item.cc

/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult 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; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


#ifdef __GNUC__
#pragma implementation				// gcc: Class implementation
#endif

#include "mysql_priv.h"
#include <m_ctype.h>
#include "my_dir.h"

static void mark_as_dependent(THD *thd,
			      SELECT_LEX *last, SELECT_LEX *current,
			      Item_ident *item);

const String my_null_string("NULL", 4, default_charset_info);

/*****************************************************************************
** Item functions
*****************************************************************************/

/* Init all special items */

void item_init(void)
{
  item_user_lock_init();
}

Item::Item():
  fixed(0)
{
  marker= 0;
  maybe_null=null_value=with_sum_func=unsigned_flag=0;
  collation.set(default_charset(), DERIVATION_COERCIBLE);
  name= 0;
  decimals= 0; max_length= 0;

  /* Put item in free list so that we can free all items at end */
  THD *thd= current_thd;
  next= thd->free_list;
  thd->free_list= this;
  /*
    Item constructor can be called during execution other then SQL_COM
    command => we should check thd->lex->current_select on zero (thd->lex
    can be uninitialised)
  */
  if (thd->lex->current_select)
  {
    enum_parsing_place place= 
      thd->lex->current_select->parsing_place;
    if (place == SELECT_LIST ||
	place == IN_HAVING)
      thd->lex->current_select->select_n_having_items++;
  }
}

/*
  Constructor used by Item_field, Item_ref & agregate (sum) functions.
  Used for duplicating lists in processing queries with temporary
  tables
*/
Item::Item(THD *thd, Item *item):
  str_value(item->str_value),
  name(item->name),
  max_length(item->max_length),
  marker(item->marker),
  decimals(item->decimals),
  maybe_null(item->maybe_null),
  null_value(item->null_value),
  unsigned_flag(item->unsigned_flag),
  with_sum_func(item->with_sum_func),
  fixed(item->fixed),
  collation(item->collation)
{
  next= thd->free_list;				// Put in free list
  thd->free_list= this;
}


void Item::print_item_w_name(String *str)
{
  print(str);
  if (name)
  {
    str->append(" AS `", 5);
    str->append(name);
    str->append('`');
  }
}


Item_ident::Item_ident(const char *db_name_par,const char *table_name_par,
		       const char *field_name_par)
  :orig_db_name(db_name_par), orig_table_name(table_name_par), 
   orig_field_name(field_name_par),
   db_name(db_name_par), table_name(table_name_par), 
   field_name(field_name_par), cached_field_index(NO_CACHED_FIELD_INDEX), 
   cached_table(0), depended_from(0)
{
  name = (char*) field_name_par;
}

// Constructor used by Item_field & Item_ref (see Item comment)
Item_ident::Item_ident(THD *thd, Item_ident *item)
  :Item(thd, item),
   orig_db_name(item->orig_db_name),
   orig_table_name(item->orig_table_name), 
   orig_field_name(item->orig_field_name),
   db_name(item->db_name),
   table_name(item->table_name),
   field_name(item->field_name),
   cached_field_index(item->cached_field_index),
   cached_table(item->cached_table),
   depended_from(item->depended_from)
{}

void Item_ident::cleanup()
{
  DBUG_ENTER("Item_ident::cleanup");
  DBUG_PRINT("enter", ("b:%s(%s), t:%s(%s), f:%s(%s)",
		       db_name, orig_db_name,
		       table_name, orig_table_name,
		       field_name, orig_field_name));
  Item::cleanup();
  db_name= orig_db_name; 
  table_name= orig_table_name;
  field_name= orig_field_name;
  DBUG_VOID_RETURN;
}

bool Item_ident::remove_dependence_processor(byte * arg)
{
  DBUG_ENTER("Item_ident::remove_dependence_processor");
  if (depended_from == (st_select_lex *) arg)
    depended_from= 0;
  DBUG_RETURN(0);
}


bool Item::check_cols(uint c)
{
  if (c != 1)
  {
    my_error(ER_OPERAND_COLUMNS, MYF(0), c);
    return 1;
  }
  return 0;
}


void Item::set_name(const char *str, uint length, CHARSET_INFO *cs)
{
  if (!length)
  {
    /* Empty string, used by AS or internal function like last_insert_id() */
    name= (char*) str;
    return;
  }
  if (cs->ctype)
  {
    // This will probably need a better implementation in the future:
    // a function in CHARSET_INFO structure.
    while (length && !my_isgraph(cs,*str))
    {						// Fix problem with yacc
      length--;
      str++;
    }
  }
  if (!my_charset_same(cs, system_charset_info))
  {
    uint32 res_length;
    name= sql_strmake_with_convert(str, length, cs,
				   MAX_ALIAS_NAME, system_charset_info,
				   &res_length);
  }
  else
    name=sql_strmake(str, min(length,MAX_ALIAS_NAME));
}


/*
  This function is called when:
  - Comparing items in the WHERE clause (when doing where optimization)
  - When trying to find an ORDER BY/GROUP BY item in the SELECT part
*/

bool Item::eq(const Item *item, bool binary_cmp) const
{
  return type() == item->type() && name && item->name &&
    !my_strcasecmp(system_charset_info,name,item->name);
}


Item *Item::safe_charset_converter(CHARSET_INFO *tocs)
{
  /*
    Don't allow automatic conversion to non-Unicode charsets,
    as it potentially loses data.
  */
  if (!(tocs->state & MY_CS_UNICODE))
    return NULL; // safe conversion is not possible
  return new Item_func_conv_charset(this, tocs);
}


Item *Item_string::safe_charset_converter(CHARSET_INFO *tocs)
{
  Item_string *conv;
  uint conv_errors;
  String tmp, cstr, *ostr= val_str(&tmp);
  cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(), tocs, &conv_errors);
  if (conv_errors || !(conv= new Item_string(cstr.ptr(), cstr.length(),
                                             cstr.charset(),
                                             collation.derivation)))
  {
    /*
      Safe conversion is not possible (or EOM).
      We could not convert a string into the requested character set
      without data loss. The target charset does not cover all the
      characters from the string. Operation cannot be done correctly.
    */
    return NULL;
  }
  conv->str_value.copy();
  return conv;
}


bool Item_string::eq(const Item *item, bool binary_cmp) const
{
  if (type() == item->type())
  {
    if (binary_cmp)
      return !stringcmp(&str_value, &item->str_value);
    return !sortcmp(&str_value, &item->str_value, collation.collation);
  }
  return 0;
}


/*
  Get the value of the function as a TIME structure.
  As a extra convenience the time structure is reset on error!
 */

bool Item::get_date(TIME *ltime,uint fuzzydate)
{
  char buff[40];
  String tmp(buff,sizeof(buff), &my_charset_bin),*res;
  if (!(res=val_str(&tmp)) ||
      str_to_datetime_with_warn(res->ptr(), res->length(),
                                ltime, fuzzydate) <= MYSQL_TIMESTAMP_ERROR)
  {
    bzero((char*) ltime,sizeof(*ltime));
    return 1;
  }
  return 0;
}

/*
  Get time of first argument.
  As a extra convenience the time structure is reset on error!
 */

bool Item::get_time(TIME *ltime)
{
  char buff[40];
  String tmp(buff,sizeof(buff),&my_charset_bin),*res;
  if (!(res=val_str(&tmp)) ||
      str_to_time_with_warn(res->ptr(), res->length(), ltime))
  {
    bzero((char*) ltime,sizeof(*ltime));
    return 1;
  }
  return 0;
}

CHARSET_INFO *Item::default_charset()
{
  return current_thd->variables.collation_connection;
}


/*
   Aggregate two collations together taking
   into account their coercibility (aka derivation):

   0 == DERIVATION_EXPLICIT  - an explicitely written COLLATE clause
   1 == DERIVATION_NONE      - a mix of two different collations
   2 == DERIVATION_IMPLICIT  - a column
   3 == DERIVATION_COERCIBLE - a string constant

   The most important rules are:

   1. If collations are the same:
      chose this collation, and the strongest derivation.

   2. If collations are different:
     - Character sets may differ, but only if conversion without
       data loss is possible. The caller provides flags whether
       character set conversion attempts should be done. If no
       flags are substituted, then the character sets must be the same.
       Currently processed flags are:
         MY_COLL_ALLOW_SUPERSET_CONV  - allow conversion to a superset
         MY_COLL_ALLOW_COERCIBLE_CONV - allow conversion of a coercible value
     - two EXPLICIT collations produce an error, e.g. this is wrong:
       CONCAT(expr1 collate latin1_swedish_ci, expr2 collate latin1_german_ci)
     - the side with smaller derivation value wins,
       i.e. a column is stronger than a string constant,
       an explicit COLLATE clause is stronger than a column.
     - if derivations are the same, we have DERIVATION_NONE,
       we'll wait for an explicit COLLATE clause which possibly can
       come from another argument later: for example, this is valid,
       but we don't know yet when collecting the first two arguments:
         CONCAT(latin1_swedish_ci_column,
                latin1_german1_ci_column,
                expr COLLATE latin1_german2_ci)
*/
bool DTCollation::aggregate(DTCollation &dt, uint flags)
{
  nagg++;
  if (!my_charset_same(collation, dt.collation))
  {
    /* 
       We do allow to use binary strings (like BLOBS)
       together with character strings.
       Binaries have more precedance than a character
       string of the same derivation.
    */
    if (collation == &my_charset_bin)
    {
      if (derivation <= dt.derivation)
	; // Do nothing
      else
      {
	set(dt); 
        strong= nagg;
      }
    }
    else if (dt.collation == &my_charset_bin)
    {
      if (dt.derivation <= derivation)
      {
        set(dt);
        strong= nagg;
      }
      else
       ; // Do nothing
    }
    else if ((flags & MY_COLL_ALLOW_SUPERSET_CONV) &&
             derivation < dt.derivation &&
             collation->state & MY_CS_UNICODE)
    {
      // Do nothing
    }
    else if ((flags & MY_COLL_ALLOW_SUPERSET_CONV) &&
             dt.derivation < derivation &&
             dt.collation->state & MY_CS_UNICODE)
    {
      set(dt);
      strong= nagg;
    }
    else if ((flags & MY_COLL_ALLOW_COERCIBLE_CONV) &&
             derivation < dt.derivation &&
             dt.derivation >= DERIVATION_COERCIBLE)
    {
      // Do nothing;
    }
    else if ((flags & MY_COLL_ALLOW_COERCIBLE_CONV) &&
             dt.derivation < derivation &&
             derivation >= DERIVATION_COERCIBLE)
    {
      set(dt);
      strong= nagg;
    }
    else
    {
      // Cannot apply conversion
      set(0, DERIVATION_NONE);
      return 1;
    }
  }
  else if (derivation < dt.derivation)
  {
    // Do nothing
  }
  else if (dt.derivation < derivation)
  {
    set(dt);
    strong= nagg;
  }
  else
  { 
    if (collation == dt.collation)
    {
      // Do nothing
    }
    else 
    {
      if (derivation == DERIVATION_EXPLICIT)
      {
	set(0, DERIVATION_NONE);
	return 1;
      }
      CHARSET_INFO *bin= get_charset_by_csname(collation->csname, 
					       MY_CS_BINSORT,MYF(0));
      set(bin, DERIVATION_NONE);
    }
  }
  return 0;
}

Item_field::Item_field(Field *f)
  :Item_ident(NullS, f->table_name, f->field_name)
{
  set_field(f);
  /*
    field_name and talbe_name should not point to garbage
    if this item is to be reused
  */
  orig_table_name= orig_field_name= "";
}

Item_field::Item_field(THD *thd, Field *f)
  :Item_ident(f->table->table_cache_key, f->table_name, f->field_name)
{
  /*
    We always need to provide Item_field with a fully qualified field
    name to avoid ambiguity when executing prepared statements like
    SELECT * from d1.t1, d2.t1; (assuming d1.t1 and d2.t1 have columns
    with same names).
    This is because prepared statements never deal with wildcards in
    select list ('*') and always fix fields using fully specified path
    (i.e. db.table.column).
    No check for OOM: if db_name is NULL, we'll just get
    "Field not found" error.
    We need to copy db_name, table_name and field_name because they must
    be allocated in the statement memory, not in table memory (the table
    structure can go away and pop up again between subsequent executions
    of a prepared statement).
  */
  if (thd->current_arena->is_stmt_prepare())
  {
    if (db_name)
      orig_db_name= thd->strdup(db_name);
    orig_table_name= thd->strdup(table_name);
    orig_field_name= thd->strdup(field_name);
    /*
      We don't restore 'name' in cleanup because it's not changed
      during execution. Still we need it to point to persistent
      memory if this item is to be reused.
    */
    name= (char*) orig_field_name;
  }
  set_field(f);
}

// Constructor need to process subselect with temporary tables (see Item)
Item_field::Item_field(THD *thd, Item_field *item)
  :Item_ident(thd, item),
   field(item->field),
   result_field(item->result_field)
{
  collation.set(DERIVATION_IMPLICIT);
}

void Item_field::set_field(Field *field_par)
{
  field=result_field=field_par;			// for easy coding with fields
  maybe_null=field->maybe_null();
  max_length=field_par->field_length;
  decimals= field->decimals();
  table_name=field_par->table_name;
  field_name=field_par->field_name;
  db_name=field_par->table->table_cache_key;
  unsigned_flag=test(field_par->flags & UNSIGNED_FLAG);
  collation.set(field_par->charset(), DERIVATION_IMPLICIT);
  fixed= 1;
}


/*
  Reset this item to point to a field from the new temporary table.
  This is used when we create a new temporary table for each execution
  of prepared statement.
*/

void Item_field::reset_field(Field *f)
{
  set_field(f);
  /* 'name' is pointing at field->field_name of old field */
  name= (char*) f->field_name;
}

const char *Item_ident::full_name() const
{
  char *tmp;
  if (!table_name || !field_name)
    return field_name ? field_name : name ? name : "tmp_field";
  if (db_name && db_name[0])
  {
    tmp=(char*) sql_alloc((uint) strlen(db_name)+(uint) strlen(table_name)+
			  (uint) strlen(field_name)+3);
    strxmov(tmp,db_name,".",table_name,".",field_name,NullS);
  }
  else
  {
    if (table_name[0])
    {
      tmp= (char*) sql_alloc((uint) strlen(table_name) +
			     (uint) strlen(field_name) + 2);
      strxmov(tmp, table_name, ".", field_name, NullS);
    }
    else
      tmp= (char*) field_name;
  }
  return tmp;
}

/* ARGSUSED */
String *Item_field::val_str(String *str)
{
  DBUG_ASSERT(fixed == 1);
  if ((null_value=field->is_null()))
    return 0;
  str->set_charset(str_value.charset());
  return field->val_str(str,&str_value);
}

double Item_field::val()
{
  DBUG_ASSERT(fixed == 1);
  if ((null_value=field->is_null()))
    return 0.0;
  return field->val_real();
}

longlong Item_field::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if ((null_value=field->is_null()))
    return 0;
  return field->val_int();
}


String *Item_field::str_result(String *str)
{
  if ((null_value=result_field->is_null()))
    return 0;
  str->set_charset(str_value.charset());
  return result_field->val_str(str,&str_value);
}

bool Item_field::get_date(TIME *ltime,uint fuzzydate)
{
  if ((null_value=field->is_null()) || field->get_date(ltime,fuzzydate))
  {
    bzero((char*) ltime,sizeof(*ltime));
    return 1;
  }
  return 0;
}

bool Item_field::get_date_result(TIME *ltime,uint fuzzydate)
{
  if ((null_value=result_field->is_null()) ||
      result_field->get_date(ltime,fuzzydate))
  {
    bzero((char*) ltime,sizeof(*ltime));
    return 1;
  }
  return 0;
}

bool Item_field::get_time(TIME *ltime)
{
  if ((null_value=field->is_null()) || field->get_time(ltime))
  {
    bzero((char*) ltime,sizeof(*ltime));
    return 1;
  }
  return 0;
}

double Item_field::val_result()
{
  if ((null_value=result_field->is_null()))
    return 0.0;
  return result_field->val_real();
}

longlong Item_field::val_int_result()
{
  if ((null_value=result_field->is_null()))
    return 0;
  return result_field->val_int();
}


bool Item_field::eq(const Item *item, bool binary_cmp) const
{
  if (item->type() != FIELD_ITEM)
    return 0;
  
  Item_field *item_field= (Item_field*) item;
  if (item_field->field)
    return item_field->field == field;
  /*
    We may come here when we are trying to find a function in a GROUP BY
    clause from the select list.
    In this case the '100 % correct' way to do this would be to first
    run fix_fields() on the GROUP BY item and then retry this function, but
    I think it's better to relax the checking a bit as we will in
    most cases do the correct thing by just checking the field name.
    (In cases where we would choose wrong we would have to generate a
    ER_NON_UNIQ_ERROR).
  */
  return (!my_strcasecmp(system_charset_info, item_field->name,
			 field_name) &&
	  (!item_field->table_name ||
	   (!my_strcasecmp(table_alias_charset, item_field->table_name,
			   table_name) &&
	    (!item_field->db_name ||
	     (item_field->db_name && !strcmp(item_field->db_name,
					     db_name))))));
}


table_map Item_field::used_tables() const
{
  if (field->table->const_table)
    return 0;					// const item
  return (depended_from ? OUTER_REF_TABLE_BIT : field->table->map);
}


Item *Item_field::get_tmp_table_item(THD *thd)
{
  Item_field *new_item= new Item_field(thd, this);
  if (new_item)
    new_item->field= new_item->result_field;
  return new_item;
}


/*
  Create an item from a string we KNOW points to a valid longlong/ulonglong
  end \0 terminated number string
*/

Item_int::Item_int(const char *str_arg, uint length)
{
  char *end_ptr= (char*) str_arg + length;
  int error;
  value= my_strtoll10(str_arg, &end_ptr, &error);
  max_length= (uint) (end_ptr - str_arg);
  name= (char*) str_arg;
  fixed= 1;
}


String *Item_int::val_str(String *str)
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  str->set(value, &my_charset_bin);
  return str;
}

void Item_int::print(String *str)
{
  // my_charset_bin is good enough for numbers
  str_value.set(value, &my_charset_bin);
  str->append(str_value);
}


Item_uint::Item_uint(const char *str_arg, uint length):
  Item_int(str_arg, length)
{
  unsigned_flag= 1;
}


String *Item_uint::val_str(String *str)
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  str->set((ulonglong) value, &my_charset_bin);
  return str;
}


void Item_uint::print(String *str)
{
  // latin1 is good enough for numbers
  str_value.set((ulonglong) value, default_charset());
  str->append(str_value);
}


String *Item_real::val_str(String *str)
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  str->set(value,decimals,&my_charset_bin);
  return str;
}


void Item_string::print(String *str)
{
  str->append('_');
  str->append(collation.collation->csname);
  str->append('\'');
  str_value.print(str);
  str->append('\'');
}

bool Item_null::eq(const Item *item, bool binary_cmp) const
{ return item->type() == type(); }
double Item_null::val()
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  null_value=1;
  return 0.0;
}
longlong Item_null::val_int()
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  null_value=1;
  return 0;
}
/* ARGSUSED */
String *Item_null::val_str(String *str)
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  null_value=1;
  return 0;
}


Item *Item_null::safe_charset_converter(CHARSET_INFO *tocs)
{
  collation.set(tocs);
  return this;
}

/*********************** Item_param related ******************************/

/* 
  Default function of Item_param::set_param_func, so in case
  of malformed packet the server won't SIGSEGV
*/

static void
default_set_param_func(Item_param *param,
                       uchar **pos __attribute__((unused)),
                       ulong len __attribute__((unused)))
{
  param->set_null();
}

Item_param::Item_param(unsigned pos_in_query_arg) :
  state(NO_VALUE),
  item_result_type(STRING_RESULT),
  /* Don't pretend to be a literal unless value for this item is set. */
  item_type(PARAM_ITEM),
  param_type(MYSQL_TYPE_STRING),
  pos_in_query(pos_in_query_arg),
  set_param_func(default_set_param_func)
{
  name= (char*) "?";
  /* 
    Since we can't say whenever this item can be NULL or cannot be NULL
    before mysql_stmt_execute(), so we assuming that it can be NULL until
    value is set.
  */
  maybe_null= 1;
}

void Item_param::set_null()
{
  DBUG_ENTER("Item_param::set_null");
  /* These are cleared after each execution by reset() method */
  max_length= 0;
  null_value= 1;
  /* 
    Because of NULL and string values we need to set max_length for each new
    placeholder value: user can submit NULL for any placeholder type, and 
    string length can be different in each execution.
  */
  max_length= 0;
  decimals= 0;
  state= NULL_VALUE;
  DBUG_VOID_RETURN;
}

void Item_param::set_int(longlong i, uint32 max_length_arg)
{
  DBUG_ENTER("Item_param::set_int");
  value.integer= (longlong) i;
  state= INT_VALUE;
  max_length= max_length_arg;
  decimals= 0;
  maybe_null= 0;
  DBUG_VOID_RETURN;
}

void Item_param::set_double(double d)
{
  DBUG_ENTER("Item_param::set_double");
  value.real= d;
  state= REAL_VALUE;
  max_length= DBL_DIG + 8;
  decimals= NOT_FIXED_DEC;
  maybe_null= 0;
  DBUG_VOID_RETURN;
}


/*
  Set parameter value from TIME value.

  SYNOPSIS
    set_time()
      tm             - datetime value to set (time_type is ignored)
      type           - type of datetime value
      max_length_arg - max length of datetime value as string

  NOTE
    If we value to be stored is not normalized, zero value will be stored
    instead and proper warning will be produced. This function relies on
    the fact that even wrong value sent over binary protocol fits into
    MAX_DATE_STRING_REP_LENGTH buffer.
*/
void Item_param::set_time(TIME *tm, timestamp_type type, uint32 max_length_arg)
{ 
  DBUG_ENTER("Item_param::set_time");

  value.time= *tm;
  value.time.time_type= type;

  if (value.time.year > 9999 || value.time.month > 12 ||
      value.time.day > 31 ||
      type != MYSQL_TIMESTAMP_TIME && value.time.hour > 23 ||
      value.time.minute > 59 || value.time.second > 59)
  {
    char buff[MAX_DATE_STRING_REP_LENGTH];
    uint length= my_TIME_to_str(&value.time, buff);
    make_truncated_value_warning(current_thd, buff, length, type);
    set_zero_time(&value.time, MYSQL_TIMESTAMP_ERROR);
  }

  state= TIME_VALUE;
  maybe_null= 0;
  max_length= max_length_arg;
  decimals= 0;
  DBUG_VOID_RETURN;
}


bool Item_param::set_str(const char *str, ulong length)
{
  DBUG_ENTER("Item_param::set_str");
  /*
    Assign string with no conversion: data is converted only after it's
    been written to the binary log.
  */
  uint dummy_errors;
  if (str_value.copy(str, length, &my_charset_bin, &my_charset_bin,
                     &dummy_errors))
    DBUG_RETURN(TRUE);
  state= STRING_VALUE;
  maybe_null= 0;
  /* max_length and decimals are set after charset conversion */
  /* sic: str may be not null-terminated, don't add DBUG_PRINT here */
  DBUG_RETURN(FALSE);
}


bool Item_param::set_longdata(const char *str, ulong length)
{
  DBUG_ENTER("Item_param::set_longdata");

  /*
    If client character set is multibyte, end of long data packet
    may hit at the middle of a multibyte character.  Additionally,
    if binary log is open we must write long data value to the
    binary log in character set of client. This is why we can't
    convert long data to connection character set as it comes
    (here), and first have to concatenate all pieces together,
    write query to the binary log and only then perform conversion.
  */
  if (str_value.append(str, length, &my_charset_bin))
    DBUG_RETURN(TRUE);
  state= LONG_DATA_VALUE;
  maybe_null= 0;

  DBUG_RETURN(FALSE);
}


/*
  Set parameter value from user variable value.

  SYNOPSIS
   set_from_user_var
     thd   Current thread
     entry User variable structure (NULL means use NULL value)

  RETURN
    0 OK
    1 Out of memort
*/

bool Item_param::set_from_user_var(THD *thd, const user_var_entry *entry)
{
  DBUG_ENTER("Item_param::set_from_user_var");
  if (entry && entry->value)
  {
    item_result_type= entry->type;
    switch (entry->type) {
    case REAL_RESULT:
      set_double(*(double*)entry->value);
      item_type= Item::REAL_ITEM;
      item_result_type= REAL_RESULT;
      break;
    case INT_RESULT:
      set_int(*(longlong*)entry->value, 21);
      item_type= Item::INT_ITEM;
      item_result_type= INT_RESULT;
      break;
    case STRING_RESULT:
    {
      CHARSET_INFO *fromcs= entry->collation.collation;
      CHARSET_INFO *tocs= thd->variables.collation_connection;
      uint32 dummy_offset;

      value.cs_info.character_set_client= fromcs;
      /*
        Setup source and destination character sets so that they
        are different only if conversion is necessary: this will
        make later checks easier.
      */
      value.cs_info.final_character_set_of_str_value=
        String::needs_conversion(0, fromcs, tocs, &dummy_offset) ?
        tocs : fromcs;
      /*
        Exact value of max_length is not known unless data is converted to
        charset of connection, so we have to set it later.
      */
      item_type= Item::STRING_ITEM;
      item_result_type= STRING_RESULT;

      if (set_str((const char *)entry->value, entry->length))
        DBUG_RETURN(1);
      break;
    }
    default:
      DBUG_ASSERT(0);
      set_null();
    }
  }
  else
    set_null();

  DBUG_RETURN(0);
}

/*
    Resets parameter after execution.
  
  SYNOPSIS
     Item_param::reset()
 
  NOTES
    We clear null_value here instead of setting it in set_* methods, 
    because we want more easily handle case for long data.
*/

void Item_param::reset()
{
  /* Shrink string buffer if it's bigger than max possible CHAR column */
  if (str_value.alloced_length() > MAX_CHAR_WIDTH)
    str_value.free();
  else
    str_value.length(0);
  str_value_ptr.length(0);
  /*
    We must prevent all charset conversions untill data has been written
    to the binary log.
  */
  str_value.set_charset(&my_charset_bin);
  state= NO_VALUE;
  maybe_null= 1;
  null_value= 0;
  /*
    Don't reset item_type to PARAM_ITEM: it's only needed to guard
    us from item optimizations at prepare stage, when item doesn't yet
    contain a literal of some kind.
    In all other cases when this object is accessed its value is
    set (this assumption is guarded by 'state' and
    DBUG_ASSERTS(state != NO_VALUE) in all Item_param::get_*
    methods).
  */
}


int Item_param::save_in_field(Field *field, bool no_conversions)
{
  field->set_notnull();

  switch (state) {
  case INT_VALUE:
    return field->store(value.integer);
  case REAL_VALUE:
    return field->store(value.real);
  case TIME_VALUE:
    field->store_time(&value.time, value.time.time_type);
    return 0;
  case STRING_VALUE:
  case LONG_DATA_VALUE:
    return field->store(str_value.ptr(), str_value.length(),
                        str_value.charset());
  case NULL_VALUE:
    return set_field_to_null_with_conversions(field, no_conversions);
  case NO_VALUE:
  default:
    DBUG_ASSERT(0);
  }
  return 1;
}


bool Item_param::get_time(TIME *res)
{
  if (state == TIME_VALUE)
  {
    *res= value.time;
    return 0;
  }
  /*
    If parameter value isn't supplied assertion will fire in val_str()
    which is called from Item::get_time().
  */
  return Item::get_time(res);
}


bool Item_param::get_date(TIME *res, uint fuzzydate)
{
  if (state == TIME_VALUE)
  {
    *res= value.time;
    return 0;
  }
  return Item::get_date(res, fuzzydate);
}


double Item_param::val() 
{
  switch (state) {
  case REAL_VALUE:
    return value.real;
  case INT_VALUE:
    return (double) value.integer;
  case STRING_VALUE:
  case LONG_DATA_VALUE:
    {
      int dummy_err;
      return my_strntod(str_value.charset(), (char*) str_value.ptr(),
                        str_value.length(), (char**) 0, &dummy_err);
    }
  case TIME_VALUE:
    /*
      This works for example when user says SELECT ?+0.0 and supplies
      time value for the placeholder.
    */
    return ulonglong2double(TIME_to_ulonglong(&value.time));
  case NULL_VALUE:
    return 0.0;
  default:
    DBUG_ASSERT(0);
  }
  return 0.0;
} 


longlong Item_param::val_int() 
{ 
  switch (state) {
  case REAL_VALUE:
    return (longlong) (value.real + (value.real > 0 ? 0.5 : -0.5));
  case INT_VALUE:
    return value.integer;
  case STRING_VALUE:
  case LONG_DATA_VALUE:
    {
      int dummy_err;
      return my_strntoll(str_value.charset(), str_value.ptr(),
                         str_value.length(), 10, (char**) 0, &dummy_err);
    }
  case TIME_VALUE:
    return (longlong) TIME_to_ulonglong(&value.time);
  case NULL_VALUE:
    return 0; 
  default:
    DBUG_ASSERT(0);
  }
  return 0;
}


String *Item_param::val_str(String* str) 
{ 
  switch (state) {
  case STRING_VALUE:
  case LONG_DATA_VALUE:
    return &str_value_ptr;
  case REAL_VALUE:
    str->set(value.real, NOT_FIXED_DEC, &my_charset_bin);
    return str;
  case INT_VALUE:
    str->set(value.integer, &my_charset_bin);
    return str;
  case TIME_VALUE:
  {
    if (str->reserve(MAX_DATE_STRING_REP_LENGTH))
      break;
    str->length((uint) my_TIME_to_str(&value.time, (char*) str->ptr()));
    str->set_charset(&my_charset_bin);
    return str;
  }
  case NULL_VALUE:
    return NULL; 
  default:
    DBUG_ASSERT(0);
  }
  return str;
}

/*
  Return Param item values in string format, for generating the dynamic 
  query used in update/binary logs
  TODO: change interface and implementation to fill log data in place
  and avoid one more memcpy/alloc between str and log string.
*/

const String *Item_param::query_val_str(String* str) const
{
  switch (state) {
  case INT_VALUE:
    str->set(value.integer, &my_charset_bin);
    break;
  case REAL_VALUE:
    str->set(value.real, NOT_FIXED_DEC, &my_charset_bin);
    break;
  case TIME_VALUE:
    {
      char *buf, *ptr;
      str->length(0);
      /*
        TODO: in case of error we need to notify replication
        that binary log contains wrong statement 
      */
      if (str->reserve(MAX_DATE_STRING_REP_LENGTH+3))
        break; 

      /* Create date string inplace */
      buf= str->c_ptr_quick();
      ptr= buf;
      *ptr++= '\'';
      ptr+= (uint) my_TIME_to_str(&value.time, ptr);
      *ptr++= '\'';
      str->length((uint32) (ptr - buf));
      break;
    }
  case STRING_VALUE:
  case LONG_DATA_VALUE:
    {
      char *buf, *ptr;
      str->length(0);
      if (str->reserve(str_value.length()*2+3))
        break;

      buf= str->c_ptr_quick();
      ptr= buf;
      *ptr++= '\'';
      ptr+= escape_string_for_mysql(str_value.charset(), ptr,
                                    str_value.ptr(), str_value.length());
      *ptr++= '\'';
      str->length(ptr - buf);
      break;
    }
  case NULL_VALUE:
    return &my_null_string;
  default:
    DBUG_ASSERT(0);
  }
  return str;
}


/*
  Convert string from client character set to the character set of
  connection.
*/

bool Item_param::convert_str_value(THD *thd)
{
  bool rc= FALSE;
  if (state == STRING_VALUE || state == LONG_DATA_VALUE)
  {
    /*
      Check is so simple because all charsets were set up properly
      in setup_one_conversion_function, where typecode of
      placeholder was also taken into account: the variables are different
      here only if conversion is really necessary.
    */
    if (value.cs_info.final_character_set_of_str_value !=
        value.cs_info.character_set_client)
    {
      rc= thd->convert_string(&str_value,
                              value.cs_info.character_set_client,
                              value.cs_info.final_character_set_of_str_value);
    }
    else
      str_value.set_charset(value.cs_info.final_character_set_of_str_value);
    /* Here str_value is guaranteed to be in final_character_set_of_str_value */

    max_length= str_value.length();
    decimals= 0;
    /*
      str_value_ptr is returned from val_str(). It must be not alloced
      to prevent it's modification by val_str() invoker.
    */
    str_value_ptr.set(str_value.ptr(), str_value.length(),
                      str_value.charset());
  }
  return rc;
}

/* End of Item_param related */


void Item_copy_string::copy()
{
  String *res=item->val_str(&str_value);
  if (res && res != &str_value)
    str_value.copy(*res);
  null_value=item->null_value;
}

/* ARGSUSED */
String *Item_copy_string::val_str(String *str)
{
  // Item_copy_string is used without fix_fields call
  if (null_value)
    return (String*) 0;
  return &str_value;
}


int Item_copy_string::save_in_field(Field *field, bool no_conversions)
{
  if (null_value)
    return set_field_to_null(field);
  field->set_notnull();
  return field->store(str_value.ptr(),str_value.length(),
		      collation.collation);
}

/*
  Functions to convert item to field (for send_fields)
*/

/* ARGSUSED */
bool Item::fix_fields(THD *thd,
		      struct st_table_list *list,
		      Item ** ref)
{

  // We do not check fields which are fixed during construction
  DBUG_ASSERT(fixed == 0 || basic_const_item());
  fixed= 1;
  return 0;
}

double Item_ref_null_helper::val()
{
  DBUG_ASSERT(fixed == 1);
  double tmp= (*ref)->val_result();
  owner->was_null|= null_value= (*ref)->null_value;
  return tmp;
}


longlong Item_ref_null_helper::val_int()
{
  DBUG_ASSERT(fixed == 1);
  longlong tmp= (*ref)->val_int_result();
  owner->was_null|= null_value= (*ref)->null_value;
  return tmp;
}


String* Item_ref_null_helper::val_str(String* s)
{
  DBUG_ASSERT(fixed == 1);
  String* tmp= (*ref)->str_result(s);
  owner->was_null|= null_value= (*ref)->null_value;
  return tmp;
}


bool Item_ref_null_helper::get_date(TIME *ltime, uint fuzzydate)
{  
  return (owner->was_null|= null_value= (*ref)->get_date(ltime, fuzzydate));
}


/*
  Mark item and SELECT_LEXs as dependent if it is not outer resolving

  SYNOPSIS
    mark_as_dependent()
    thd - thread handler
    last - select from which current item depend
    current  - current select
    item - item which should be marked
*/

static void mark_as_dependent(THD *thd, SELECT_LEX *last, SELECT_LEX *current,
			      Item_ident *item)
{
  // store pointer on SELECT_LEX from which item is dependent
  item->depended_from= last;
  current->mark_as_dependent(last);
  if (thd->lex->describe & DESCRIBE_EXTENDED)
  {
    char warn_buff[MYSQL_ERRMSG_SIZE];
    sprintf(warn_buff, ER(ER_WARN_FIELD_RESOLVED),
	    (item->db_name?item->db_name:""), (item->db_name?".":""),
	    (item->table_name?item->table_name:""), (item->table_name?".":""),
	    item->field_name,
	    current->select_number, last->select_number);
    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
		 ER_WARN_FIELD_RESOLVED, warn_buff);
  }
}


bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
{
  DBUG_ASSERT(fixed == 0);
  if (!field)					// If field is not checked
  {
    TABLE_LIST *where= 0;
    bool upward_lookup= 0;
    Field *tmp= (Field *)not_found_field;
    if ((tmp= find_field_in_tables(thd, this, tables, &where, 0)) ==
	not_found_field)
    {
      /*
	We can't find table field in table list of current select,
	consequently we have to find it in outer subselect(s).
	We can't join lists of outer & current select, because of scope
	of view rules. For example if both tables (outer & current) have
	field 'field' it is not mistake to refer to this field without
	mention of table name, but if we join tables in one list it will
	cause error ER_NON_UNIQ_ERROR in find_field_in_tables.
      */
      SELECT_LEX *last= 0;
#ifdef EMBEDDED_LIBRARY
      thd->net.last_errno= 0;
#endif
      TABLE_LIST *table_list;
      Item **refer= (Item **)not_found_item;
      uint counter;
      bool not_used;
      // Prevent using outer fields in subselects, that is not supported now
      SELECT_LEX *cursel= (SELECT_LEX *) thd->lex->current_select;
      if (cursel->master_unit()->first_select()->linkage != DERIVED_TABLE_TYPE)
      {
	SELECT_LEX_UNIT *prev_unit= cursel->master_unit();
	for (SELECT_LEX *sl= prev_unit->outer_select();
	     sl;
	     sl= (prev_unit= sl->master_unit())->outer_select())
	{
	  upward_lookup= 1;
	  table_list= (last= sl)->get_table_list();
	  if (sl->resolve_mode == SELECT_LEX::INSERT_MODE && table_list)
	  {
            /*
              it is primary INSERT st_select_lex => skip first table
              resolving
            */
	    table_list= table_list->next;
	  }

	  Item_subselect *prev_subselect_item= prev_unit->item;
          enum_parsing_place place=
            prev_subselect_item->parsing_place;
          /*
            check table fields only if subquery used somewhere out of HAVING
            or outer SELECT do not use groupping (i.e. tables are
            accessable)
          */
          if ((place != IN_HAVING ||
               (sl->with_sum_func == 0 && sl->group_list.elements == 0)) &&
              (tmp= find_field_in_tables(thd, this,
                                         table_list, &where,
                                         0)) != not_found_field)
          {
            if (!tmp)
              return -1;
            prev_subselect_item->used_tables_cache|= tmp->table->map;
            prev_subselect_item->const_item_cache= 0;
            break;
          }
	  if (sl->resolve_mode == SELECT_LEX::SELECT_MODE &&
	      (refer= find_item_in_list(this, sl->item_list, &counter,
                                        REPORT_EXCEPT_NOT_FOUND,
                                        &not_used)) !=
	       (Item **) not_found_item)
	  {
	    if (*refer && (*refer)->fixed) // Avoid crash in case of error
	    {
	      prev_subselect_item->used_tables_cache|= (*refer)->used_tables();
	      prev_subselect_item->const_item_cache&= (*refer)->const_item();
	    }
	    break;
	  }

	  // Reference is not found => depend from outer (or just error)
	  prev_subselect_item->used_tables_cache|= OUTER_REF_TABLE_BIT;
	  prev_subselect_item->const_item_cache= 0;

	  if (sl->master_unit()->first_select()->linkage ==
	      DERIVED_TABLE_TYPE)
	    break; // do not look over derived table
	}
      }
      if (!tmp)
	return -1;
      else if (!refer)
	return 1;
      else if (tmp == not_found_field && refer == (Item **)not_found_item)
      {
	if (upward_lookup)
	{
	  // We can't say exactly what absend table or field
	  my_printf_error(ER_BAD_FIELD_ERROR, ER(ER_BAD_FIELD_ERROR), MYF(0),
			  full_name(), thd->where);
	}
	else
	{
	  // Call to report error
	  find_field_in_tables(thd, this, tables, &where, 1);
	}
	return -1;
      }
      else if (refer != (Item **)not_found_item)
      {
	if (!(*refer)->fixed)
	{
	  my_error(ER_ILLEGAL_REFERENCE, MYF(0), name,
		   "forward reference in item list");
	  return -1;
	}
	Item_ref *rf= new Item_ref(last->ref_pointer_array + counter,
                                   (char *)table_name, (char *)field_name,
                                   this);
	if (!rf)
	  return 1;
        thd->change_item_tree(ref, rf);
	/*
	  rf is Item_ref => never substitute other items (in this case)
	  during fix_fields() => we can use rf after fix_fields()
	*/
	if (rf->fix_fields(thd, tables, ref) || rf->check_cols(1))
	  return 1;

	mark_as_dependent(thd, last, cursel, rf);
	return 0;
      }
      else
      {
	mark_as_dependent(thd, last, cursel, this);
	if (last->having_fix_field)
	{
	  Item_ref *rf;
          rf= new Item_ref((where->db[0] ? where->db : 0),
                           (char*) where->alias, (char*) field_name);
	  if (!rf)
	    return 1;
          thd->change_item_tree(ref, rf);
	  /*
	    rf is Item_ref => never substitute other items (in this case)
	    during fix_fields() => we can use rf after fix_fields()
	  */
	  return rf->fix_fields(thd, tables, ref) ||  rf->check_cols(1);
	}
      }
    }
    else if (!tmp)
      return -1;

    set_field(tmp);
  }
  else if (thd->set_query_id && field->query_id != thd->query_id)
  {
    /* We only come here in unions */
    TABLE *table=field->table;
    field->query_id=thd->query_id;
    table->used_fields++;
    table->used_keys.intersect(field->part_of_key);
    fixed= 1;
  }
  return 0;
}

void Item_field::cleanup()
{
  DBUG_ENTER("Item_field::cleanup");
  Item_ident::cleanup();
  /*
    Even if this object was created by direct link to field in setup_wild()
    it will be linked correctly next tyme by name of field and table alias.
    I.e. we can drop 'field'.
   */
  field= result_field= 0;
  DBUG_VOID_RETURN;
}

void Item::init_make_field(Send_field *tmp_field,
			   enum enum_field_types field_type)
{
  char *empty_name= (char*) "";
  tmp_field->db_name=		empty_name;
  tmp_field->org_table_name=	empty_name;
  tmp_field->org_col_name=	empty_name;
  tmp_field->table_name=	empty_name;
  tmp_field->col_name=		name;
  tmp_field->charsetnr=         collation.collation->number;
  tmp_field->flags=             (maybe_null ? 0 : NOT_NULL_FLAG) | 
                                (my_binary_compare(collation.collation) ?
                                 BINARY_FLAG : 0);
  tmp_field->type=field_type;
  tmp_field->length=max_length;
  tmp_field->decimals=decimals;
  if (unsigned_flag)
    tmp_field->flags |= UNSIGNED_FLAG;
}

void Item::make_field(Send_field *tmp_field)
{
  init_make_field(tmp_field, field_type());
}


void Item_empty_string::make_field(Send_field *tmp_field)
{
  init_make_field(tmp_field,FIELD_TYPE_VAR_STRING);
}


enum_field_types Item::field_type() const
{
  return ((result_type() == STRING_RESULT) ? FIELD_TYPE_VAR_STRING :
	  (result_type() == INT_RESULT) ? FIELD_TYPE_LONGLONG :
	  FIELD_TYPE_DOUBLE);
}


Field *Item::tmp_table_field_from_field_type(TABLE *table)
{
  /*
    The field functions defines a field to be not null if null_ptr is not 0
  */
  uchar *null_ptr= maybe_null ? (uchar*) "" : 0;

  switch (field_type()) {
  case MYSQL_TYPE_DECIMAL:
    return new Field_decimal((char*) 0, max_length, null_ptr, 0, Field::NONE,
			     name, table, decimals, 0, unsigned_flag);
  case MYSQL_TYPE_TINY:
    return new Field_tiny((char*) 0, max_length, null_ptr, 0, Field::NONE,
			  name, table, 0, unsigned_flag);
  case MYSQL_TYPE_SHORT:
    return new Field_short((char*) 0, max_length, null_ptr, 0, Field::NONE,
			   name, table, 0, unsigned_flag);
  case MYSQL_TYPE_LONG:
    return new Field_long((char*) 0, max_length, null_ptr, 0, Field::NONE,
			  name, table, 0, unsigned_flag);
#ifdef HAVE_LONG_LONG
  case MYSQL_TYPE_LONGLONG:
    return new Field_longlong((char*) 0, max_length, null_ptr, 0, Field::NONE,
			      name, table, 0, unsigned_flag);
#endif
  case MYSQL_TYPE_FLOAT:
    return new Field_float((char*) 0, max_length, null_ptr, 0, Field::NONE,
			   name, table, decimals, 0, unsigned_flag);
  case MYSQL_TYPE_DOUBLE:
    return new Field_double((char*) 0, max_length, null_ptr, 0, Field::NONE,
			    name, table, decimals, 0, unsigned_flag);
  case MYSQL_TYPE_NULL:
    return new Field_null((char*) 0, max_length, Field::NONE,
			  name, table, &my_charset_bin);
  case MYSQL_TYPE_NEWDATE:
  case MYSQL_TYPE_INT24:
    return new Field_medium((char*) 0, max_length, null_ptr, 0, Field::NONE,
			    name, table, 0, unsigned_flag);
  case MYSQL_TYPE_DATE:
    return new Field_date(maybe_null, name, table, &my_charset_bin);
  case MYSQL_TYPE_TIME:
    return new Field_time(maybe_null, name, table, &my_charset_bin);
  case MYSQL_TYPE_TIMESTAMP:
  case MYSQL_TYPE_DATETIME:
    return new Field_datetime(maybe_null, name, table, &my_charset_bin);
  case MYSQL_TYPE_YEAR:
    return new Field_year((char*) 0, max_length, null_ptr, 0, Field::NONE,
			  name, table);
  default:
    /* This case should never be choosen */
    DBUG_ASSERT(0);
    /* If something goes awfully wrong, it's better to get a string than die */
  case MYSQL_TYPE_ENUM:
  case MYSQL_TYPE_SET:
  case MYSQL_TYPE_VAR_STRING:
    if (max_length > 255)
      break;					// If blob
    return new Field_varstring(max_length, maybe_null, name, table,
			       collation.collation);
  case MYSQL_TYPE_STRING:
    if (max_length > 255)			// If blob
      break;
    return new Field_string(max_length, maybe_null, name, table,
			    collation.collation);
  case MYSQL_TYPE_TINY_BLOB:
  case MYSQL_TYPE_MEDIUM_BLOB:
  case MYSQL_TYPE_LONG_BLOB:
  case MYSQL_TYPE_BLOB:
  case MYSQL_TYPE_GEOMETRY:
    break;					// Blob handled outside of case
  }

  /* blob is special as it's generated for both blobs and long strings */
  return new Field_blob(max_length, maybe_null, name, table,
			collation.collation);
}


/* ARGSUSED */
void Item_field::make_field(Send_field *tmp_field)
{
  field->make_field(tmp_field);
  DBUG_ASSERT(tmp_field->table_name);
  if (name)
    tmp_field->col_name=name;			// Use user supplied name
}


/*
  Set a field:s value from a item
*/

void Item_field::save_org_in_field(Field *to)
{
  if (field->is_null())
  {
    null_value=1;
    set_field_to_null_with_conversions(to, 1);
  }
  else
  {
    to->set_notnull();
    field_conv(to,field);
    null_value=0;
  }
}

int Item_field::save_in_field(Field *to, bool no_conversions)
{
  if (result_field->is_null())
  {
    null_value=1;
    return set_field_to_null_with_conversions(to, no_conversions);
  }
  else
  {
    to->set_notnull();
    field_conv(to,result_field);
    null_value=0;
  }
  return 0;
}


/*
  Store null in field

  SYNOPSIS
    save_in_field()
    field		Field where we want to store NULL

  DESCRIPTION
    This is used on INSERT.
    Allow NULL to be inserted in timestamp and auto_increment values

  RETURN VALUES
    0	 ok
    1	 Field doesn't support NULL values and can't handle 'field = NULL'
*/   

int Item_null::save_in_field(Field *field, bool no_conversions)
{
  return set_field_to_null_with_conversions(field, no_conversions);
}


/*
  Store null in field

  SYNOPSIS
    save_safe_in_field()
    field		Field where we want to store NULL

  RETURN VALUES
    0	 ok
    1	 Field doesn't support NULL values
*/   

int Item_null::save_safe_in_field(Field *field)
{
  return set_field_to_null(field);
}


int Item::save_in_field(Field *field, bool no_conversions)
{
  int error;
  if (result_type() == STRING_RESULT ||
      result_type() == REAL_RESULT &&
      field->result_type() == STRING_RESULT)
  {
    String *result;
    CHARSET_INFO *cs= collation.collation;
    char buff[MAX_FIELD_WIDTH];		// Alloc buffer for small columns
    str_value.set_quick(buff, sizeof(buff), cs);
    result=val_str(&str_value);
    if (null_value)
    {
      str_value.set_quick(0, 0, cs);
      return set_field_to_null_with_conversions(field, no_conversions);
    }
    field->set_notnull();
    error=field->store(result->ptr(),result->length(),cs);
    str_value.set_quick(0, 0, cs);
  }
  else if (result_type() == REAL_RESULT)
  {
    double nr=val();
    if (null_value)
      return set_field_to_null(field);
    field->set_notnull();
    error=field->store(nr);
  }
  else
  {
    longlong nr=val_int();
    if (null_value)
      return set_field_to_null_with_conversions(field, no_conversions);
    field->set_notnull();
    error=field->store(nr);
  }
  return error;
}


int Item_string::save_in_field(Field *field, bool no_conversions)
{
  String *result;
  result=val_str(&str_value);
  if (null_value)
    return set_field_to_null(field);
  field->set_notnull();
  return field->store(result->ptr(),result->length(),collation.collation);
}

int Item_uint::save_in_field(Field *field, bool no_conversions)
{
  /*
    TODO: To be fixed when wen have a
    field->store(longlong, unsigned_flag) method 
  */
  return Item_int::save_in_field(field, no_conversions);
}


int Item_int::save_in_field(Field *field, bool no_conversions)
{
  longlong nr=val_int();
  if (null_value)
    return set_field_to_null(field);
  field->set_notnull();
  return field->store(nr);
}

Item_num *Item_uint::neg()
{
  return new Item_real(name, - ((double) value), 0, max_length);
}

int Item_real::save_in_field(Field *field, bool no_conversions)
{
  double nr=val();
  if (null_value)
    return set_field_to_null(field);
  field->set_notnull();
  return field->store(nr);
}

/****************************************************************************
** varbinary item
** In string context this is a binary string
** In number context this is a longlong value.
****************************************************************************/

inline uint char_val(char X)
{
  return (uint) (X >= '0' && X <= '9' ? X-'0' :
		 X >= 'A' && X <= 'Z' ? X-'A'+10 :
		 X-'a'+10);
}


Item_varbinary::Item_varbinary(const char *str, uint str_length)
{
  name=(char*) str-2;				// Lex makes this start with 0x
  max_length=(str_length+1)/2;
  char *ptr=(char*) sql_alloc(max_length+1);
  if (!ptr)
    return;
  str_value.set(ptr,max_length,&my_charset_bin);
  char *end=ptr+max_length;
  if (max_length*2 != str_length)
    *ptr++=char_val(*str++);			// Not even, assume 0 prefix
  while (ptr != end)
  {
    *ptr++= (char) (char_val(str[0])*16+char_val(str[1]));
    str+=2;
  }
  *ptr=0;					// Keep purify happy
  collation.set(&my_charset_bin, DERIVATION_COERCIBLE);
  fixed= 1;
}

longlong Item_varbinary::val_int()
{
  // following assert is redundant, because fixed=1 assigned in constructor
  DBUG_ASSERT(fixed == 1);
  char *end=(char*) str_value.ptr()+str_value.length(),
       *ptr=end-min(str_value.length(),sizeof(longlong));

  ulonglong value=0;
  for (; ptr != end ; ptr++)
    value=(value << 8)+ (ulonglong) (uchar) *ptr;
  return (longlong) value;
}


int Item_varbinary::save_in_field(Field *field, bool no_conversions)
{
  int error;
  field->set_notnull();
  if (field->result_type() == STRING_RESULT)
  {
    error=field->store(str_value.ptr(),str_value.length(),collation.collation);
  }
  else
  {
    longlong nr=val_int();
    error=field->store(nr);
  }
  return error;
}


/*
  Pack data in buffer for sending
*/

bool Item_null::send(Protocol *protocol, String *packet)
{
  return protocol->store_null();
}

/*
  This is only called from items that is not of type item_field
*/

bool Item::send(Protocol *protocol, String *buffer)
{
  bool result;
  enum_field_types type;
  LINT_INIT(result);

  switch ((type=field_type())) {
  default:
  case MYSQL_TYPE_NULL:
  case MYSQL_TYPE_DECIMAL:
  case MYSQL_TYPE_ENUM:
  case MYSQL_TYPE_SET:
  case MYSQL_TYPE_TINY_BLOB:
  case MYSQL_TYPE_MEDIUM_BLOB:
  case MYSQL_TYPE_LONG_BLOB:
  case MYSQL_TYPE_BLOB:
  case MYSQL_TYPE_GEOMETRY:
  case MYSQL_TYPE_STRING:
  case MYSQL_TYPE_VAR_STRING:
  {
    String *res;
    if ((res=val_str(buffer)))
      result= protocol->store(res->ptr(),res->length(),res->charset());
    break;
  }
  case MYSQL_TYPE_TINY:
  {
    longlong nr;
    nr= val_int();
    if (!null_value)
      result= protocol->store_tiny(nr);
    break;
  }
  case MYSQL_TYPE_SHORT:
  {
    longlong nr;
    nr= val_int();
    if (!null_value)
      result= protocol->store_short(nr);
    break;
  }
  case MYSQL_TYPE_INT24:
  case MYSQL_TYPE_LONG:
  {
    longlong nr;
    nr= val_int();
    if (!null_value)
      result= protocol->store_long(nr);
    break;
  }
  case MYSQL_TYPE_LONGLONG:
  {
    longlong nr;
    nr= val_int();
    if (!null_value)
      result= protocol->store_longlong(nr, unsigned_flag);
    break;
  }
  case MYSQL_TYPE_FLOAT:
  {
    float nr;
    nr= (float) val();
    if (!null_value)
      result= protocol->store(nr, decimals, buffer);
    break;
  }
  case MYSQL_TYPE_DOUBLE:
  {
    double nr;
    nr= val();
    if (!null_value)
      result= protocol->store(nr, decimals, buffer);
    break;
  }
  case MYSQL_TYPE_DATETIME:
  case MYSQL_TYPE_DATE:
  case MYSQL_TYPE_TIMESTAMP:
  {
    TIME tm;
    get_date(&tm, TIME_FUZZY_DATE);
    if (!null_value)
    {
      if (type == MYSQL_TYPE_DATE)
	return protocol->store_date(&tm);
      else
	result= protocol->store(&tm);
    }
    break;
  }
  case MYSQL_TYPE_TIME:
  {
    TIME tm;
    get_time(&tm);
    if (!null_value)
      result= protocol->store_time(&tm);
    break;
  }
  }
  if (null_value)
    result= protocol->store_null();
  return result;
}


bool Item_field::send(Protocol *protocol, String *buffer)
{
  return protocol->store(result_field);
}


/*
  This is used for HAVING clause
  Find field in select list having the same name
*/

bool Item_ref::fix_fields(THD *thd,TABLE_LIST *tables, Item **reference)
{
  DBUG_ASSERT(fixed == 0);
  uint counter;
  bool not_used;
  if (!ref)
  {
    TABLE_LIST *where= 0, *table_list;
    bool upward_lookup= 0;
    SELECT_LEX_UNIT *prev_unit= thd->lex->current_select->master_unit();
    SELECT_LEX *sl= prev_unit->outer_select();
    /*
      Finding only in current select will be performed for selects that have 
      not outer one and for derived tables (which not support using outer 
      fields for now)
    */
    if ((ref= find_item_in_list(this, 
				*(thd->lex->current_select->get_item_list()),
				&counter,
				((sl && 
				  thd->lex->current_select->master_unit()->
				  first_select()->linkage !=
				  DERIVED_TABLE_TYPE) ? 
				  REPORT_EXCEPT_NOT_FOUND :
				  REPORT_ALL_ERRORS ), &not_used)) ==
	(Item **)not_found_item)
    {
      Field *tmp= (Field*) not_found_field;
      SELECT_LEX *last= 0;
      upward_lookup= 1;
      /*
	We can't find table field in select list of current select,
	consequently we have to find it in outer subselect(s).
	We can't join lists of outer & current select, because of scope
	of view rules. For example if both tables (outer & current) have
	field 'field' it is not mistake to refer to this field without
	mention of table name, but if we join tables in one list it will
	cause error ER_NON_UNIQ_ERROR in find_item_in_list.
      */
      for ( ; sl ; sl= (prev_unit= sl->master_unit())->outer_select())
      {
	last= sl;
	Item_subselect *prev_subselect_item= prev_unit->item;
	if (sl->resolve_mode == SELECT_LEX::SELECT_MODE &&
	    (ref= find_item_in_list(this, sl->item_list,
                                    &counter, REPORT_EXCEPT_NOT_FOUND,
                                    &not_used)) !=
	   (Item **)not_found_item)
	{
	  if (*ref && (*ref)->fixed) // Avoid crash in case of error
	  {
	    prev_subselect_item->used_tables_cache|= (*ref)->used_tables();
	    prev_subselect_item->const_item_cache&= (*ref)->const_item();
	  }
	  break;
	}
	table_list= sl->get_table_list();
	if (sl->resolve_mode == SELECT_LEX::INSERT_MODE && table_list)
	{
	  // it is primary INSERT st_select_lex => skip first table resolving
	  table_list= table_list->next;
	}
        enum_parsing_place place=
            prev_subselect_item->parsing_place;
        /*
          check table fields only if subquery used somewhere out of HAVING
          or SELECT list or outer SELECT do not use groupping (i.e. tables
          are accessable)
        */
        if ((place != IN_HAVING ||
             (sl->with_sum_func == 0 && sl->group_list.elements == 0)) &&
            (tmp= find_field_in_tables(thd, this,
                                       table_list, &where,
                                       0)) != not_found_field)
        {
          prev_subselect_item->used_tables_cache|= tmp->table->map;
          prev_subselect_item->const_item_cache= 0;
          break;
        }
        // Reference is not found => depend from outer (or just error)
	prev_subselect_item->used_tables_cache|= OUTER_REF_TABLE_BIT;
	prev_subselect_item->const_item_cache= 0;

	if (sl->master_unit()->first_select()->linkage ==
	    DERIVED_TABLE_TYPE)
	  break; // do not look over derived table
      }

      if (!ref)
	return 1;
      if (!tmp)
	return -1;
      if (ref == (Item **)not_found_item && tmp == not_found_field)
      {
	if (upward_lookup)
	{
	  // We can't say exactly what absend (table or field)
	  my_printf_error(ER_BAD_FIELD_ERROR, ER(ER_BAD_FIELD_ERROR), MYF(0),
			  full_name(), thd->where);
	}
	else
	{
	  // Call to report error
	  find_item_in_list(this,
			    *(thd->lex->current_select->get_item_list()),
			    &counter, REPORT_ALL_ERRORS, &not_used);
	}
        ref= 0;                                 // Safety
	return 1;
      }
      if (tmp != not_found_field)
      {
        Item_field* fld;
        /*
          Set ref to 0 as we are replacing this item with the found item
          and this will ensure we get an error if this item would be
          used elsewhere
        */
	ref= 0;                                 // Safety
	if (!(fld= new Item_field(tmp)))
	  return 1;
	thd->change_item_tree(reference, fld);
	mark_as_dependent(thd, last, thd->lex->current_select, fld);
	return 0;
      }
      if (!(*ref)->fixed)
      {
        my_error(ER_ILLEGAL_REFERENCE, MYF(0), name,
                 "forward reference in item list");
        return -1;
      }
      mark_as_dependent(thd, last, thd->lex->current_select,
                        this);
      ref= last->ref_pointer_array + counter;
    }
    else if (!ref)
      return 1;
    else
    {
      if (!(*ref)->fixed)
      {
	my_error(ER_ILLEGAL_REFERENCE, MYF(0), name,
		 "forward reference in item list");
	return -1;
      }
      ref= thd->lex->current_select->ref_pointer_array + counter;
    }
  }

  /*
    The following conditional is changed as to correctly identify 
    incorrect references in group functions or forward references 
    with sub-select's / derived tables, while it prevents this 
    check when Item_ref is created in an expression involving 
    summing function, which is to be placed in the user variable.
  */
  if (((*ref)->with_sum_func && name &&
       (depended_from ||
	!(thd->lex->current_select->linkage != GLOBAL_OPTIONS_TYPE &&
	  thd->lex->current_select->having_fix_field))) ||
      !(*ref)->fixed)
  {
    my_error(ER_ILLEGAL_REFERENCE, MYF(0), name, 
	     ((*ref)->with_sum_func?
	      "reference on group function":
	      "forward reference in item list"));
    return 1;
  }
  max_length= (*ref)->max_length;
  maybe_null= (*ref)->maybe_null;
  decimals=   (*ref)->decimals;
  collation.set((*ref)->collation);
  with_sum_func= (*ref)->with_sum_func;
  fixed= 1;

  if (ref && (*ref)->check_cols(1))
    return 1;
  return 0;
}


void Item_ref::print(String *str)
{
  if (ref && *ref)
    (*ref)->print(str);
  else
    Item_ident::print(str);
}


void Item_ref_null_helper::print(String *str)
{
  str->append("<ref_null_helper>(", 18);
  if (ref && *ref)
    (*ref)->print(str);
  else
    str->append('?');
  str->append(')');
}


void Item_null_helper::print(String *str)
{
  str->append("<null_helper>(", 14);
  store->print(str);
  str->append(')');
}


bool Item_default_value::eq(const Item *item, bool binary_cmp) const
{
  return item->type() == DEFAULT_VALUE_ITEM && 
    ((Item_default_value *)item)->arg->eq(arg, binary_cmp);
}


bool Item_default_value::fix_fields(THD *thd,
				    struct st_table_list *table_list,
				    Item **items)
{
  DBUG_ASSERT(fixed == 0);
  if (!arg)
  {
    fixed= 1;
    return 0;
  }
  if (arg->fix_fields(thd, table_list, &arg))
    return 1;
  
  if (arg->type() == REF_ITEM)
  {
    Item_ref *ref= (Item_ref *)arg;
    if (ref->ref[0]->type() != FIELD_ITEM)
    {
      return 1;
    }
    arg= ref->ref[0];
  }
  Item_field *field_arg= (Item_field *)arg;
  Field *def_field= (Field*) sql_alloc(field_arg->field->size_of());
  if (!def_field)
    return 1;
  memcpy(def_field, field_arg->field, field_arg->field->size_of());
  def_field->move_field(def_field->table->default_values -
                        def_field->table->record[0]);
  set_field(def_field);
  return 0;
}

void Item_default_value::print(String *str)
{
  if (!arg)
  {
    str->append("default", 7);
    return;
  }
  str->append("default(", 8);
  arg->print(str);
  str->append(')');
}

bool Item_insert_value::eq(const Item *item, bool binary_cmp) const
{
  return item->type() == INSERT_VALUE_ITEM &&
    ((Item_default_value *)item)->arg->eq(arg, binary_cmp);
}


bool Item_insert_value::fix_fields(THD *thd,
				   struct st_table_list *table_list,
				   Item **items)
{
  DBUG_ASSERT(fixed == 0);
  if (arg->fix_fields(thd, table_list, &arg))
    return 1;

  if (arg->type() == REF_ITEM)
  {
    Item_ref *ref= (Item_ref *)arg;
    if (ref->ref[0]->type() != FIELD_ITEM)
    {
      return 1;
    }
    arg= ref->ref[0];
  }
  Item_field *field_arg= (Item_field *)arg;
  if (field_arg->field->table->insert_values)
  {
    Field *def_field= (Field*) sql_alloc(field_arg->field->size_of());
    if (!def_field)
      return 1;
    memcpy(def_field, field_arg->field, field_arg->field->size_of());
    def_field->move_field(def_field->table->insert_values -
                          def_field->table->record[0]);
    set_field(def_field);
  }
  else
  {
    Field *tmp_field= field_arg->field;
    /* charset doesn't matter here, it's to avoid sigsegv only */
    set_field(new Field_null(0, 0, Field::NONE, tmp_field->field_name,
			     tmp_field->table, &my_charset_bin));
  }
  return 0;
}

void Item_insert_value::print(String *str)
{
  str->append("values(", 7);
  arg->print(str);
  str->append(')');
}

/*
  If item is a const function, calculate it and return a const item
  The original item is freed if not returned
*/

Item_result item_cmp_type(Item_result a,Item_result b)
{
  if (a == STRING_RESULT && b == STRING_RESULT)
    return STRING_RESULT;
  if (a == INT_RESULT && b == INT_RESULT)
    return INT_RESULT;
  else if (a == ROW_RESULT || b == ROW_RESULT)
    return ROW_RESULT;
  return REAL_RESULT;
}


void resolve_const_item(THD *thd, Item **ref, Item *comp_item)
{
  Item *item= *ref;
  Item *new_item;
  if (item->basic_const_item())
    return;                                     // Can't be better
  Item_result res_type=item_cmp_type(comp_item->result_type(),
				     item->result_type());
  char *name=item->name;			// Alloced by sql_alloc

  if (res_type == STRING_RESULT)
  {
    char buff[MAX_FIELD_WIDTH];
    String tmp(buff,sizeof(buff),&my_charset_bin),*result;
    result=item->val_str(&tmp);
    if (item->null_value)
      new_item= new Item_null(name);
    else
    {
      uint length= result->length();
      char *tmp_str= sql_strmake(result->ptr(), length);
      new_item= new Item_string(name, tmp_str, length, result->charset());
    }
  }
  else if (res_type == INT_RESULT)
  {
    longlong result=item->val_int();
    uint length=item->max_length;
    bool null_value=item->null_value;
    new_item= (null_value ? (Item*) new Item_null(name) :
               (Item*) new Item_int(name, result, length));
  }
  else
  {						// It must REAL_RESULT
    double result=item->val();
    uint length=item->max_length,decimals=item->decimals;
    bool null_value=item->null_value;
    new_item= (null_value ? (Item*) new Item_null(name) : (Item*)
               new Item_real(name, result, decimals, length));
  }
  if (new_item)
    thd->change_item_tree(ref, new_item);
}

/*
  Return true if the value stored in the field is equal to the const item
  We need to use this on the range optimizer because in some cases
  we can't store the value in the field without some precision/character loss.
*/

bool field_is_equal_to_item(Field *field,Item *item)
{

  Item_result res_type=item_cmp_type(field->result_type(),
				     item->result_type());
  if (res_type == STRING_RESULT)
  {
    char item_buff[MAX_FIELD_WIDTH];
    char field_buff[MAX_FIELD_WIDTH];
    String item_tmp(item_buff,sizeof(item_buff),&my_charset_bin),*item_result;
    String field_tmp(field_buff,sizeof(field_buff),&my_charset_bin);
    item_result=item->val_str(&item_tmp);
    if (item->null_value)
      return 1;					// This must be true
    field->val_str(&field_tmp);
    return !stringcmp(&field_tmp,item_result);
  }
  if (res_type == INT_RESULT)
    return 1;					// Both where of type int
  double result=item->val();
  if (item->null_value)
    return 1;
  return result == field->val_real();
}

Item_cache* Item_cache::get_cache(Item_result type)
{
  switch (type)
  {
  case INT_RESULT:
    return new Item_cache_int();
  case REAL_RESULT:
    return new Item_cache_real();
  case STRING_RESULT:
    return new Item_cache_str();
  case ROW_RESULT:
    return new Item_cache_row();
  default:
    // should never be in real life
    DBUG_ASSERT(0);
    return 0;
  }
}


void Item_cache::print(String *str)
{
  str->append("<cache>(", 8);
  if (example)
    example->print(str);
  else
    Item::print(str);
  str->append(')');
}


void Item_cache_int::store(Item *item)
{
  value= item->val_int_result();
  null_value= item->null_value;
}


void Item_cache_real::store(Item *item)
{
  value= item->val_result();
  null_value= item->null_value;
}


void Item_cache_str::store(Item *item)
{
  value_buff.set(buffer, sizeof(buffer), item->collation.collation);
  value= item->str_result(&value_buff);
  if ((null_value= item->null_value))
    value= 0;
  else if (value != &value_buff)
  {
    /*
      We copy string value to avoid changing value if 'item' is table field
      in queries like following (where t1.c is varchar):
      select a, 
             (select a,b,c from t1 where t1.a=t2.a) = ROW(a,2,'a'),
             (select c from t1 where a=t2.a)
        from t2;
    */
    value_buff.copy(*value);
    value= &value_buff;
  }
}


double Item_cache_str::val()
{
  DBUG_ASSERT(fixed == 1);
  int err;
  if (value)
    return my_strntod(value->charset(), (char*) value->ptr(),
		      value->length(), (char**) 0, &err);
  else
    return (double)0;
}


longlong Item_cache_str::val_int()
{
  DBUG_ASSERT(fixed == 1);
  int err;
  if (value)
    return my_strntoll(value->charset(), value->ptr(),
		       value->length(), 10, (char**) 0, &err);
  else
    return (longlong)0;
}


bool Item_cache_row::allocate(uint num)
{
  item_count= num;
  THD *thd= current_thd;
  return (!(values= 
	    (Item_cache **) thd->calloc(sizeof(Item_cache *)*item_count)));
}


bool Item_cache_row::setup(Item * item)
{
  example= item;
  if (!values && allocate(item->cols()))
    return 1;
  for (uint i= 0; i < item_count; i++)
  {
    Item *el= item->el(i);
    Item_cache *tmp;
    if (!(tmp= values[i]= Item_cache::get_cache(el->result_type())))
      return 1;
    tmp->setup(el);
  }
  return 0;
}


void Item_cache_row::store(Item * item)
{
  null_value= 0;
  item->bring_value();
  for (uint i= 0; i < item_count; i++)
  {
    values[i]->store(item->el(i));
    null_value|= values[i]->null_value;
  }
}


void Item_cache_row::illegal_method_call(const char *method)
{
  DBUG_ENTER("Item_cache_row::illegal_method_call");
  DBUG_PRINT("error", ("!!! %s method was called for row item", method));
  DBUG_ASSERT(0);
  my_error(ER_OPERAND_COLUMNS, MYF(0), 1);
  DBUG_VOID_RETURN;
}


bool Item_cache_row::check_cols(uint c)
{
  if (c != item_count)
  {
    my_error(ER_OPERAND_COLUMNS, MYF(0), c);
    return 1;
  }
  return 0;
}


bool Item_cache_row::null_inside()
{
  for (uint i= 0; i < item_count; i++)
  {
    if (values[i]->cols() > 1)
    {
      if (values[i]->null_inside())
	return 1;
    }
    else
    {
      values[i]->val_int();
      if (values[i]->null_value)
	return 1;
    }
  }
  return 0;
}


void Item_cache_row::bring_value()
{
  for (uint i= 0; i < item_count; i++)
    values[i]->bring_value();
  return;
}


Item_type_holder::Item_type_holder(THD *thd, Item *item)
  :Item(thd, item), item_type(item->result_type()),
   orig_type(item_type)
{
  DBUG_ASSERT(item->fixed);

  /*
    It is safe assign pointer on field, because it will be used just after
    all JOIN::prepare calls and before any SELECT execution
  */
  if (item->type() == Item::FIELD_ITEM)
    field_example= ((Item_field*) item)->field;
  else
    field_example= 0;
  max_length= real_length(item);
  maybe_null= item->maybe_null;
  collation.set(item->collation);
}


/*
  STRING_RESULT, REAL_RESULT, INT_RESULT, ROW_RESULT

  ROW_RESULT should never appear in Item_type_holder::join_types,
  but it is included in following table just to make table full
  (there DBUG_ASSERT in function to catch ROW_RESULT)
*/
static Item_result type_convertor[4][4]=
{{STRING_RESULT, STRING_RESULT, STRING_RESULT, ROW_RESULT},
 {STRING_RESULT, REAL_RESULT,   REAL_RESULT,   ROW_RESULT},
 {STRING_RESULT, REAL_RESULT,   INT_RESULT,    ROW_RESULT},
 {ROW_RESULT,    ROW_RESULT,    ROW_RESULT,    ROW_RESULT}};


/*
  Values of 'from' field can be stored in 'to' field.

  SYNOPSIS
    is_attr_compatible()
    from        Item which values should be saved
    to          Item where values should be saved

  RETURN
    1   can be saved
    0   can not be saved
*/

inline bool is_attr_compatible(Item *from, Item *to)
{
  return ((to->max_length >= from->max_length) &&
          (to->maybe_null || !from->maybe_null) &&
          (to->result_type() != STRING_RESULT ||
           from->result_type() != STRING_RESULT ||
           my_charset_same(from->collation.collation,
                           to->collation.collation)));
}


bool Item_type_holder::join_types(THD *thd, Item *item)
{
  uint32 new_length= real_length(item);
  bool use_new_field= 0, use_expression_type= 0;
  Item_result new_result_type= type_convertor[item_type][item->result_type()];
  bool item_is_a_field= item->type() == Item::FIELD_ITEM;

  /*
    Check if both items point to fields: in this case we
    can adjust column types of result table in the union smartly.
  */
  if (field_example && item_is_a_field)
  {
    Field *field= ((Item_field *)item)->field;
    /* Can 'field_example' field store data of the column? */
    if ((use_new_field=
         (!field->field_cast_compatible(field_example->field_cast_type()) ||
          !is_attr_compatible(item, this))))
    {
      /*
        The old field can't store value of the new field.
        Check if the new field can store value of the old one.
      */
      use_expression_type|=
        (!field_example->field_cast_compatible(field->field_cast_type()) ||
         !is_attr_compatible(this, item));
    }
  }
  else if (field_example || item_is_a_field)
  {
    /*
      Expression types can't be mixed with field types, we have to use
      expression types.
    */
    use_new_field= 1;                           // make next if test easier
    use_expression_type= 1;
  }

  /* Check whether size/type of the result item should be changed */
  if (use_new_field ||
      (new_result_type != item_type) || (new_length > max_length) ||
      (!maybe_null && item->maybe_null) ||
      (item_type == STRING_RESULT && 
       collation.collation != item->collation.collation))
  {
    const char *old_cs,*old_derivation;
    if (use_expression_type || !item_is_a_field)
      field_example= 0;
    else
    {
      /*
        It is safe to assign a pointer to field here, because it will be used
        before any table is closed.
      */
      field_example= ((Item_field*) item)->field;
    }

    old_cs= collation.collation->name;
    old_derivation= collation.derivation_name();
    if (item_type == STRING_RESULT && collation.aggregate(item->collation))
    {
      my_error(ER_CANT_AGGREGATE_2COLLATIONS, MYF(0),
	       old_cs, old_derivation,
	       item->collation.collation->name,
	       item->collation.derivation_name(),
	       "UNION");
      return 1;
    }

    max_length= max(max_length, new_length);
    decimals= max(decimals, item->decimals);
    maybe_null|= item->maybe_null;
    item_type= new_result_type;
  }
  DBUG_ASSERT(item_type != ROW_RESULT);
  return 0;
}


uint32 Item_type_holder::real_length(Item *item)
{
  if (item->type() == Item::FIELD_ITEM)
    return ((Item_field *)item)->max_disp_length();

  switch (item->result_type())
  {
  case STRING_RESULT:
    return item->max_length;
  case REAL_RESULT:
    return 53;
  case INT_RESULT:
    return 20;
  case ROW_RESULT:
  default:
    DBUG_ASSERT(0); // we should never go there
    return 0;
  }
}

double Item_type_holder::val()
{
  DBUG_ASSERT(0); // should never be called
  return 0.0;
}


longlong Item_type_holder::val_int()
{
  DBUG_ASSERT(0); // should never be called
  return 0;
}


String *Item_type_holder::val_str(String*)
{
  DBUG_ASSERT(0); // should never be called
  return 0;
}

void Item_result_field::cleanup()
{
  DBUG_ENTER("Item_result_field::cleanup()");
  Item::cleanup();
  result_field= 0;
  DBUG_VOID_RETURN;
}

/*****************************************************************************
** Instantiate templates
*****************************************************************************/

#ifdef __GNUC__
template class List<Item>;
template class List_iterator<Item>;
template class List_iterator_fast<Item>;
template class List<List_item>;
#endif