Function update_ref_and_keys

sql/sql_select.cc:7714–7842

*/

static bool
update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
                    uint tables, COND *cond, table_map normal_tables,
                    SELECT_LEX *select_lex, SARGABLE_PARAM **sargables)
{
  uint	and_level,i;
  KEY_FIELD *key_fields, *end, *field;
  size_t sz;
  uint m= MY_MAX(select_lex->max_equal_elems,1);
  DBUG_ENTER("update_ref_and_keys");
  DBUG_PRINT("enter", ("normal_tables: %llx", normal_tables));

  SELECT_LEX *sel=thd->lex->current_select; 
  sel->cond_count= 0;
  sel->between_count= 0; 
  if (cond)
    cond->walk(&Item::count_sargable_conds, sel, 0);
  for (i=0 ; i < tables ; i++)
  {
    if (*join_tab[i].on_expr_ref)
      (*join_tab[i].on_expr_ref)->walk(&Item::count_sargable_conds, sel, 0);
  }
  {
    List_iterator<TABLE_LIST> li(*join_tab->join->join_list);
    TABLE_LIST *table;
    while ((table= li++))
    {
      if (table->nested_join)
        count_cond_for_nj(sel, table);
    }
  }
  
  /* 
    We use the same piece of memory to store both  KEY_FIELD 
    and SARGABLE_PARAM structure.
    KEY_FIELD values are placed at the beginning this memory
    while  SARGABLE_PARAM values are put at the end.
    All predicates that are used to fill arrays of KEY_FIELD
    and SARGABLE_PARAM structures have at most 2 arguments
    except BETWEEN predicates that have 3 arguments and 
    IN predicates.
    This any predicate if it's not BETWEEN/IN can be used 
    directly to fill at most 2 array elements, either of KEY_FIELD
    or SARGABLE_PARAM type. For a BETWEEN predicate 3 elements
    can be filled as this predicate is considered as
    sargable with respect to each of its argument.
    An IN predicate can require at most 1 element as currently
    it is considered as sargable only for its first argument.
    Multiple equality can add  elements that are filled after
    substitution of field arguments by equal fields. There
    can be not more than select_lex->max_equal_elems such 
    substitutions.
  */ 
  sz= MY_MAX(sizeof(KEY_FIELD),sizeof(SARGABLE_PARAM))*
    ((sel->cond_count*2 + sel->between_count)*m+1);
  if (!(key_fields=(KEY_FIELD*)	thd->alloc(sz)))
    DBUG_RETURN(TRUE); /* purecov: inspected */
  and_level= 0;