EXPLAIN
SELECT COUNT(*)FROM dig_lotes WHERE lote_tipo='r' AND sit_spa!='mov'  

EXPLAIN
SELECT COUNT(*)FROM dig_lotes WHERE lote_tipo='r' AND sit_spa IN ('','d','s','p','a')

WHERE a != 10

WHERE a < 10 OR a > 10

  /* 
	MDEV-4419
	IMPOSSIBLE WHERE FOR ENUM FIELDS / REWRITE OF ENUM FIELDS OPERATOR
	
	any enum_field OP const_value should be executed in all enum values,
	to optimize the query, since ENUM is a 'bitmap' of all possible values
	we can rewrited it to IN/NOT IN operator, this allow index usage
	
	examples:
	
	for NULL possible fields:
		a ENUM ('a','b','c')
		internally we have: NULL,0=>'',1=>'a',2=>'b',3=>'c'
	for NOT NULL fields:
		a ENUM ('a','b','c') NOT NULL
		internally we have: 0=>'',1=>'a',2=>'b',3=>'c'
	
	example 1) (impossible where)
	WHERE a = 'd'
	'' = 'd'  ? false
	'a' = 'd' ? false
	'b' = 'd' ? false
	'c' = 'd' ? false
	
	rewrite to  
	(1=0) - always false, impossble where
	
	example 2) (allways true)
	a < 'd' will result:
	'' < 'd'  ? true
	'a' < 'd' ? true
	'b' < 'd' ? true
	'c' < 'd' ? true
	
	rewriting to :
	a IN ('','a','b','c') - always true
	
	example 3) (some values of enum, using IN)
	a LIKE '%a' will result:
	'' LIKE '%a'  ? false
	'a' LIKE '%a' ? true
	'b' LIKE '%a' ? false
	'c' LIKE '%a' ? false

	we have 1 true, and 3 falses, better use IN ()
	rewriting to :
	
	using IN:     a IN ('a')
	using NOT IN: a NOT IN ('','b','c')
	or using ENUM INDEX:
	using IN:     a IN (1)
	using NOT IN: a NOT IN (0,2,3)
	
	
	example 4) (some values of enum, using NOT IN)
	a != 'b' will result:
	'' != 'b'  ? true
	'a' != 'b' ? true
	'b' != 'b' ? false
	'c' != 'b' ? true
	
	we have 3 true, and 1 false, better use NOT IN ()
	rewriting to:
	
	using IN:     a IN ('','a','c')
	using NOT IN: a NOT IN ('b')
	or using ENUM INDEX:
	using IN:     a IN (0,1,3)
	using NOT IN: a NOT IN (2)
  */
  if (field->real_type() == MYSQL_TYPE_ENUM)
  {
    uint count_true_list =0;
    uint count_false_list=0;
    bool true_false_list[];
    uint enum_field_counter=0;
    char buffer[255];
    String enum_item(buffer, sizeof(buffer), res.charset());
    
    /* seek all values and check how many true/false we got */
    resize_true_false_list[]
    set true_false_list to false;
    /* true_false_list start from 0 to enum values +1, NULL = index 0, */
    uint *len= field->typelib->type_lengths;
    for (enum_field_counter=0,const char **pos= field->typelib->type_names; *pos; pos++, len++, enum_field_counter++)
    {
      enum_string_value= enum_item.copy(*pos, *len, charset(), res.charset(), &dummy_errors);
      if (type == Item_func::IN_FUNC)
      {
	/* search in each IN value */
	while( .. in_values .. )
	{

  	  if ((enum_str_value == in_str_value && in_value_is_string && compare_function(enum_str,in_str)) || 
              (enum_int_value == in_int_value && !in_value_is_string && compare_function(enum_int,in_int))) {
	    count_true_list ++;
	    true_false_list[enum_field_counter]=true;
 	  } else {
	    count_false_list ++;
	  }
	}
      } else if (type == Item_func::BETWEEN) {
        /* two args */
        // don't know what to do...
        goto end;
      } else {
        /* only one value */
  	if ((enum_str_value == str_value && value_is_string && compare_function(enum_str,value_str)) || 
              (enum_int_value == int_value && !value_is_string && compare_function(enum_int,value_int))) {
	  count_true_list ++;
	  true_false_list[enum_field_counter]=true;
	} else {
	  count_false_list ++;
	}
      }
    }
    /* check about always true (discart operation) / false (impossible where) */
    if (count_false_list == 0)
    {
      tree= &null_element;	/* always true */
      goto end;
    }
    if (count_true_list == 0)
    {
      tree->type= SEL_ARG::IMPOSSIBLE;	/* impossible where */
      goto end;
    }
    /* rewrite the operation using IN / NOT IN () */
    if (count_false_list > count_true_list)
	inv=true; /* add NOT before IN () */
    type=Item_func::IN_FUNC;
    for each true_false_list
    {
      if(inv)  
        add respective enum_value of true_false_list when it's false
      else
        add respective enum_value of true_false_list when it's true
    }
    goto end;
  }