_len, uchar **key_ref_ptr);

  /* Reallocate the join buffer of a hashed join cache */
  int realloc_buffer();

public:

  /* Initialize a hashed join cache */       
  int init();

  /* Reset the buffer of a hashed join cache for reading/writing */
  void reset(bool for_writing);

  /* Add a record into the buffer of a hashed join cache */
  bool put_record();

  /* Read the next record from the buffer of a hashed join cache */
  bool get_record();

  /*
    Shall check whether all records in a key chain have 
    their match flags set on
  */   
  virtual bool check_all_match_flags_for_key(uchar *key_chain_ptr);

  uint get_next_key(uchar **key); 
  
  /* Get the head of the record chain attached to the current key entry */ 
  uchar *get_curr_key_chain()
  {
    return get_next_rec_ref(curr_key_entry+key_entry_length-
                            get_size_of_rec_offset());
  }
  
};


/*
  The class JOIN_TAB_SCAN is a companion class for the classes JOIN_CACHE_BNL
  and JOIN_CACHE_BNLH. Actually the class implements the iterator over the
  table joinded by BNL/BNLH join algorithm.
  The virtual functions open, next and close are called for any iteration over
  the table. The function open is called to initiate the process of the 
  iteration. The function next shall read the next record from the joined
  table. The record is read into the record buffer of the joined table.
  The record is to be matched with records from the join cache buffer. 
  The function close shall perform the finalizing actions for the iteration.
*/
   
class JOIN_TAB_SCAN: public Sql_alloc
{

private:
  /* TRUE if this is the first record from the joined table to iterate over */
  bool is_first_record;

protected:

  /* The joined table to be iterated over */
  JOIN_TAB *join_tab;
  /* The join cache used to join the table join_tab */ 
  JOIN_CACHE *cache;
  /* 
    Representation of the executed multi-way join through which
    all needed context can be accessed.  
  */   
  JOIN *join;

public:
  
  JOIN_TAB_SCAN(JOIN *j, JOIN_TAB *tab)
  {
    join= j;
    join_tab= tab;
    cache= join_tab->cache;
  }

  virtual ~JOIN_TAB_SCAN() {}
 
  /* 
    Shall calculate the increment of the auxiliary buffer for a record
    write if such a buffer is used by the table scan object 
  */
  virtual uint aux_buffer_incr(ulong recno) { return 0; }

  /* Initiate the process of iteration over the joined table */
  virtual int open();
  /* 
    Shall read the next candidate for matches with records from 
    the join buffer.
  */
  virtual int next();
  /* 
    Perform the finalizing actions for the process of iteration
    over the joined_table.
  */ 
  virtual void close();

};

/*
  The class JOIN_CACHE_BNL is used when the BNL join algorithm is
  employed to perform a join operation   
*/

class JOIN_CACHE_BNL :public JOIN_CACHE
{
private:
  /* 
    The number of the records in the join buffer that have to be
    checked yet for a match with the current record of join_tab 
    read into the record buffer.
  */
  uint rem_records;

protected:

  bool prepare_look_for_matches(bool skip_last);

  uchar *get_next_candidate_for_match();

  bool skip_recurrent_candidate_for_match(uchar *rec_ptr);

  void read_next_candidate_for_match(uchar *rec_ptr);

public:

  /* 
    This constructor creates an unlinked BNL join cache. The cache is to be
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter.
  */   
  JOIN_CACHE_BNL(JOIN *j, JOIN_TAB *tab)
  { 
    join= j;
    join_tab= tab;
    prev_cache= next_cache= 0;
  }

  /* 
    This constructor creates a linked BNL join cache. The cache is to be 
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter. The parameter 'prev' specifies the previous
    cache object to which this cache is linked.
  */   
  JOIN_CACHE_BNL(JOIN *j, JOIN_TAB *tab, JOIN_CACHE *prev)
  { 
    join= j;
    join_tab= tab;
    prev_cache= prev;
    next_cache= 0;
    if (prev)
      prev->next_cache= this;
  }

  /* Initialize the BNL cache */       
  int init();

  bool is_key_access() { return FALSE; }

};


/*
  The class JOIN_CACHE_BNLH is used when the BNLH join algorithm is
  employed to perform a join operation   
*/

class JOIN_CACHE_BNLH :public JOIN_CACHE_HASHED
{

protected:

  /* 
    The pointer to the last record from the circular list of the records
    that  match the join key built out of the record in the join buffer for
    the join_tab table
  */
  uchar *last_matching_rec_ref_ptr;
  /*
    The pointer to the next current  record from the circular list of the
    records that match the join key built out of the record in the join buffer
    for the join_tab table. This pointer is used by the class method 
    get_next_candidate_for_match to iterate over records from the circular
    list.
  */
  uchar *next_matching_rec_ref_ptr;

  /*
    Get the chain of records from buffer matching the current candidate
    record for join
  */
  uchar *get_matching_chain_by_join_key();

  bool prepare_look_for_matches(bool skip_last);

  uchar *get_next_candidate_for_match();

  bool skip_recurrent_candidate_for_match(uchar *rec_ptr);

  void read_next_candidate_for_match(uchar *rec_ptr);

public:

  /* 
    This constructor creates an unlinked BNLH join cache. The cache is to be
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter.
  */   
  JOIN_CACHE_BNLH(JOIN *j, JOIN_TAB *tab)
  { 
    join= j;
    join_tab= tab;
    prev_cache= next_cache= 0;
  }

  /* 
    This constructor creates a linked BNLH join cache. The cache is to be 
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter. The parameter 'prev' specifies the previous
    cache object to which this cache is linked.
  */   
  JOIN_CACHE_BNLH(JOIN *j, JOIN_TAB *tab, JOIN_CACHE *prev)
  { 
    join= j;
    join_tab= tab;
    prev_cache= prev;
    next_cache= 0;
    if (prev)
      prev->next_cache= this;
  }

  /* Initialize the BNLH cache */       
  int init();

  bool is_key_access() { return TRUE; }

};


/*
  The class JOIN_TAB_SCAN_MRR is a companion class for the classes
  JOIN_CACHE_BKA and JOIN_CACHE_BKAH. Actually the class implements the
  iterator over the records from join_tab selected by BKA/BKAH join
  algorithm as the candidates to be joined. 
  The virtual functions open, next and close are called for any iteration over
  join_tab record candidates. The function open is called to initiate the
  process of the iteration. The function next shall read the next record from
  the set of the record candidates. The record is read into the record buffer
  of the joined table. The function close shall perform the finalizing actions
  for the iteration.
*/
   
class JOIN_TAB_SCAN_MRR: public JOIN_TAB_SCAN
{
  /* Interface object to generate key ranges for MRR */
  RANGE_SEQ_IF range_seq_funcs;

  /* Number of ranges to be processed by the MRR interface */
  uint ranges;

  /* Flag to to be passed to the MRR interface */ 
  uint mrr_mode;

  /* MRR buffer assotiated with this join cache */
  HANDLER_BUFFER mrr_buff;

  /* Shall initialize the MRR buffer */
  virtual void init_mrr_buff()
  {
    cache->setup_aux_buffer(mrr_buff);
  }

public:

  JOIN_TAB_SCAN_MRR(JOIN *j, JOIN_TAB *tab, uint flags, RANGE_SEQ_IF rs_funcs)
    :JOIN_TAB_SCAN(j, tab), range_seq_funcs(rs_funcs), mrr_mode(flags) {}

  uint aux_buffer_incr(ulong recno);

  int open();
 
  int next();

};

/*
  The class JOIN_CACHE_BKA is used when the BKA join algorithm is
  employed to perform a join operation   
*/

class JOIN_CACHE_BKA :public JOIN_CACHE
{
private:

  /* Flag to to be passed to the companion JOIN_TAB_SCAN_MRR object */
  uint mrr_mode;

  /* 
    This value is set to 1 by the class prepare_look_for_matches method
    and back to 0 by the class get_next_candidate_for_match method
  */
  uint rem_records;

  /*
    This field contains the current association label set by a call of
    the multi_range_read_next handler function.
    See the function JOIN_CACHE_BKA::get_curr_key_association()
  */
  uchar *curr_association;

protected:

  /* 
    Get the number of ranges in the cache buffer passed to the MRR
    interface. For each record its own range is passed.
  */
  uint get_number_of_ranges_for_mrr() { return records; }

 /*
   Setup the MRR buffer as the space between the last record put
   into the join buffer and the very end of the join buffer 
 */
  int setup_aux_buffer(HANDLER_BUFFER &aux_buff)
  {
    aux_buff.buffer= end_pos;
    aux_buff.buffer_end= buff+buff_size;
    return 0;
  }

  bool prepare_look_for_matches(bool skip_last);

  uchar *get_next_candidate_for_match();

  bool skip_recurrent_candidate_for_match(uchar *rec_ptr);

  void read_next_candidate_for_match(uchar *rec_ptr);

public:

  /* 
    This constructor creates an unlinked BKA join cache. The cache is to be
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter.
    The MRR mode initially is set to 'flags'.
  */   
  JOIN_CACHE_BKA(JOIN *j, JOIN_TAB *tab, uint flags)
  { 
    join= j;
    join_tab= tab;
    prev_cache= next_cache= 0;
    mrr_mode= flags;
  }

  /* 
    This constructor creates a linked BKA join cache. The cache is to be 
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter. The parameter 'prev' specifies the previous
    cache object to which this cache is linked.
    The MRR mode initially is set to 'flags'.
  */   
  JOIN_CACHE_BKA(JOIN *j, JOIN_TAB *tab, uint flags, JOIN_CACHE *prev)
  { 
    join= j;
    join_tab= tab;
    prev_cache= prev;
    next_cache= 0;
    if (prev)
      prev->next_cache= this;
    mrr_mode= flags;
  }
  
  uchar **get_curr_association_ptr() { return &curr_association; }

  /* Initialize the BKA cache */       
  int init();

  bool is_key_access() { return TRUE; }

  /* Get the key built over the next record from the join buffer */
  uint get_next_key(uchar **key);

  /* Check index condition of the joined table for a record from BKA cache */
  bool skip_index_tuple(char *range_info);

};



/*
  The class JOIN_CACHE_BKAH is used when the BKAH join algorithm is
  employed to perform a join operation   
*/

class JOIN_CACHE_BKAH :public JOIN_CACHE_BNLH
{

private:
  /* Flag to to be passed to the companion JOIN_TAB_SCAN_MRR object */
  uint mrr_mode;

  /* 
    This flag is set to TRUE if the implementation of the MRR interface cannot
    handle range association labels and does not return them to the caller of
    the multi_range_read_next handler function. E.g. the implementation of
    the MRR inteface for the Falcon engine could not return association
    labels to the caller of multi_range_read_next.
    The flag is set by JOIN_CACHE_BKA::init() and is not ever changed.
  */       
  bool no_association;

  /* 
    This field contains the association label returned by the 
    multi_range_read_next function.
    See the function JOIN_CACHE_BKAH::get_curr_key_association()
  */
  uchar *curr_matching_chain;

protected:

  uint get_number_of_ranges_for_mrr() { return key_entries; }

  /* 
    Initialize the MRR buffer allocating some space within the join buffer.
    The entire space between the last record put into the join buffer and the
    last key entry added to the hash table is used for the MRR buffer.
  */
  int setup_aux_buffer(HANDLER_BUFFER &aux_buff)
  {
    aux_buff.buffer= end_pos;
    aux_buff.buffer_end= last_key_entry;
    return 0;
  }

  bool prepare_look_for_matches(bool skip_last);

  /*
    The implementations of the methods
    - get_next_candidate_for_match
    - skip_recurrent_candidate_for_match
    - read_next_candidate_for_match
    are inherited from the JOIN_CACHE_BNLH class
  */

public:

  /* 
    This constructor creates an unlinked BKAH join cache. The cache is to be
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter.
    The MRR mode initially is set to 'flags'.
  */   
  JOIN_CACHE_BKAH(JOIN *j, JOIN_TAB *tab, uint flags) :JOIN_CACHE_BNLH(j, tab)
  { 
    mrr_mode= flags;
  }

  /* 
    This constructor creates a linked BKAH join cache. The cache is to be 
    used to join table 'tab' to the result of joining the previous tables 
    specified by the 'j' parameter. The parameter 'prev' specifies the previous
    cache object to which this cache is linked.
    The MRR mode initially is set to 'flags'.
  */   
  JOIN_CACHE_BKAH(JOIN *j, JOIN_TAB *tab, uint flags, JOIN_CACHE *prev)
    :JOIN_CACHE_BNLH(j, tab, prev)
  { 
    mrr_mode= flags;
  }

  uchar **get_curr_association_ptr() { return &curr_matching_chain; }

  /* Initialize the BKAH cache */       
  int init();

  /* Check index condition of the joined table for a record from BKAH cache */
  bool skip_index_tuple(char *range_info);
};


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;
} 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;
  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; 
  
  /**
    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
  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;
  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;
    group_optimized_away= 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;
  }

  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 && tmp_table_param.sum_func_count != 0 &&
	    !group_list && 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);

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 transform_and_change_in_all_fields(Item** item,
                                          Item_transformer transformer);
};


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);
void copy_funcs(Item **func_ptr);
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 };
  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 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);
    }
  }
  const char *name() const { return field_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);
    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)
  {}
  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;
    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)
  {
  }
  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 *reopt_rec_count, double *reopt_cost,
                                double *sj_inner_fanout);
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, bool other_tbls_ok,
                     bool factor_out);

/****************************************************************************
  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 */