item_sum.cc

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/* Copyright (c) 2000, 2013  Oracle and/or its affiliates. All
   rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

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

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */


#include "sql_priv.h"
#include "sql_select.h"
#include "sql_tmp_table.h"                 // create_tmp_table
#include "sql_resolver.h"                  // setup_order, fix_inner_refs
#include "sql_optimizer.h"                 // JOIN

using std::min;
using std::max;

ulonglong Item_sum::ram_limitation(THD *thd)
{
  return min(thd->variables.tmp_table_size,
      thd->variables.max_heap_table_size);
}


bool Item_sum::init_sum_func_check(THD *thd)
{
  if (!thd->lex->allow_sum_func)
  {
    my_message(ER_INVALID_GROUP_FUNC_USE, ER(ER_INVALID_GROUP_FUNC_USE),
               MYF(0));
    return TRUE;
  }
  /* Set a reference to the nesting set function if there is  any */
  in_sum_func= thd->lex->in_sum_func;
  /* Save a pointer to object to be used in items for nested set functions */
  thd->lex->in_sum_func= this;
  nest_level= thd->lex->current_select->nest_level;
  ref_by= 0;
  aggr_level= -1;
  aggr_sel= NULL;
  max_arg_level= -1;
  max_sum_func_level= -1;
  outer_fields.empty();
  return FALSE;
}

bool Item_sum::check_sum_func(THD *thd, Item **ref)
{
  bool invalid= FALSE;
  nesting_map allow_sum_func= thd->lex->allow_sum_func;
  /*  
    The value of max_arg_level is updated if an argument of the set function
    contains a column reference resolved  against a subquery whose level is
    greater than the current value of max_arg_level.
    max_arg_level cannot be greater than nest level.
    nest level is always >= 0  
  */
  if (nest_level == max_arg_level)
  {
    /*
      The function must be aggregated in the current subquery, 
      If it is there under a construct where it is not allowed 
      we report an error. 
    */ 
    invalid= !(allow_sum_func & ((nesting_map)1 << max_arg_level));
  }
  else if (max_arg_level >= 0 ||
           !(allow_sum_func & ((nesting_map)1 << nest_level)))
  {
    /*
      The set function can be aggregated only in outer subqueries.
      Try to find a subquery where it can be aggregated;
      If we fail to find such a subquery report an error.
    */
    if (register_sum_func(thd, ref))
      return TRUE;
    invalid= aggr_level < 0 &&
             !(allow_sum_func & ((nesting_map)1 << nest_level));
    if (!invalid && thd->variables.sql_mode & MODE_ANSI)
      invalid= aggr_level < 0 && max_arg_level < nest_level;
  }
  if (!invalid && aggr_level < 0)
  {
    aggr_level= nest_level;
    aggr_sel= thd->lex->current_select;
  }
  /*
    By this moment we either found a subquery where the set function is
    to be aggregated  and assigned a value that is  >= 0 to aggr_level,
    or set the value of 'invalid' to TRUE to report later an error. 
  */
  /* 
    Additionally we have to check whether possible nested set functions
    are acceptable here: they are not, if the level of aggregation of
    some of them is less than aggr_level.
  */
  if (!invalid) 
    invalid= aggr_level <= max_sum_func_level;
  if (invalid)  
  {
    my_message(ER_INVALID_GROUP_FUNC_USE, ER(ER_INVALID_GROUP_FUNC_USE),
               MYF(0));
    return TRUE;
  }

  if (in_sum_func)
  {
    /*
      If the set function is nested adjust the value of
      max_sum_func_level for the nesting set function.
      We take into account only enclosed set functions that are to be 
      aggregated on the same level or above of the nest level of 
      the enclosing set function.
      But we must always pass up the max_sum_func_level because it is
      the maximum nested level of all directly and indirectly enclosed
      set functions. We must do that even for set functions that are
      aggregated inside of their enclosing set function's nest level
      because the enclosing function may contain another enclosing
      function that is to be aggregated outside or on the same level
      as its parent's nest level.
    */
    if (in_sum_func->nest_level >= aggr_level)
      set_if_bigger(in_sum_func->max_sum_func_level, aggr_level);
    set_if_bigger(in_sum_func->max_sum_func_level, max_sum_func_level);
  }

  /*
    Check that non-aggregated fields and sum functions aren't mixed in the
    same select in the ONLY_FULL_GROUP_BY mode.
  */
  if (outer_fields.elements)
  {
    Item_field *field;
    /*
      Here we compare the nesting level of the select to which an outer field
      belongs to with the aggregation level of the sum function. All fields in
      the outer_fields list are checked.

      If the nesting level is equal to the aggregation level then the field is
        aggregated by this sum function.
      If the nesting level is less than the aggregation level then the field
        belongs to an outer select. In this case if there is an embedding sum
        function add current field to functions outer_fields list. If there is
        no embedding function then the current field treated as non aggregated
        and the select it belongs to is marked accordingly.
      If the nesting level is greater than the aggregation level then it means
        that this field was added by an inner sum function.
        Consider an example:

          select avg ( <-- we are here, checking outer.f1
            select (
              select sum(outer.f1 + inner.f1) from inner
            ) from outer)
          from most_outer;

        In this case we check that no aggregate functions are used in the
        select the field belongs to. If there are some then an error is
        raised.
    */
    List_iterator<Item_field> of(outer_fields);
    while ((field= of++))
    {
      SELECT_LEX *sel= field->cached_table->select_lex;
      if (sel->nest_level < aggr_level)
      {
        if (in_sum_func)
        {
          /*
            Let upper function decide whether this field is a non
            aggregated one.
          */
          in_sum_func->outer_fields.push_back(field);
        }
        else
          sel->set_non_agg_field_used(true);
      }
      if (sel->nest_level > aggr_level &&
          (sel->agg_func_used()) &&
          !sel->group_list.elements)
      {
        my_message(ER_MIX_OF_GROUP_FUNC_AND_FIELDS,
                   ER(ER_MIX_OF_GROUP_FUNC_AND_FIELDS), MYF(0));
        return TRUE;
      }
    }
  }
  aggr_sel->set_agg_func_used(true);
  update_used_tables();
  thd->lex->in_sum_func= in_sum_func;
  return FALSE;
}

bool Item_sum::register_sum_func(THD *thd, Item **ref)
{
  nesting_map allow_sum_func= thd->lex->allow_sum_func;

  // Find the outer-most query block where this function can be aggregated.

  for (SELECT_LEX *sl= thd->lex->current_select->outer_select();
       sl && sl->nest_level >= max_arg_level;
       sl= sl->outer_select())
  {
    if (allow_sum_func & ((nesting_map)1 << sl->nest_level))
    {
      aggr_level= sl->nest_level;
      aggr_sel= sl;
    }
  }

  if (aggr_level >= 0)
  {
    ref_by= ref;
    /* Add the object to the list of registered objects assigned to aggr_sel */
    if (!aggr_sel->inner_sum_func_list)
      next= this;
    else
    {
      next= aggr_sel->inner_sum_func_list->next;
      aggr_sel->inner_sum_func_list->next= this;
    }
    aggr_sel->inner_sum_func_list= this;
    aggr_sel->with_sum_func= true;

    /* 
      Mark Item_subselect(s) as containing aggregate function all the way up
      to aggregate function's calculation context.
      Note that we must not mark the Item of calculation context itself
      because with_sum_func on the calculation context st_select_lex is
      already set above.

      with_sum_func being set for an Item means that this Item refers 
      (somewhere in it, e.g. one of its arguments if it's a function) directly
      or through intermediate items to an aggregate function that is calculated
      in a context "outside" of the Item (e.g. in the current or outer select).

      with_sum_func being set for an st_select_lex means that this query block
      has aggregate functions directly referenced (i.e. not through a subquery).
    */
    for (SELECT_LEX *sl= thd->lex->current_select; 
         sl && sl != aggr_sel && sl->master_unit()->item;
         sl= sl->outer_select())
      sl->master_unit()->item->with_sum_func= true;
  }
  thd->lex->current_select->mark_as_dependent(aggr_sel);
  return false;
}


Item_sum::Item_sum(List<Item> &list) :next(NULL), arg_count(list.elements), 
  forced_const(FALSE)
{
  if ((args=(Item**) sql_alloc(sizeof(Item*)*arg_count)))
  {
    uint i=0;
    List_iterator_fast<Item> li(list);
    Item *item;

    while ((item=li++))
    {
      args[i++]= item;
    }
  }
  if (!(orig_args= (Item **) sql_alloc(sizeof(Item *) * arg_count)))
  {
    args= NULL;
  }
  mark_as_sum_func();
  init_aggregator();
  list.empty();                                 // Fields are used
}


Item_sum::Item_sum(THD *thd, Item_sum *item):
  Item_result_field(thd, item),
  next(NULL),
  aggr_sel(item->aggr_sel),
  nest_level(item->nest_level), aggr_level(item->aggr_level),
  quick_group(item->quick_group),
  arg_count(item->arg_count), orig_args(NULL),
  used_tables_cache(item->used_tables_cache),
  forced_const(item->forced_const) 
{
  if (arg_count <= 2)
  {
    args=tmp_args;
    orig_args=tmp_orig_args;
  }
  else
  {
    if (!(args= (Item**) thd->alloc(sizeof(Item*)*arg_count)))
      return;
    if (!(orig_args= (Item**) thd->alloc(sizeof(Item*)*arg_count)))
      return;
  }
  memcpy(args, item->args, sizeof(Item*)*arg_count);
  memcpy(orig_args, item->orig_args, sizeof(Item*)*arg_count);
  init_aggregator();
  with_distinct= item->with_distinct;
  if (item->aggr)
    set_aggregator(item->aggr->Aggrtype());
}


void Item_sum::mark_as_sum_func()
{
  SELECT_LEX *cur_select= current_thd->lex->current_select;
  cur_select->n_sum_items++;
  cur_select->with_sum_func= 1;
  with_sum_func= 1;
}


void Item_sum::print(String *str, enum_query_type query_type)
{
  /* orig_args is not filled with valid values until fix_fields() */
  Item **pargs= fixed ? orig_args : args;
  str->append(func_name());
  for (uint i=0 ; i < arg_count ; i++)
  {
    if (i)
      str->append(',');
    pargs[i]->print(str, query_type);
  }
  str->append(')');
}

void Item_sum::fix_num_length_and_dec()
{
  decimals=0;
  for (uint i=0 ; i < arg_count ; i++)
    set_if_bigger(decimals,args[i]->decimals);
  max_length=float_length(decimals);
}

Item *Item_sum::get_tmp_table_item(THD *thd)
{
  Item_sum* sum_item= (Item_sum *) copy_or_same(thd);
  if (sum_item && sum_item->result_field)          // If not a const sum func
  {
    Field *result_field_tmp= sum_item->result_field;
    for (uint i=0 ; i < sum_item->arg_count ; i++)
    {
      Item *arg= sum_item->args[i];
      if (!arg->const_item())
      {
        if (arg->type() == Item::FIELD_ITEM)
          ((Item_field*) arg)->field= result_field_tmp++;
        else
          sum_item->args[i]= new Item_field(result_field_tmp++);
      }
    }
  }
  return sum_item;
}


bool Item_sum::walk (Item_processor processor, bool walk_subquery,
                     uchar *argument)
{
  if (arg_count)
  {
    Item **arg,**arg_end;
    for (arg= args, arg_end= args+arg_count; arg != arg_end; arg++)
    {
      if ((*arg)->walk(processor, walk_subquery, argument))
        return 1;
    }
  }
  return (this->*processor)(argument);
}


bool Item_sum::clean_up_after_removal(uchar *arg)
{
  /*
    Don't do anything if
    1) this is an unresolved item (This may happen if an
       expression occurs twice in the same query. In that case, the
       whole item tree for the second occurence is replaced by the
       item tree for the first occurence, without calling fix_fields()
       on the second tree. Therefore there's nothing to clean up.), or
    2) there is no inner_sum_func_list, or
    3) the item is not an element in the inner_sum_func_list.
  */
  if (!fixed ||                                                    // 1
      aggr_sel == NULL || aggr_sel->inner_sum_func_list == NULL || // 2
      next == NULL)                                                // 3
    return false;

  if (next == this)
    aggr_sel->inner_sum_func_list= NULL;
  else
  {
    Item_sum *prev;
    for (prev= this; prev->next != this; prev= prev->next)
      ;
    prev->next= next;
    if (aggr_sel->inner_sum_func_list == this)
      aggr_sel->inner_sum_func_list= prev;
  }

  return false;
}


Field *Item_sum::create_tmp_field(bool group, TABLE *table)
{
  Field *field;
  switch (result_type()) {
  case REAL_RESULT:
    field= new Field_double(max_length, maybe_null, item_name.ptr(), decimals, TRUE);
    break;
  case INT_RESULT:
    field= new Field_longlong(max_length, maybe_null, item_name.ptr(), unsigned_flag);
    break;
  case STRING_RESULT:
    return make_string_field(table);
  case DECIMAL_RESULT:
    field= Field_new_decimal::create_from_item(this);
    break;
  case ROW_RESULT:
  default:
    // This case should never be choosen
    DBUG_ASSERT(0);
    return 0;
  }
  if (field)
    field->init(table);
  return field;
}


void Item_sum::update_used_tables ()
{
  if (!forced_const)
  {
    used_tables_cache= 0;
    with_subselect= false;
    with_stored_program= false;
    for (uint i=0 ; i < arg_count ; i++)
    {
      args[i]->update_used_tables();
      used_tables_cache|= args[i]->used_tables();
      with_subselect|= args[i]->has_subquery();
      with_stored_program|= args[i]->has_stored_program();
    }

    used_tables_cache&= PSEUDO_TABLE_BITS;

    /* the aggregate function is aggregated into its local context */
    used_tables_cache|= ((table_map)1 << aggr_sel->join->tables) - 1;
  }
}


Item *Item_sum::set_arg(uint i, THD *thd, Item *new_val) 
{
  thd->change_item_tree(args + i, new_val);
  return new_val;
}


int Item_sum::set_aggregator(Aggregator::Aggregator_type aggregator)
{
  /*
    Dependent subselects may be executed multiple times, making
    set_aggregator to be called multiple times. The aggregator type
    will be the same, but it needs to be reset so that it is
    reevaluated with the new dependent data.
    This function may also be called multiple times during query optimization.
    In this case, the type may change, so we delete the old aggregator,
    and create a new one.
  */
  if (aggr && aggregator == aggr->Aggrtype())
  {
    aggr->clear();
    return FALSE;
  }

  delete aggr;
  switch (aggregator)
  {
  case Aggregator::DISTINCT_AGGREGATOR:
    aggr= new Aggregator_distinct(this);
    break;
  case Aggregator::SIMPLE_AGGREGATOR:
    aggr= new Aggregator_simple(this);
    break;
  };
  return aggr ? FALSE : TRUE;
}


void Item_sum::cleanup()
{
  if (aggr)
  {
    delete aggr;
    aggr= NULL;
  }
  Item_result_field::cleanup();
  forced_const= FALSE; 
}


static int simple_str_key_cmp(void* arg, uchar* key1, uchar* key2)
{
  Field *f= (Field*) arg;
  return f->cmp(key1, key2);
}


int Aggregator_distinct::composite_key_cmp(void* arg, uchar* key1, uchar* key2)
{
  Aggregator_distinct *aggr= (Aggregator_distinct *) arg;
  Field **field    = aggr->table->field;
  Field **field_end= field + aggr->table->s->fields;
  uint32 *lengths=aggr->field_lengths;
  for (; field < field_end; ++field)
  {
    Field* f = *field;
    int len = *lengths++;
    int res = f->cmp(key1, key2);
    if (res)
      return res;
    key1 += len;
    key2 += len;
  }
  return 0;
}


static enum enum_field_types 
calc_tmp_field_type(enum enum_field_types table_field_type, 
                    Item_result result_type)
{
  /* Adjust tmp table type according to the chosen aggregation type */
  switch (result_type) {
  case STRING_RESULT:
  case REAL_RESULT:
    if (table_field_type != MYSQL_TYPE_FLOAT)
      table_field_type= MYSQL_TYPE_DOUBLE;
    break;
  case INT_RESULT:
    table_field_type= MYSQL_TYPE_LONGLONG;
    /* fallthrough */
  case DECIMAL_RESULT:
    if (table_field_type != MYSQL_TYPE_LONGLONG)
      table_field_type= MYSQL_TYPE_NEWDECIMAL;
    break;
  case ROW_RESULT:
  default:
    DBUG_ASSERT(0);
  }
  return table_field_type;
}


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

C_MODE_START

/* Declarations for auxilary C-callbacks */

static int simple_raw_key_cmp(const void* arg,
                              const void* key1, const void* key2)
{
    return memcmp(key1, key2, *(const uint *) arg);
}


static int item_sum_distinct_walk(void *element, element_count num_of_dups,
                                  void *item)
{
  return ((Aggregator_distinct*) (item))->unique_walk_function(element);
}

C_MODE_END

/***************************************************************************/
bool Aggregator_distinct::setup(THD *thd)
{
  endup_done= FALSE;
  /*
    Setup can be called twice for ROLLUP items. This is a bug.
    Please add DBUG_ASSERT(tree == 0) here when it's fixed.
  */
  if (tree || table || tmp_table_param)
    return FALSE;

  if (item_sum->setup(thd))
    return TRUE;
  if (item_sum->sum_func() == Item_sum::COUNT_FUNC || 
      item_sum->sum_func() == Item_sum::COUNT_DISTINCT_FUNC)
  {
    List<Item> list;
    SELECT_LEX *select_lex= thd->lex->current_select;

    if (!(tmp_table_param= new TMP_TABLE_PARAM))
      return TRUE;

    /* Create a table with an unique key over all parameters */
    for (uint i=0; i < item_sum->get_arg_count() ; i++)
    {
      Item *item=item_sum->get_arg(i);
      if (list.push_back(item))
        return TRUE;                              // End of memory
      if (item->const_item() && item->is_null())
        always_null= true;
    }
    if (always_null)
      return FALSE;
    count_field_types(select_lex, tmp_table_param, list, 0);
    tmp_table_param->force_copy_fields= item_sum->has_force_copy_fields();
    DBUG_ASSERT(table == 0);
    /*
      Make create_tmp_table() convert BIT columns to BIGINT.
      This is needed because BIT fields store parts of their data in table's
      null bits, and we don't have methods to compare two table records, which
      is needed by Unique which is used when HEAP table is used.
    */
    {
      List_iterator_fast<Item> li(list);
      Item *item;
      while ((item= li++))
      {    
        if (item->type() == Item::FIELD_ITEM &&
            ((Item_field*)item)->field->type() == FIELD_TYPE_BIT)
          item->marker=4;
      }    
    }    
    if (!(table= create_tmp_table(thd, tmp_table_param, list, (ORDER*) 0, 1,
                                  0,
                                  (select_lex->options | thd->variables.option_bits),
                                  HA_POS_ERROR, "")))
      return TRUE;
    table->file->extra(HA_EXTRA_NO_ROWS);               // Don't update rows
    table->no_rows=1;

    if (table->s->db_type() == heap_hton)
    {
      /*
        No blobs, otherwise it would have been MyISAM: set up a compare
        function and its arguments to use with Unique.
      */
      qsort_cmp2 compare_key;
      void* cmp_arg;
      Field **field= table->field;
      Field **field_end= field + table->s->fields;
      bool all_binary= TRUE;

      for (tree_key_length= 0; field < field_end; ++field)
      {
        Field *f= *field;
        enum enum_field_types type= f->type();
        tree_key_length+= f->pack_length();
        if ((type == MYSQL_TYPE_VARCHAR) ||
            (!f->binary() && (type == MYSQL_TYPE_STRING ||
                             type == MYSQL_TYPE_VAR_STRING)))
        {
          all_binary= FALSE;
          break;
        }
      }
      if (all_binary)
      {
        cmp_arg= (void*) &tree_key_length;
        compare_key= (qsort_cmp2) simple_raw_key_cmp;
      }
      else
      {
        if (table->s->fields == 1)
        {
          /*
            If we have only one field, which is the most common use of
            count(distinct), it is much faster to use a simpler key
            compare method that can take advantage of not having to worry
            about other fields.
          */
          compare_key= (qsort_cmp2) simple_str_key_cmp;
          cmp_arg= (void*) table->field[0];
          /* tree_key_length has been set already */
        }
        else
        {
          uint32 *length;
          compare_key= (qsort_cmp2) composite_key_cmp;
          cmp_arg= (void*) this;
          field_lengths= (uint32*) thd->alloc(table->s->fields * sizeof(uint32));
          for (tree_key_length= 0, length= field_lengths, field= table->field;
               field < field_end; ++field, ++length)
          {
            *length= (*field)->pack_length();
            tree_key_length+= *length;
          }
        }
      }
      DBUG_ASSERT(tree == 0);
      tree= new Unique(compare_key, cmp_arg, tree_key_length,
                       item_sum->ram_limitation(thd));
      /*
        The only time tree_key_length could be 0 is if someone does
        count(distinct) on a char(0) field - stupid thing to do,
        but this has to be handled - otherwise someone can crash
        the server with a DoS attack
      */
      if (! tree)
        return TRUE;
    }
    return FALSE;
  }
  else
  {
    List<Create_field> field_list;
    Create_field field_def;                              /* field definition */
    Item *arg;
    DBUG_ENTER("Aggregator_distinct::setup");
    /* It's legal to call setup() more than once when in a subquery */
    if (tree)
      DBUG_RETURN(FALSE);

    /*
      Virtual table and the tree are created anew on each re-execution of
      PS/SP. Hence all further allocations are performed in the runtime
      mem_root.
    */
    if (field_list.push_back(&field_def))
      DBUG_RETURN(TRUE);

    item_sum->null_value= item_sum->maybe_null= 1;
    item_sum->quick_group= 0;

    DBUG_ASSERT(item_sum->get_arg(0)->fixed);

    arg= item_sum->get_arg(0);
    if (arg->const_item())
    {
      (void) arg->val_int();
      if (arg->null_value)
        always_null= true;
    }

    if (always_null)
      DBUG_RETURN(FALSE);

    enum enum_field_types field_type;

    field_type= calc_tmp_field_type(arg->field_type(),
                              arg->result_type());
    field_def.init_for_tmp_table(field_type, 
                                 arg->max_length,
                                 arg->decimals, 
                                 arg->maybe_null,
                                 arg->unsigned_flag);

    if (! (table= create_virtual_tmp_table(thd, field_list)))
      DBUG_RETURN(TRUE);

    /* XXX: check that the case of CHAR(0) works OK */
    tree_key_length= table->s->reclength - table->s->null_bytes;

    /*
      Unique handles all unique elements in a tree until they can't fit
      in.  Then the tree is dumped to the temporary file. We can use
      simple_raw_key_cmp because the table contains numbers only; decimals
      are converted to binary representation as well.
    */
    tree= new Unique(simple_raw_key_cmp, &tree_key_length, tree_key_length,
                     item_sum->ram_limitation(thd));

    DBUG_RETURN(tree == 0);
  }
}


void Aggregator_distinct::clear()
{
  endup_done= FALSE;
  item_sum->clear();
  if (tree)
    tree->reset();
  /* tree and table can be both null only if always_null */
  if (item_sum->sum_func() == Item_sum::COUNT_FUNC || 
      item_sum->sum_func() == Item_sum::COUNT_DISTINCT_FUNC)
  {
    if (!tree && table)
    {
      table->file->extra(HA_EXTRA_NO_CACHE);
      table->file->ha_delete_all_rows();
      table->file->extra(HA_EXTRA_WRITE_CACHE);
    }
  }
  else
  {
    item_sum->null_value= 1;
  }
}


bool Aggregator_distinct::add()
{
  if (always_null)
    return 0;

  if (item_sum->sum_func() == Item_sum::COUNT_FUNC || 
      item_sum->sum_func() == Item_sum::COUNT_DISTINCT_FUNC)
  {
    int error;
    copy_fields(tmp_table_param);
    if (copy_funcs(tmp_table_param->items_to_copy, table->in_use))
      return TRUE;

    for (Field **field=table->field ; *field ; field++)
      if ((*field)->is_real_null(0))
        return 0;                                       // Don't count NULL

    if (tree)
    {
      /*
        The first few bytes of record (at least one) are just markers
        for deleted and NULLs. We want to skip them since they will
        bloat the tree without providing any valuable info. Besides,
        key_length used to initialize the tree didn't include space for them.
      */
      return tree->unique_add(table->record[0] + table->s->null_bytes);
    }
    if ((error= table->file->ha_write_row(table->record[0])) &&
        table->file->is_fatal_error(error, HA_CHECK_DUP))
      return TRUE;
    return FALSE;
  }
  else
  {
    item_sum->get_arg(0)->save_in_field(table->field[0], FALSE);
    if (table->field[0]->is_null())
      return 0;
    DBUG_ASSERT(tree);
    item_sum->null_value= 0;
    /*
      '0' values are also stored in the tree. This doesn't matter
      for SUM(DISTINCT), but is important for AVG(DISTINCT)
    */
    return tree->unique_add(table->field[0]->ptr);
  }
}


void Aggregator_distinct::endup()
{
  /* prevent consecutive recalculations */
  if (endup_done)
    return;

  /* we are going to calculate the aggregate value afresh */
  item_sum->clear();

  /* The result will definitely be null : no more calculations needed */
  if (always_null)
    return;

  if (item_sum->sum_func() == Item_sum::COUNT_FUNC || 
      item_sum->sum_func() == Item_sum::COUNT_DISTINCT_FUNC)
  {
    DBUG_ASSERT(item_sum->fixed == 1);
    Item_sum_count *sum= (Item_sum_count *)item_sum;
    if (tree && tree->elements == 0)
    {
      /* everything fits in memory */
      sum->count= (longlong) tree->elements_in_tree();
      endup_done= TRUE;
    }
    if (!tree)
    {
      /* there were blobs */
      table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
      sum->count= table->file->stats.records;
      endup_done= TRUE;
    }
  }
  else
  {
    /*
      We don't have a tree only if 'setup()' hasn't been called;
      this is the case of sql_executor.cc:return_zero_rows.
    */
    if (tree)
      table->field[0]->set_notnull();
  }

  if (tree && !endup_done)
  {
    /* go over the tree of distinct keys and calculate the aggregate value */
    use_distinct_values= TRUE;
    tree->walk(item_sum_distinct_walk, (void*) this);
    use_distinct_values= FALSE;
  }
  /* prevent consecutive recalculations */
  endup_done= TRUE;
}


String *
Item_sum_num::val_str(String *str)
{
  return val_string_from_real(str);
}


my_decimal *Item_sum_num::val_decimal(my_decimal *decimal_value)
{
  return val_decimal_from_real(decimal_value);
}


String *
Item_sum_int::val_str(String *str)
{
  return val_string_from_int(str);
}


my_decimal *Item_sum_int::val_decimal(my_decimal *decimal_value)
{
  return val_decimal_from_int(decimal_value);
}


bool
Item_sum_num::fix_fields(THD *thd, Item **ref)
{
  DBUG_ASSERT(fixed == 0);

  if (init_sum_func_check(thd))
    return TRUE;

  decimals=0;
  maybe_null=0;
  for (uint i=0 ; i < arg_count ; i++)
  {
    if ((!args[i]->fixed && args[i]->fix_fields(thd, args + i)) ||
        args[i]->check_cols(1))
      return TRUE;
    set_if_bigger(decimals, args[i]->decimals);
    maybe_null |= args[i]->maybe_null;
  }
  result_field=0;
  max_length=float_length(decimals);
  null_value=1;
  fix_length_and_dec();

  if (check_sum_func(thd, ref))
    return TRUE;

  memcpy (orig_args, args, sizeof (Item *) * arg_count);
  fixed= 1;
  return FALSE;
}


bool
Item_sum_hybrid::fix_fields(THD *thd, Item **ref)
{
  DBUG_ASSERT(fixed == 0);

  Item *item= args[0];

  if (init_sum_func_check(thd))
    return TRUE;

  // 'item' can be changed during fix_fields
  if ((!item->fixed && item->fix_fields(thd, args)) ||
      (item= args[0])->check_cols(1))
    return TRUE;
  decimals=item->decimals;

  switch (hybrid_type= item->result_type()) {
  case INT_RESULT:
  case DECIMAL_RESULT:
  case STRING_RESULT:
    max_length= item->max_length;
    break;
  case REAL_RESULT:
    max_length= float_length(decimals);
    break;
  case ROW_RESULT:
  default:
    DBUG_ASSERT(0);
  };
  setup_hybrid(args[0], NULL);
  /* MIN/MAX can return NULL for empty set indepedent of the used column */
  maybe_null= 1;
  unsigned_flag=item->unsigned_flag;
  result_field=0;
  null_value=1;
  fix_length_and_dec();
  item= item->real_item();
  if (item->type() == Item::FIELD_ITEM)
    hybrid_field_type= ((Item_field*) item)->field->type();
  else
    hybrid_field_type= Item::field_type();

  if (check_sum_func(thd, ref))
    return TRUE;

  orig_args[0]= args[0];
  fixed= 1;
  return FALSE;
}


void Item_sum_hybrid::setup_hybrid(Item *item, Item *value_arg)
{
  value= Item_cache::get_cache(item);
  value->setup(item);
  value->store(value_arg);
  arg_cache= Item_cache::get_cache(item);
  arg_cache->setup(item);
  cmp= new Arg_comparator();
  cmp->set_cmp_func(this, (Item**)&arg_cache, (Item**)&value, FALSE);
  collation.set(item->collation);
}


Field *Item_sum_hybrid::create_tmp_field(bool group, TABLE *table)
{
  Field *field;
  if (args[0]->type() == Item::FIELD_ITEM)
  {
    field= ((Item_field*) args[0])->field;
    
    if ((field= create_tmp_field_from_field(current_thd, field, item_name.ptr(),
                                            table, NULL)))
      field->flags&= ~NOT_NULL_FLAG;
    return field;
  }
  /*
    DATE/TIME fields have STRING_RESULT result types.
    In order to preserve field type, it's needed to handle DATE/TIME
    fields creations separately.
  */
  switch (args[0]->field_type()) {
  case MYSQL_TYPE_DATE:
    field= new Field_newdate(maybe_null, item_name.ptr());
    break;
  case MYSQL_TYPE_TIME:
    field= new Field_timef(maybe_null, item_name.ptr(), decimals);
    break;
  case MYSQL_TYPE_TIMESTAMP:
  case MYSQL_TYPE_DATETIME:
    field= new Field_datetimef(maybe_null, item_name.ptr(), decimals);
    break;
  default:
    return Item_sum::create_tmp_field(group, table);
  }
  if (field)
    field->init(table);
  return field;
}


/***********************************************************************
** reset and add of sum_func
***********************************************************************/

Item_sum_sum::Item_sum_sum(THD *thd, Item_sum_sum *item) 
  :Item_sum_num(thd, item), hybrid_type(item->hybrid_type),
   curr_dec_buff(item->curr_dec_buff)
{
  /* TODO: check if the following assignments are really needed */
  if (hybrid_type == DECIMAL_RESULT)
  {
    my_decimal2decimal(item->dec_buffs, dec_buffs);
    my_decimal2decimal(item->dec_buffs + 1, dec_buffs + 1);
  }
  else
    sum= item->sum;
}

Item *Item_sum_sum::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_sum(thd, this);
}


void Item_sum_sum::clear()
{
  DBUG_ENTER("Item_sum_sum::clear");
  null_value=1;
  if (hybrid_type == DECIMAL_RESULT)
  {
    curr_dec_buff= 0;
    my_decimal_set_zero(dec_buffs);
  }
  else
    sum= 0.0;
  DBUG_VOID_RETURN;
}


void Item_sum_sum::fix_length_and_dec()
{
  DBUG_ENTER("Item_sum_sum::fix_length_and_dec");
  maybe_null=null_value=1;
  decimals= args[0]->decimals;
  switch (args[0]->numeric_context_result_type()) {
  case REAL_RESULT:
    hybrid_type= REAL_RESULT;
    sum= 0.0;
    break;
  case INT_RESULT:
  case DECIMAL_RESULT:
  {
    /* SUM result can't be longer than length(arg) + length(MAX_ROWS) */
    int precision= args[0]->decimal_precision() + DECIMAL_LONGLONG_DIGITS;
    max_length= my_decimal_precision_to_length_no_truncation(precision,
                                                             decimals,
                                                             unsigned_flag);
    curr_dec_buff= 0;
    hybrid_type= DECIMAL_RESULT;
    my_decimal_set_zero(dec_buffs);
    break;
  }
  case STRING_RESULT:
  case ROW_RESULT:
  default:
    DBUG_ASSERT(0);
  }
  DBUG_PRINT("info", ("Type: %s (%d, %d)",
                      (hybrid_type == REAL_RESULT ? "REAL_RESULT" :
                       hybrid_type == DECIMAL_RESULT ? "DECIMAL_RESULT" :
                       hybrid_type == INT_RESULT ? "INT_RESULT" :
                       "--ILLEGAL!!!--"),
                      max_length,
                      (int)decimals));
  DBUG_VOID_RETURN;
}


bool Item_sum_sum::add()
{
  DBUG_ENTER("Item_sum_sum::add");
  if (hybrid_type == DECIMAL_RESULT)
  {
    my_decimal value;
    const my_decimal *val= aggr->arg_val_decimal(&value);
    if (!aggr->arg_is_null())
    {
      my_decimal_add(E_DEC_FATAL_ERROR, dec_buffs + (curr_dec_buff^1),
                     val, dec_buffs + curr_dec_buff);
      curr_dec_buff^= 1;
      null_value= 0;
    }
  }
  else
  {
    sum+= aggr->arg_val_real();
    if (!aggr->arg_is_null())
      null_value= 0;
  }
  DBUG_RETURN(0);
}


longlong Item_sum_sum::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  if (hybrid_type == DECIMAL_RESULT)
  {
    longlong result;
    my_decimal2int(E_DEC_FATAL_ERROR, dec_buffs + curr_dec_buff, unsigned_flag,
                   &result);
    return result;
  }
  return (longlong) rint(val_real());
}


double Item_sum_sum::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  if (hybrid_type == DECIMAL_RESULT)
    my_decimal2double(E_DEC_FATAL_ERROR, dec_buffs + curr_dec_buff, &sum);
  return sum;
}


String *Item_sum_sum::val_str(String *str)
{
  if (aggr)
    aggr->endup();
  if (hybrid_type == DECIMAL_RESULT)
    return val_string_from_decimal(str);
  return val_string_from_real(str);
}


my_decimal *Item_sum_sum::val_decimal(my_decimal *val)
{
  if (aggr)
    aggr->endup();
  if (hybrid_type == DECIMAL_RESULT)
    return (dec_buffs + curr_dec_buff);
  return val_decimal_from_real(val);
}

bool Aggregator_distinct::unique_walk_function(void *element)
{
  memcpy(table->field[0]->ptr, element, tree_key_length);
  item_sum->add();
  return 0;
}


Aggregator_distinct::~Aggregator_distinct()
{
  if (tree)
  {
    delete tree;
    tree= NULL;
  }
  if (table)
  {
    free_tmp_table(table->in_use, table);
    table=NULL;
  }
  if (tmp_table_param)
  {
    delete tmp_table_param;
    tmp_table_param= NULL;
  }
}


my_decimal *Aggregator_simple::arg_val_decimal(my_decimal *value)
{
  return item_sum->args[0]->val_decimal(value);
}


double Aggregator_simple::arg_val_real()
{
  return item_sum->args[0]->val_real();
}


bool Aggregator_simple::arg_is_null()
{
  return item_sum->args[0]->null_value;
}


my_decimal *Aggregator_distinct::arg_val_decimal(my_decimal * value)
{
  return use_distinct_values ? table->field[0]->val_decimal(value) :
    item_sum->args[0]->val_decimal(value);
}


double Aggregator_distinct::arg_val_real()
{
  return use_distinct_values ? table->field[0]->val_real() :
    item_sum->args[0]->val_real();
}


bool Aggregator_distinct::arg_is_null()
{
  return use_distinct_values ? table->field[0]->is_null() :
    item_sum->args[0]->null_value;
}


Item *Item_sum_count::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_count(thd, this);
}


void Item_sum_count::clear()
{
  count= 0;
}


bool Item_sum_count::add()
{
  if (!args[0]->maybe_null || !args[0]->is_null())
    count++;
  return 0;
}

longlong Item_sum_count::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  return (longlong) count;
}


void Item_sum_count::cleanup()
{
  DBUG_ENTER("Item_sum_count::cleanup");
  count= 0;
  Item_sum_int::cleanup();
  DBUG_VOID_RETURN;
}


/*
  Avgerage
*/
void Item_sum_avg::fix_length_and_dec()
{
  Item_sum_sum::fix_length_and_dec();
  maybe_null=null_value=1;
  prec_increment= current_thd->variables.div_precincrement;
  if (hybrid_type == DECIMAL_RESULT)
  {
    int precision= args[0]->decimal_precision() + prec_increment;
    decimals= min<uint>(args[0]->decimals + prec_increment, DECIMAL_MAX_SCALE);
    max_length= my_decimal_precision_to_length_no_truncation(precision,
                                                             decimals,
                                                             unsigned_flag);
    f_precision= min(precision+DECIMAL_LONGLONG_DIGITS, DECIMAL_MAX_PRECISION);
    f_scale=  args[0]->decimals;
    dec_bin_size= my_decimal_get_binary_size(f_precision, f_scale);
  }
  else {
    decimals= min<uint>(args[0]->decimals + prec_increment, NOT_FIXED_DEC);
    max_length= args[0]->max_length + prec_increment;
  }
}


Item *Item_sum_avg::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_avg(thd, this);
}


Field *Item_sum_avg::create_tmp_field(bool group, TABLE *table)
{
  Field *field;
  if (group)
  {
    /*
      We must store both value and counter in the temporary table in one field.
      The easiest way is to do this is to store both value in a string
      and unpack on access.
    */
    field= new Field_string(((hybrid_type == DECIMAL_RESULT) ?
                             dec_bin_size : sizeof(double)) + sizeof(longlong),
                            0, item_name.ptr(), &my_charset_bin);
  }
  else if (hybrid_type == DECIMAL_RESULT)
    field= Field_new_decimal::create_from_item(this);
  else
    field= new Field_double(max_length, maybe_null, item_name.ptr(), decimals, TRUE);
  if (field)
    field->init(table);
  return field;
}


void Item_sum_avg::clear()
{
  Item_sum_sum::clear();
  count=0;
}


bool Item_sum_avg::add()
{
  if (Item_sum_sum::add())
    return TRUE;
  if (!aggr->arg_is_null())
    count++;
  return FALSE;
}

double Item_sum_avg::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  if (!count)
  {
    null_value=1;
    return 0.0;
  }
  return Item_sum_sum::val_real() / ulonglong2double(count);
}


my_decimal *Item_sum_avg::val_decimal(my_decimal *val)
{
  my_decimal sum_buff, cnt;
  const my_decimal *sum_dec;
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  if (!count)
  {
    null_value=1;
    return NULL;
  }

  /*
    For non-DECIMAL hybrid_type the division will be done in
    Item_sum_avg::val_real().
  */
  if (hybrid_type != DECIMAL_RESULT)
    return val_decimal_from_real(val);

  sum_dec= dec_buffs + curr_dec_buff;
  int2my_decimal(E_DEC_FATAL_ERROR, count, 0, &cnt);
  my_decimal_div(E_DEC_FATAL_ERROR, val, sum_dec, &cnt, prec_increment);
  return val;
}


String *Item_sum_avg::val_str(String *str)
{
  if (aggr)
    aggr->endup();
  if (hybrid_type == DECIMAL_RESULT)
    return val_string_from_decimal(str);
  return val_string_from_real(str);
}


/*
  Standard deviation
*/

double Item_sum_std::val_real()
{
  DBUG_ASSERT(fixed == 1);
  double nr= Item_sum_variance::val_real();
  DBUG_ASSERT(nr >= 0.0);
  return sqrt(nr);
}

Item *Item_sum_std::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_std(thd, this);
}


/*
  Variance
*/


/*
  These two functions are used by the Item_sum_variance and the
  Item_variance_field classes, which are unrelated, and each need to calculate
  variance.  The difference between the two classes is that the first is used
  for a mundane SELECT, while the latter is used in a GROUPing SELECT.
*/
static void variance_fp_recurrence_next(double *m, double *s, ulonglong *count, double nr)
{
  *count += 1;

  if (*count == 1) 
  {
    *m= nr;
    *s= 0;
  }
  else
  {
    double m_kminusone= *m;
    *m= m_kminusone + (nr - m_kminusone) / (double) *count;
    *s= *s + (nr - m_kminusone) * (nr - *m);
  }
}


static double variance_fp_recurrence_result(double s, ulonglong count, bool is_sample_variance)
{
  if (count == 1)
    return 0.0;

  if (is_sample_variance)
    return s / (count - 1);

  /* else, is a population variance */
  return s / count;
}


Item_sum_variance::Item_sum_variance(THD *thd, Item_sum_variance *item):
  Item_sum_num(thd, item), hybrid_type(item->hybrid_type),
    count(item->count), sample(item->sample),
    prec_increment(item->prec_increment)
{
  recurrence_m= item->recurrence_m;
  recurrence_s= item->recurrence_s;
}


void Item_sum_variance::fix_length_and_dec()
{
  DBUG_ENTER("Item_sum_variance::fix_length_and_dec");
  maybe_null= null_value= 1;

  /*
    According to the SQL2003 standard (Part 2, Foundations; sec 10.9,
    aggregate function; paragraph 7h of Syntax Rules), "the declared 
    type of the result is an implementation-defined aproximate numeric
    type.
  */
  hybrid_type= REAL_RESULT;
  decimals= NOT_FIXED_DEC;
  max_length= float_length(decimals);

  DBUG_PRINT("info", ("Type: REAL_RESULT (%d, %d)", max_length, (int)decimals));
  DBUG_VOID_RETURN;
}


Item *Item_sum_variance::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_variance(thd, this);
}


Field *Item_sum_variance::create_tmp_field(bool group, TABLE *table)
{
  Field *field;
  if (group)
  {
    /*
      We must store both value and counter in the temporary table in one field.
      The easiest way is to do this is to store both value in a string
      and unpack on access.
    */
    field= new Field_string(sizeof(double)*2 + sizeof(longlong), 0, item_name.ptr(), &my_charset_bin);
  }
  else
    field= new Field_double(max_length, maybe_null, item_name.ptr(), decimals, TRUE);

  if (field != NULL)
    field->init(table);

  return field;
}


void Item_sum_variance::clear()
{
  count= 0; 
}

bool Item_sum_variance::add()
{
  /* 
    Why use a temporary variable?  We don't know if it is null until we
    evaluate it, which has the side-effect of setting null_value .
  */
  double nr= args[0]->val_real();
  
  if (!args[0]->null_value)
    variance_fp_recurrence_next(&recurrence_m, &recurrence_s, &count, nr);
  return 0;
}

double Item_sum_variance::val_real()
{
  DBUG_ASSERT(fixed == 1);

  /*
    'sample' is a 1/0 boolean value.  If it is 1/true, id est this is a sample
    variance call, then we should set nullness when the count of the items
    is one or zero.  If it's zero, i.e. a population variance, then we only
    set nullness when the count is zero.

    Another way to read it is that 'sample' is the numerical threshhold, at and
    below which a 'count' number of items is called NULL.
  */
  DBUG_ASSERT((sample == 0) || (sample == 1));
  if (count <= sample)
  {
    null_value=1;
    return 0.0;
  }

  null_value=0;
  return variance_fp_recurrence_result(recurrence_s, count, sample);
}


my_decimal *Item_sum_variance::val_decimal(my_decimal *dec_buf)
{
  DBUG_ASSERT(fixed == 1);
  return val_decimal_from_real(dec_buf);
}


void Item_sum_variance::reset_field()
{
  double nr;
  uchar *res= result_field->ptr;

  nr= args[0]->val_real();              /* sets null_value as side-effect */

  if (args[0]->null_value)
    memset(res, 0, sizeof(double)*2+sizeof(longlong));
  else
  {
    /* Serialize format is (double)m, (double)s, (longlong)count */
    ulonglong tmp_count;
    double tmp_s;
    float8store(res, nr);               /* recurrence variable m */
    tmp_s= 0.0;
    float8store(res + sizeof(double), tmp_s);
    tmp_count= 1;
    int8store(res + sizeof(double)*2, tmp_count);
  }
}


void Item_sum_variance::update_field()
{
  ulonglong field_count;
  uchar *res=result_field->ptr;

  double nr= args[0]->val_real();       /* sets null_value as side-effect */

  if (args[0]->null_value)
    return;

  /* Serialize format is (double)m, (double)s, (longlong)count */
  double field_recurrence_m, field_recurrence_s;
  float8get(field_recurrence_m, res);
  float8get(field_recurrence_s, res + sizeof(double));
  field_count=sint8korr(res+sizeof(double)*2);

  variance_fp_recurrence_next(&field_recurrence_m, &field_recurrence_s, &field_count, nr);

  float8store(res, field_recurrence_m);
  float8store(res + sizeof(double), field_recurrence_s);
  res+= sizeof(double)*2;
  int8store(res,field_count);
}


/* min & max */

void Item_sum_hybrid::clear()
{
  value->clear();
  null_value= 1;
}

double Item_sum_hybrid::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0.0;
  double retval= value->val_real();
  if ((null_value= value->null_value))
    DBUG_ASSERT(retval == 0.0);
  return retval;
}

longlong Item_sum_hybrid::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0;
  longlong retval= value->val_int();
  if ((null_value= value->null_value))
    DBUG_ASSERT(retval == 0);
  return retval;
}


longlong Item_sum_hybrid::val_time_temporal()
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0;
  longlong retval= value->val_time_temporal();
  if ((null_value= value->null_value))
    DBUG_ASSERT(retval == 0);
  return retval;
}


longlong Item_sum_hybrid::val_date_temporal()
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0;
  longlong retval= value->val_date_temporal();
  if ((null_value= value->null_value))
    DBUG_ASSERT(retval == 0);
  return retval;
}


my_decimal *Item_sum_hybrid::val_decimal(my_decimal *val)
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0;
  my_decimal *retval= value->val_decimal(val);
  if ((null_value= value->null_value))
    DBUG_ASSERT(retval == NULL);
  return retval;
}


bool Item_sum_hybrid::get_date(MYSQL_TIME *ltime, uint fuzzydate)
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return true;
  return (null_value= value->get_date(ltime, fuzzydate));
}


bool Item_sum_hybrid::get_time(MYSQL_TIME *ltime)
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return true;
  return (null_value= value->get_time(ltime));
}


String *
Item_sum_hybrid::val_str(String *str)
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0;
  String *retval= value->val_str(str);
  if ((null_value= value->null_value))
    DBUG_ASSERT(retval == NULL);
  return retval;
}


void Item_sum_hybrid::cleanup()
{
  DBUG_ENTER("Item_sum_hybrid::cleanup");
  Item_sum::cleanup();
  forced_const= FALSE;
  if (cmp)
    delete cmp;
  cmp= 0;
  /*
    by default it is TRUE to avoid TRUE reporting by
    Item_func_not_all/Item_func_nop_all if this item was never called.

    no_rows_in_result() set it to FALSE if was not results found.
    If some results found it will be left unchanged.
  */
  was_values= TRUE;
  DBUG_VOID_RETURN;
}

void Item_sum_hybrid::no_rows_in_result()
{
  was_values= FALSE;
  clear();
}


Item *Item_sum_min::copy_or_same(THD* thd)
{
  Item_sum_min *item= new (thd->mem_root) Item_sum_min(thd, this);
  item->setup_hybrid(args[0], value);
  return item;
}


bool Item_sum_min::add()
{
  /* args[0] < value */
  arg_cache->cache_value();
  if (!arg_cache->null_value &&
      (null_value || cmp->compare() < 0))
  {
    value->store(arg_cache);
    value->cache_value();
    null_value= 0;
  }
  return 0;
}


Item *Item_sum_max::copy_or_same(THD* thd)
{
  Item_sum_max *item= new (thd->mem_root) Item_sum_max(thd, this);
  item->setup_hybrid(args[0], value);
  return item;
}


bool Item_sum_max::add()
{
  /* args[0] > value */
  arg_cache->cache_value();
  if (!arg_cache->null_value &&
      (null_value || cmp->compare() > 0))
  {
    value->store(arg_cache);
    value->cache_value();
    null_value= 0;
  }
  return 0;
}


/* bit_or and bit_and */

longlong Item_sum_bit::val_int()
{
  DBUG_ASSERT(fixed == 1);
  return (longlong) bits;
}


void Item_sum_bit::clear()
{
  bits= reset_bits;
}

Item *Item_sum_or::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_or(thd, this);
}


bool Item_sum_or::add()
{
  ulonglong value= (ulonglong) args[0]->val_int();
  if (!args[0]->null_value)
    bits|=value;
  return 0;
}

Item *Item_sum_xor::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_xor(thd, this);
}


bool Item_sum_xor::add()
{
  ulonglong value= (ulonglong) args[0]->val_int();
  if (!args[0]->null_value)
    bits^=value;
  return 0;
}

Item *Item_sum_and::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_and(thd, this);
}


bool Item_sum_and::add()
{
  ulonglong value= (ulonglong) args[0]->val_int();
  if (!args[0]->null_value)
    bits&=value;
  return 0;
}

/************************************************************************
** reset result of a Item_sum with is saved in a tmp_table
*************************************************************************/

void Item_sum_num::reset_field()
{
  double nr= args[0]->val_real();
  uchar *res=result_field->ptr;

  if (maybe_null)
  {
    if (args[0]->null_value)
    {
      nr=0.0;
      result_field->set_null();
    }
    else
      result_field->set_notnull();
  }
  float8store(res,nr);
}


void Item_sum_hybrid::reset_field()
{
  switch(hybrid_type) {
  case STRING_RESULT:
  {
    if (args[0]->is_temporal())
    {
      longlong nr= args[0]->val_temporal_by_field_type();
      if (maybe_null)
      {
        if (args[0]->null_value)
        {
          nr= 0;
          result_field->set_null();
        }
        else
          result_field->set_notnull();
      }
      result_field->store_packed(nr);
      break;
    }
    
    char buff[MAX_FIELD_WIDTH];
    String tmp(buff,sizeof(buff),result_field->charset()),*res;

    res=args[0]->val_str(&tmp);
    if (args[0]->null_value)
    {
      result_field->set_null();
      result_field->reset();
    }
    else
    {
      result_field->set_notnull();
      result_field->store(res->ptr(),res->length(),tmp.charset());
    }
    break;
  }
  case INT_RESULT:
  {
    longlong nr=args[0]->val_int();

    if (maybe_null)
    {
      if (args[0]->null_value)
      {
        nr=0;
        result_field->set_null();
      }
      else
        result_field->set_notnull();
    }
    result_field->store(nr, unsigned_flag);
    break;
  }
  case REAL_RESULT:
  {
    double nr= args[0]->val_real();

    if (maybe_null)
    {
      if (args[0]->null_value)
      {
        nr=0.0;
        result_field->set_null();
      }
      else
        result_field->set_notnull();
    }
    result_field->store(nr);
    break;
  }
  case DECIMAL_RESULT:
  {
    my_decimal value_buff, *arg_dec= args[0]->val_decimal(&value_buff);

    if (maybe_null)
    {
      if (args[0]->null_value)
        result_field->set_null();
      else
        result_field->set_notnull();
    }
    /*
      We must store zero in the field as we will use the field value in
      add()
    */
    if (!arg_dec)                               // Null
      arg_dec= &decimal_zero;
    result_field->store_decimal(arg_dec);
    break;
  }
  case ROW_RESULT:
  default:
    DBUG_ASSERT(0);
  }
}


void Item_sum_sum::reset_field()
{
  DBUG_ASSERT (aggr->Aggrtype() != Aggregator::DISTINCT_AGGREGATOR);
  if (hybrid_type == DECIMAL_RESULT)
  {
    my_decimal value, *arg_val= args[0]->val_decimal(&value);
    if (!arg_val)                               // Null
      arg_val= &decimal_zero;
    result_field->store_decimal(arg_val);
  }
  else
  {
    DBUG_ASSERT(hybrid_type == REAL_RESULT);
    double nr= args[0]->val_real();                     // Nulls also return 0
    float8store(result_field->ptr, nr);
  }
  if (args[0]->null_value)
    result_field->set_null();
  else
    result_field->set_notnull();
}


void Item_sum_count::reset_field()
{
  uchar *res=result_field->ptr;
  longlong nr=0;
  DBUG_ASSERT (aggr->Aggrtype() != Aggregator::DISTINCT_AGGREGATOR);

  if (!args[0]->maybe_null || !args[0]->is_null())
    nr=1;
  int8store(res,nr);
}


void Item_sum_avg::reset_field()
{
  uchar *res=result_field->ptr;
  DBUG_ASSERT (aggr->Aggrtype() != Aggregator::DISTINCT_AGGREGATOR);
  if (hybrid_type == DECIMAL_RESULT)
  {
    longlong tmp;
    my_decimal value, *arg_dec= args[0]->val_decimal(&value);
    if (args[0]->null_value)
    {
      arg_dec= &decimal_zero;
      tmp= 0;
    }
    else
      tmp= 1;
    my_decimal2binary(E_DEC_FATAL_ERROR, arg_dec, res, f_precision, f_scale);
    res+= dec_bin_size;
    int8store(res, tmp);
  }
  else
  {
    double nr= args[0]->val_real();

    if (args[0]->null_value)
      memset(res, 0, sizeof(double)+sizeof(longlong));
    else
    {
      longlong tmp= 1;
      float8store(res,nr);
      res+=sizeof(double);
      int8store(res,tmp);
    }
  }
}


void Item_sum_bit::reset_field()
{
  reset_and_add();
  int8store(result_field->ptr, bits);
}

void Item_sum_bit::update_field()
{
  uchar *res=result_field->ptr;
  bits= uint8korr(res);
  add();
  int8store(res, bits);
}


void Item_sum_sum::update_field()
{
  DBUG_ASSERT (aggr->Aggrtype() != Aggregator::DISTINCT_AGGREGATOR);
  if (hybrid_type == DECIMAL_RESULT)
  {
    my_decimal value, *arg_val= args[0]->val_decimal(&value);
    if (!args[0]->null_value)
    {
      if (!result_field->is_null())
      {
        my_decimal field_value,
                   *field_val= result_field->val_decimal(&field_value);
        my_decimal_add(E_DEC_FATAL_ERROR, dec_buffs, arg_val, field_val);
        result_field->store_decimal(dec_buffs);
      }
      else
      {
        result_field->store_decimal(arg_val);
        result_field->set_notnull();
      }
    }
  }
  else
  {
    double old_nr,nr;
    uchar *res=result_field->ptr;

    float8get(old_nr,res);
    nr= args[0]->val_real();
    if (!args[0]->null_value)
    {
      old_nr+=nr;
      result_field->set_notnull();
    }
    float8store(res,old_nr);
  }
}


void Item_sum_count::update_field()
{
  longlong nr;
  uchar *res=result_field->ptr;

  nr=sint8korr(res);
  if (!args[0]->maybe_null || !args[0]->is_null())
    nr++;
  int8store(res,nr);
}


void Item_sum_avg::update_field()
{
  longlong field_count;
  uchar *res=result_field->ptr;

  DBUG_ASSERT (aggr->Aggrtype() != Aggregator::DISTINCT_AGGREGATOR);

  if (hybrid_type == DECIMAL_RESULT)
  {
    my_decimal value, *arg_val= args[0]->val_decimal(&value);
    if (!args[0]->null_value)
    {
      binary2my_decimal(E_DEC_FATAL_ERROR, res,
                        dec_buffs + 1, f_precision, f_scale);
      field_count= sint8korr(res + dec_bin_size);
      my_decimal_add(E_DEC_FATAL_ERROR, dec_buffs, arg_val, dec_buffs + 1);
      my_decimal2binary(E_DEC_FATAL_ERROR, dec_buffs,
                        res, f_precision, f_scale);
      res+= dec_bin_size;
      field_count++;
      int8store(res, field_count);
    }
  }
  else
  {
    double nr;

    nr= args[0]->val_real();
    if (!args[0]->null_value)
    {
      double old_nr;
      float8get(old_nr, res);
      field_count= sint8korr(res + sizeof(double));
      old_nr+= nr;
      float8store(res,old_nr);
      res+= sizeof(double);
      field_count++;
      int8store(res, field_count);
    }
  }
}


void Item_sum_hybrid::update_field()
{
  switch (hybrid_type) {
  case STRING_RESULT:
    if (args[0]->is_temporal())
      min_max_update_temporal_field();
    else
      min_max_update_str_field();
    break;
  case INT_RESULT:
    min_max_update_int_field();
    break;
  case DECIMAL_RESULT:
    min_max_update_decimal_field();
    break;
  default:
    min_max_update_real_field();
  }
}


void Item_sum_hybrid::min_max_update_temporal_field()
{
  longlong nr, old_nr;
  old_nr= result_field->val_temporal_by_field_type();
  nr= args[0]->val_temporal_by_field_type();
  if (!args[0]->null_value)
  {
    if (result_field->is_null(0))
      old_nr= nr;
    else
    {
      bool res= unsigned_flag ?
                (ulonglong) old_nr > (ulonglong) nr : old_nr > nr;
      if ((cmp_sign > 0) ^ (!res))
        old_nr= nr;
    }
    result_field->set_notnull();
  }
  else if (result_field->is_null(0))
    result_field->set_null();
  result_field->store_packed(old_nr);
}


void Item_sum_hybrid::min_max_update_str_field()
{
  DBUG_ASSERT(cmp);
  String *res_str=args[0]->val_str(&cmp->value1);

  if (!args[0]->null_value)
  {
    result_field->val_str(&cmp->value2);

    if (result_field->is_null() ||
        (cmp_sign * sortcmp(res_str,&cmp->value2,collation.collation)) < 0)
      result_field->store(res_str->ptr(),res_str->length(),res_str->charset());
    result_field->set_notnull();
  }
}


void Item_sum_hybrid::min_max_update_real_field()
{
  double nr,old_nr;

  old_nr=result_field->val_real();
  nr= args[0]->val_real();
  if (!args[0]->null_value)
  {
    if (result_field->is_null(0) ||
        (cmp_sign > 0 ? old_nr > nr : old_nr < nr))
      old_nr=nr;
    result_field->set_notnull();
  }
  else if (result_field->is_null(0))
    result_field->set_null();
  result_field->store(old_nr);
}


void Item_sum_hybrid::min_max_update_int_field()
{
  longlong nr,old_nr;

  old_nr=result_field->val_int();
  nr=args[0]->val_int();
  if (!args[0]->null_value)
  {
    if (result_field->is_null(0))
      old_nr=nr;
    else
    {
      bool res=(unsigned_flag ?
                (ulonglong) old_nr > (ulonglong) nr :
                old_nr > nr);
      /* (cmp_sign > 0 && res) || (!(cmp_sign > 0) && !res) */
      if ((cmp_sign > 0) ^ (!res))
        old_nr=nr;
    }
    result_field->set_notnull();
  }
  else if (result_field->is_null(0))
    result_field->set_null();
  result_field->store(old_nr, unsigned_flag);
}


void Item_sum_hybrid::min_max_update_decimal_field()
{
  /* TODO: optimize: do not get result_field in case of args[0] is NULL */
  my_decimal old_val, nr_val;
  const my_decimal *old_nr= result_field->val_decimal(&old_val);
  const my_decimal *nr= args[0]->val_decimal(&nr_val);
  if (!args[0]->null_value)
  {
    if (result_field->is_null(0))
      old_nr=nr;
    else
    {
      bool res= my_decimal_cmp(old_nr, nr) > 0;
      /* (cmp_sign > 0 && res) || (!(cmp_sign > 0) && !res) */
      if ((cmp_sign > 0) ^ (!res))
        old_nr=nr;
    }
    result_field->set_notnull();
  }
  else if (result_field->is_null(0))
    result_field->set_null();
  result_field->store_decimal(old_nr);
}


Item_avg_field::Item_avg_field(Item_result res_type, Item_sum_avg *item)
{
  item_name= item->item_name;
  decimals=item->decimals;
  max_length= item->max_length;
  unsigned_flag= item->unsigned_flag;
  field=item->result_field;
  maybe_null=1;
  hybrid_type= res_type;
  prec_increment= item->prec_increment;
  if (hybrid_type == DECIMAL_RESULT)
  {
    f_scale= item->f_scale;
    f_precision= item->f_precision;
    dec_bin_size= item->dec_bin_size;
  }
}

double Item_avg_field::val_real()
{
  // fix_fields() never calls for this Item
  double nr;
  longlong count;
  uchar *res;

  if (hybrid_type == DECIMAL_RESULT)
    return val_real_from_decimal();

  float8get(nr,field->ptr);
  res= (field->ptr+sizeof(double));
  count= sint8korr(res);

  if ((null_value= !count))
    return 0.0;
  return nr/(double) count;
}


my_decimal *Item_avg_field::val_decimal(my_decimal *dec_buf)
{
  // fix_fields() never calls for this Item
  if (hybrid_type == REAL_RESULT)
    return val_decimal_from_real(dec_buf);

  longlong count= sint8korr(field->ptr + dec_bin_size);
  if ((null_value= !count))
    return 0;

  my_decimal dec_count, dec_field;
  binary2my_decimal(E_DEC_FATAL_ERROR,
                    field->ptr, &dec_field, f_precision, f_scale);
  int2my_decimal(E_DEC_FATAL_ERROR, count, 0, &dec_count);
  my_decimal_div(E_DEC_FATAL_ERROR, dec_buf,
                 &dec_field, &dec_count, prec_increment);
  return dec_buf;
}


String *Item_avg_field::val_str(String *str)
{
  // fix_fields() never calls for this Item
  if (hybrid_type == DECIMAL_RESULT)
    return val_string_from_decimal(str);
  return val_string_from_real(str);
}


Item_std_field::Item_std_field(Item_sum_std *item)
  : Item_variance_field(item)
{
}


double Item_std_field::val_real()
{
  double nr;
  // fix_fields() never calls for this Item
  nr= Item_variance_field::val_real();
  DBUG_ASSERT(nr >= 0.0);
  return sqrt(nr);
}


my_decimal *Item_std_field::val_decimal(my_decimal *dec_buf)
{
  /*
    We can't call val_decimal_from_real() for DECIMAL_RESULT as
    Item_variance_field::val_real() would cause an infinite loop
  */
  my_decimal tmp_dec, *dec;
  double nr;
  if (hybrid_type == REAL_RESULT)
    return val_decimal_from_real(dec_buf);

  dec= Item_variance_field::val_decimal(dec_buf);
  if (!dec)
    return 0;
  my_decimal2double(E_DEC_FATAL_ERROR, dec, &nr);
  DBUG_ASSERT(nr >= 0.0);
  nr= sqrt(nr);
  double2my_decimal(E_DEC_FATAL_ERROR, nr, &tmp_dec);
  my_decimal_round(E_DEC_FATAL_ERROR, &tmp_dec, decimals, FALSE, dec_buf);
  return dec_buf;
}


Item_variance_field::Item_variance_field(Item_sum_variance *item)
{
  item_name= item->item_name;
  decimals=item->decimals;
  max_length=item->max_length;
  unsigned_flag= item->unsigned_flag;
  field=item->result_field;
  maybe_null=1;
  sample= item->sample;
  prec_increment= item->prec_increment;
  if ((hybrid_type= item->hybrid_type) == DECIMAL_RESULT)
  {
    f_scale0= item->f_scale0;
    f_precision0= item->f_precision0;
    dec_bin_size0= item->dec_bin_size0;
    f_scale1= item->f_scale1;
    f_precision1= item->f_precision1;
    dec_bin_size1= item->dec_bin_size1;
  }
}


double Item_variance_field::val_real()
{
  // fix_fields() never calls for this Item
  if (hybrid_type == DECIMAL_RESULT)
    return val_real_from_decimal();

  double recurrence_s;
  ulonglong count;
  float8get(recurrence_s, (field->ptr + sizeof(double)));
  count=sint8korr(field->ptr+sizeof(double)*2);

  if ((null_value= (count <= sample)))
    return 0.0;

  return variance_fp_recurrence_result(recurrence_s, count, sample);
}


/****************************************************************************
** Functions to handle dynamic loadable aggregates
** Original source by: Alexis Mikhailov <root@medinf.chuvashia.su>
** Adapted for UDAs by: Andreas F. Bobak <bobak@relog.ch>.
** Rewritten by: Monty.
****************************************************************************/

#ifdef HAVE_DLOPEN

void Item_udf_sum::clear()
{
  DBUG_ENTER("Item_udf_sum::clear");
  udf.clear();
  DBUG_VOID_RETURN;
}

bool Item_udf_sum::add()
{
  DBUG_ENTER("Item_udf_sum::add");
  udf.add(&null_value);
  DBUG_RETURN(0);
}

void Item_udf_sum::cleanup()
{
  /*
    udf_handler::cleanup() nicely handles case when we have not
    original item but one created by copy_or_same() method.
  */
  udf.cleanup();
  Item_sum::cleanup();
}


void Item_udf_sum::print(String *str, enum_query_type query_type)
{
  str->append(func_name());
  str->append('(');
  for (uint i=0 ; i < arg_count ; i++)
  {
    if (i)
      str->append(',');
    args[i]->print(str, query_type);
  }
  str->append(')');
}


Item *Item_sum_udf_float::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_udf_float(thd, this);
}

double Item_sum_udf_float::val_real()
{
  DBUG_ASSERT(fixed == 1);
  DBUG_ENTER("Item_sum_udf_float::val");
  DBUG_PRINT("info",("result_type: %d  arg_count: %d",
                     args[0]->result_type(), arg_count));
  DBUG_RETURN(udf.val(&null_value));
}


String *Item_sum_udf_float::val_str(String *str)
{
  return val_string_from_real(str);
}


my_decimal *Item_sum_udf_float::val_decimal(my_decimal *dec)
{
  return val_decimal_from_real(dec);
}


String *Item_sum_udf_decimal::val_str(String *str)
{
  return val_string_from_decimal(str);
}


double Item_sum_udf_decimal::val_real()
{
  return val_real_from_decimal();
}


longlong Item_sum_udf_decimal::val_int()
{
  return val_int_from_decimal();
}


my_decimal *Item_sum_udf_decimal::val_decimal(my_decimal *dec_buf)
{
  DBUG_ASSERT(fixed == 1);
  DBUG_ENTER("Item_func_udf_decimal::val_decimal");
  DBUG_PRINT("info",("result_type: %d  arg_count: %d",
                     args[0]->result_type(), arg_count));

  DBUG_RETURN(udf.val_decimal(&null_value, dec_buf));
}


Item *Item_sum_udf_decimal::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_udf_decimal(thd, this);
}


Item *Item_sum_udf_int::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_udf_int(thd, this);
}

longlong Item_sum_udf_int::val_int()
{
  DBUG_ASSERT(fixed == 1);
  DBUG_ENTER("Item_sum_udf_int::val_int");
  DBUG_PRINT("info",("result_type: %d  arg_count: %d",
                     args[0]->result_type(), arg_count));
  DBUG_RETURN(udf.val_int(&null_value));
}


String *Item_sum_udf_int::val_str(String *str)
{
  return val_string_from_int(str);
}

my_decimal *Item_sum_udf_int::val_decimal(my_decimal *dec)
{
  return val_decimal_from_int(dec);
}


void Item_sum_udf_str::fix_length_and_dec()
{
  DBUG_ENTER("Item_sum_udf_str::fix_length_and_dec");
  max_length=0;
  for (uint i = 0; i < arg_count; i++)
    set_if_bigger(max_length,args[i]->max_length);
  DBUG_VOID_RETURN;
}


Item *Item_sum_udf_str::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_sum_udf_str(thd, this);
}


my_decimal *Item_sum_udf_str::val_decimal(my_decimal *dec)
{
  return val_decimal_from_string(dec);
}

String *Item_sum_udf_str::val_str(String *str)
{
  DBUG_ASSERT(fixed == 1);
  DBUG_ENTER("Item_sum_udf_str::str");
  String *res=udf.val_str(str,&str_value);
  null_value = !res;
  DBUG_RETURN(res);
}

#endif /* HAVE_DLOPEN */


/*****************************************************************************
 GROUP_CONCAT function

 SQL SYNTAX:
  GROUP_CONCAT([DISTINCT] expr,... [ORDER BY col [ASC|DESC],...]
    [SEPARATOR str_const])

 concat of values from "group by" operation

 BUGS
   Blobs doesn't work with DISTINCT or ORDER BY
*****************************************************************************/



extern "C"
int group_concat_key_cmp_with_distinct(const void* arg, const void* key1, 
                                       const void* key2)
{
  Item_func_group_concat *item_func= (Item_func_group_concat*)arg;
  TABLE *table= item_func->table;

  for (uint i= 0; i < item_func->arg_count_field; i++)
  {
    Item *item= item_func->args[i];
    /*
      If item is a const item then either get_tmp_table_field returns 0
      or it is an item over a const table.
    */
    if (item->const_item())
      continue;
    /*
      We have to use get_tmp_table_field() instead of
      real_item()->get_tmp_table_field() because we want the field in
      the temporary table, not the original field
    */
    Field *field= item->get_tmp_table_field();

    if (!field)
      continue;

    uint offset= field->offset(field->table->record[0])-table->s->null_bytes;
    int res= field->cmp((uchar*)key1 + offset, (uchar*)key2 + offset);
    if (res)
      return res;
  }
  return 0;
}


extern "C"
int group_concat_key_cmp_with_order(const void* arg, const void* key1, 
                                    const void* key2)
{
  const Item_func_group_concat* grp_item= (Item_func_group_concat*) arg;
  ORDER **order_item, **end;
  TABLE *table= grp_item->table;

  for (order_item= grp_item->order, end=order_item+ grp_item->arg_count_order;
       order_item < end;
       order_item++)
  {
    Item *item= *(*order_item)->item;
    /*
      If item is a const item then either get_tmp_table_field returns 0
      or it is an item over a const table.
    */
    if (item->const_item())
      continue;
    /*
      We have to use get_tmp_table_field() instead of
      real_item()->get_tmp_table_field() because we want the field in
      the temporary table, not the original field
     */
    Field *field= item->get_tmp_table_field();
    if (!field)
      continue;

    uint offset= (field->offset(field->table->record[0]) -
                  table->s->null_bytes);
    int res= field->cmp((uchar*)key1 + offset, (uchar*)key2 + offset);
    if (res)
      return ((*order_item)->direction == ORDER::ORDER_ASC) ? res : -res;
  }
  /*
    We can't return 0 because in that case the tree class would remove this
    item as double value. This would cause problems for case-changes and
    if the returned values are not the same we do the sort on.
  */
  return 1;
}


extern "C"
int dump_leaf_key(void* key_arg, element_count count __attribute__((unused)),
                  void* item_arg)
{
  Item_func_group_concat *item= (Item_func_group_concat *) item_arg;
  TABLE *table= item->table;
  String tmp((char *)table->record[1], table->s->reclength,
             default_charset_info);
  String tmp2;
  uchar *key= (uchar *) key_arg;
  String *result= &item->result;
  Item **arg= item->args, **arg_end= item->args + item->arg_count_field;
  uint old_length= result->length();

  if (item->no_appended)
    item->no_appended= FALSE;
  else
    result->append(*item->separator);

  tmp.length(0);

  for (; arg < arg_end; arg++)
  {
    String *res;
    /*
      We have to use get_tmp_table_field() instead of
      real_item()->get_tmp_table_field() because we want the field in
      the temporary table, not the original field
      We also can't use table->field array to access the fields
      because it contains both order and arg list fields.
     */
    if ((*arg)->const_item())
      res= (*arg)->val_str(&tmp);
    else
    {
      Field *field= (*arg)->get_tmp_table_field();
      if (field)
      {
        uint offset= (field->offset(field->table->record[0]) -
                      table->s->null_bytes);
        DBUG_ASSERT(offset < table->s->reclength);
        res= field->val_str(&tmp, key + offset);
      }
      else
        res= (*arg)->val_str(&tmp);
    }
    if (res)
      result->append(*res);
  }

  item->row_count++;

  /* stop if length of result more than max_length */
  if (result->length() > item->max_length)
  {
    int well_formed_error;
    const CHARSET_INFO *cs= item->collation.collation;
    const char *ptr= result->ptr();
    uint add_length;
    /*
      It's ok to use item->result.length() as the fourth argument
      as this is never used to limit the length of the data.
      Cut is done with the third argument.
    */
    add_length= cs->cset->well_formed_len(cs,
                                          ptr + old_length,
                                          ptr + item->max_length,
                                          result->length(),
                                          &well_formed_error);
    result->length(old_length + add_length);
    item->warning_for_row= TRUE;
    push_warning_printf(current_thd, Sql_condition::WARN_LEVEL_WARN,
                        ER_CUT_VALUE_GROUP_CONCAT, ER(ER_CUT_VALUE_GROUP_CONCAT),
                        item->row_count);

    if (table && table->blob_storage)
      table->blob_storage->set_truncated_value(false);
    return 1;
  }
  return 0;
}


Item_func_group_concat::
Item_func_group_concat(Name_resolution_context *context_arg,
                       bool distinct_arg, List<Item> *select_list,
                       const SQL_I_List<ORDER> &order_list,
                       String *separator_arg)
  :tmp_table_param(0), separator(separator_arg), tree(0),
   unique_filter(NULL), table(0),
   order(0), context(context_arg),
   arg_count_order(order_list.elements),
   arg_count_field(select_list->elements),
   row_count(0),
   distinct(distinct_arg),
   warning_for_row(FALSE),
   force_copy_fields(0), original(0)
{
  Item *item_select;
  Item **arg_ptr;

  quick_group= FALSE;
  arg_count= arg_count_field + arg_count_order;

  /*
    We need to allocate:
    args - arg_count_field+arg_count_order
           (for possible order items in temporare tables)
    order - arg_count_order
  */
  if (!(args= (Item**) sql_alloc(sizeof(Item*) * arg_count +
                                 sizeof(ORDER*)*arg_count_order)))
    return;

  if (!(orig_args= (Item **) sql_alloc(sizeof(Item *) * arg_count)))
  {
    args= NULL;
    return;
  }

  order= (ORDER**)(args + arg_count);

  /* fill args items of show and sort */
  List_iterator_fast<Item> li(*select_list);

  for (arg_ptr=args ; (item_select= li++) ; arg_ptr++)
    *arg_ptr= item_select;

  if (arg_count_order)
  {
    ORDER **order_ptr= order;
    for (ORDER *order_item= order_list.first;
         order_item != NULL;
         order_item= order_item->next)
    {
      (*order_ptr++)= order_item;
      *arg_ptr= *order_item->item;
      order_item->item= arg_ptr++;
    }
  }
  memcpy(orig_args, args, sizeof(Item*) * arg_count);
}


Item_func_group_concat::Item_func_group_concat(THD *thd,
                                               Item_func_group_concat *item)
  :Item_sum(thd, item),
  tmp_table_param(item->tmp_table_param),
  separator(item->separator),
  tree(item->tree),
  unique_filter(item->unique_filter),
  table(item->table),
  context(item->context),
  arg_count_order(item->arg_count_order),
  arg_count_field(item->arg_count_field),
  row_count(item->row_count),
  distinct(item->distinct),
  warning_for_row(item->warning_for_row),
  always_null(item->always_null),
  force_copy_fields(item->force_copy_fields),
  original(item)
{
  quick_group= item->quick_group;
  result.set_charset(collation.collation);

  /*
    Since the ORDER structures pointed to by the elements of the 'order' array
    may be modified in find_order_in_list() called from
    Item_func_group_concat::setup(), create a copy of those structures so that
    such modifications done in this object would not have any effect on the
    object being copied.
  */
  ORDER *tmp;
  if (!(order= (ORDER **) thd->alloc(sizeof(ORDER *) * arg_count_order +
                                     sizeof(ORDER) * arg_count_order)))
    return;
  tmp= (ORDER *)(order + arg_count_order);
  for (uint i= 0; i < arg_count_order; i++, tmp++)
  {
    /*
      Compiler generated copy constructor is used to
      to copy all the members of ORDER struct.
      It's also necessary to update ORDER::next pointer
      so that it points to new ORDER element.
    */
    new (tmp) st_order(*(item->order[i])); 
    tmp->next= (i + 1 == arg_count_order) ? NULL : (tmp + 1);
    order[i]= tmp;
  }
}



void Item_func_group_concat::cleanup()
{
  DBUG_ENTER("Item_func_group_concat::cleanup");
  Item_sum::cleanup();

  /*
    Free table and tree if they belong to this item (if item have not pointer
    to original item from which was made copy => it own its objects )
  */
  if (!original)
  {
    delete tmp_table_param;
    tmp_table_param= 0;
    if (table)
    {
      THD *thd= table->in_use;
      if (table->blob_storage)
        delete table->blob_storage;
      free_tmp_table(thd, table);
      table= 0;
      if (tree)
      {
        delete_tree(tree);
        tree= 0;
      }
      if (unique_filter)
      {
        delete unique_filter;
        unique_filter= NULL;
      }
    }
    DBUG_ASSERT(tree == 0);
  }
  DBUG_VOID_RETURN;
}


Field *Item_func_group_concat::make_string_field(TABLE *table)
{
  Field *field;
  DBUG_ASSERT(collation.collation);
  /*
    max_characters is maximum number of characters
    what can fit into max_length size. It's necessary
    to use field size what allows to store group_concat
    result without truncation. For this purpose we use
    max_characters * CS->mbmaxlen.
  */
  const uint32 max_characters= max_length / collation.collation->mbminlen;
  if (max_characters > CONVERT_IF_BIGGER_TO_BLOB)
    field= new Field_blob(max_characters * collation.collation->mbmaxlen,
                          maybe_null, item_name.ptr(), collation.collation, TRUE);
  else
    field= new Field_varstring(max_characters * collation.collation->mbmaxlen,
                               maybe_null, item_name.ptr(), table->s, collation.collation);

  if (field)
    field->init(table);
  return field;
}


Item *Item_func_group_concat::copy_or_same(THD* thd)
{
  return new (thd->mem_root) Item_func_group_concat(thd, this);
}


void Item_func_group_concat::clear()
{
  result.length(0);
  result.copy();
  null_value= TRUE;
  warning_for_row= FALSE;
  no_appended= TRUE;
  if (tree)
    reset_tree(tree);
  if (unique_filter)
    unique_filter->reset();
  if (table && table->blob_storage)
    table->blob_storage->reset();
  /* No need to reset the table as we never call write_row */
}


bool Item_func_group_concat::add()
{
  if (always_null)
    return 0;
  copy_fields(tmp_table_param);
  if (copy_funcs(tmp_table_param->items_to_copy, table->in_use))
    return TRUE;

  for (uint i= 0; i < arg_count_field; i++)
  {
    Item *show_item= args[i];
    if (show_item->const_item())
      continue;

    Field *field= show_item->get_tmp_table_field();
    if (field && field->is_null_in_record((const uchar*) table->record[0]))
        return 0;                               // Skip row if it contains null
  }

  null_value= FALSE;
  bool row_eligible= TRUE;

  if (distinct) 
  {
    /* Filter out duplicate rows. */
    uint count= unique_filter->elements_in_tree();
    unique_filter->unique_add(table->record[0] + table->s->null_bytes);
    if (count == unique_filter->elements_in_tree())
      row_eligible= FALSE;
  }

  TREE_ELEMENT *el= 0;                          // Only for safety
  if (row_eligible && tree)
  {
    DBUG_EXECUTE_IF("trigger_OOM_in_gconcat_add",
                     DBUG_SET("+d,simulate_persistent_out_of_memory"););
    el= tree_insert(tree, table->record[0] + table->s->null_bytes, 0,
                    tree->custom_arg);
    DBUG_EXECUTE_IF("trigger_OOM_in_gconcat_add",
                    DBUG_SET("-d,simulate_persistent_out_of_memory"););
    /* check if there was enough memory to insert the row */
    if (!el)
      return 1;
  }
  /*
    If the row is not a duplicate (el->count == 1)
    we can dump the row here in case of GROUP_CONCAT(DISTINCT...)
    instead of doing tree traverse later.
  */
  if (row_eligible && !warning_for_row &&
      (!tree || (el->count == 1 && distinct && !arg_count_order)))
    dump_leaf_key(table->record[0] + table->s->null_bytes, 1, this);

  return 0;
}


bool
Item_func_group_concat::fix_fields(THD *thd, Item **ref)
{
  uint i;                       /* for loop variable */
  DBUG_ASSERT(fixed == 0);

  if (init_sum_func_check(thd))
    return TRUE;

  maybe_null= 1;

  /*
    Fix fields for select list and ORDER clause
  */

  for (i=0 ; i < arg_count ; i++)
  {
    if ((!args[i]->fixed &&
         args[i]->fix_fields(thd, args + i)) ||
        args[i]->check_cols(1))
      return TRUE;
  }

  /* skip charset aggregation for order columns */
  if (agg_item_charsets_for_string_result(collation, func_name(),
                                          args, arg_count - arg_count_order))
    return 1;

  result.set_charset(collation.collation);
  result_field= 0;
  null_value= 1;
  max_length= thd->variables.group_concat_max_len;

  uint32 offset;
  if (separator->needs_conversion(separator->length(), separator->charset(),
                                  collation.collation, &offset))
  {
    uint32 buflen= collation.collation->mbmaxlen * separator->length();
    uint errors, conv_length;
    char *buf;
    String *new_separator;

    if (!(buf= (char*) thd->stmt_arena->alloc(buflen)) ||
        !(new_separator= new(thd->stmt_arena->mem_root)
                           String(buf, buflen, collation.collation)))
      return TRUE;
    
    conv_length= copy_and_convert(buf, buflen, collation.collation,
                                  separator->ptr(), separator->length(),
                                  separator->charset(), &errors);
    new_separator->length(conv_length);
    separator= new_separator;
  }

  if (check_sum_func(thd, ref))
    return TRUE;

  fixed= 1;
  return FALSE;
}


bool Item_func_group_concat::setup(THD *thd)
{
  List<Item> list;
  SELECT_LEX *select_lex= thd->lex->current_select;
  const bool order_or_distinct= test(arg_count_order > 0 || distinct);
  DBUG_ENTER("Item_func_group_concat::setup");

  /*
    Currently setup() can be called twice. Please add
    assertion here when this is fixed.
  */
  if (table || tree)
    DBUG_RETURN(FALSE);

  if (!(tmp_table_param= new TMP_TABLE_PARAM))
    DBUG_RETURN(TRUE);

  /* Push all not constant fields to the list and create a temp table */
  always_null= 0;
  for (uint i= 0; i < arg_count_field; i++)
  {
    Item *item= args[i];
    if (list.push_back(item))
      DBUG_RETURN(TRUE);
    if (item->const_item())
    {
      if (item->is_null())
      {
        always_null= 1;
        DBUG_RETURN(FALSE);
      }
    }
  }

  List<Item> all_fields(list);
  /*
    Try to find every ORDER expression in the list of GROUP_CONCAT
    arguments. If an expression is not found, prepend it to
    "all_fields". The resulting field list is used as input to create
    tmp table columns.
  */
  if (arg_count_order &&
      setup_order(thd, Ref_ptr_array(args, arg_count),
                  context->table_list, list, all_fields, *order))
    DBUG_RETURN(TRUE);

  count_field_types(select_lex, tmp_table_param, all_fields, 0);
  tmp_table_param->force_copy_fields= force_copy_fields;
  DBUG_ASSERT(table == 0);
  if (order_or_distinct)
  {
    /*
      Force the create_tmp_table() to convert BIT columns to INT
      as we cannot compare two table records containg BIT fields
      stored in the the tree used for distinct/order by.
      Moreover we don't even save in the tree record null bits 
      where BIT fields store parts of their data.
    */
    List_iterator_fast<Item> li(all_fields);
    Item *item;
    while ((item= li++))
    {
      if (item->type() == Item::FIELD_ITEM && 
          ((Item_field*) item)->field->type() == FIELD_TYPE_BIT)
        item->marker= 4;
    }
  }

  /*
    We have to create a temporary table to get descriptions of fields
    (types, sizes and so on).

    Note that in the table, we first have the ORDER BY fields, then the
    field list.
  */
  if (!(table= create_tmp_table(thd, tmp_table_param, all_fields,
                                (ORDER*) 0, 0, TRUE,
                                (select_lex->options | thd->variables.option_bits),
                                HA_POS_ERROR, (char*) "")))
    DBUG_RETURN(TRUE);
  table->file->extra(HA_EXTRA_NO_ROWS);
  table->no_rows= 1;

  if (order_or_distinct && table->s->blob_fields)
    table->blob_storage= new Blob_mem_storage();

  /*
     Need sorting or uniqueness: init tree and choose a function to sort.
     Don't reserve space for NULLs: if any of gconcat arguments is NULL,
     the row is not added to the result.
  */
  uint tree_key_length= table->s->reclength - table->s->null_bytes;

  if (arg_count_order)
  {
    tree= &tree_base;
    /*
      Create a tree for sorting. The tree is used to sort (according to the
      syntax of this function). If there is no ORDER BY clause, we don't
      create this tree.
    */
    init_tree(tree,  min<uint>(thd->variables.max_heap_table_size,
                               thd->variables.sortbuff_size/16), 0,
              tree_key_length, 
              group_concat_key_cmp_with_order , 0, NULL, (void*) this);
  }

  if (distinct)
    unique_filter= new Unique(group_concat_key_cmp_with_distinct,
                              (void*)this,
                              tree_key_length,
                              ram_limitation(thd));
  
  DBUG_RETURN(FALSE);
}


/* This is used by rollup to create a separate usable copy of the function */

void Item_func_group_concat::make_unique()
{
  tmp_table_param= 0;
  table=0;
  original= 0;
  force_copy_fields= 1;
  tree= 0;
}


String* Item_func_group_concat::val_str(String* str)
{
  DBUG_ASSERT(fixed == 1);
  if (null_value)
    return 0;
  if (no_appended && tree)
    /* Tree is used for sorting as in ORDER BY */
    tree_walk(tree, &dump_leaf_key, this, left_root_right);

  if (table && table->blob_storage && 
      table->blob_storage->is_truncated_value())
  {
    warning_for_row= true;
    push_warning_printf(current_thd, Sql_condition::WARN_LEVEL_WARN,
                        ER_CUT_VALUE_GROUP_CONCAT, ER(ER_CUT_VALUE_GROUP_CONCAT),
                        row_count);
  }

  return &result;
}


void Item_func_group_concat::print(String *str, enum_query_type query_type)
{
  str->append(STRING_WITH_LEN("group_concat("));
  if (distinct)
    str->append(STRING_WITH_LEN("distinct "));
  for (uint i= 0; i < arg_count_field; i++)
  {
    if (i)
      str->append(',');
    orig_args[i]->print(str, query_type);
  }
  if (arg_count_order)
  {
    str->append(STRING_WITH_LEN(" order by "));
    for (uint i= 0 ; i < arg_count_order ; i++)
    {
      if (i)
        str->append(',');
      orig_args[i + arg_count_field]->print(str, query_type);
      if (order[i]->direction == ORDER::ORDER_ASC)
        str->append(STRING_WITH_LEN(" ASC"));
      else
        str->append(STRING_WITH_LEN(" DESC"));
    }
  }
  str->append(STRING_WITH_LEN(" separator \'"));
  str->append(*separator);
  str->append(STRING_WITH_LEN("\')"));
}


Item_func_group_concat::~Item_func_group_concat()
{
  if (!original && unique_filter)
    delete unique_filter;    
}