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Bug#23800: Outer fields in correlated subqueries is used in a temporary table

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created for sorting.

Any outer reference in a subquery was represented by an Item_field object.
If the outer select employs a temporary table all such fields should be
replaced with fields from that temporary table in order to point to the 
actual data. This replacement wasn't done and that resulted in a wrong
subquery evaluation and a wrong result of the whole query.

Now any outer field is represented by two objects - Item_field placed in the
outer select and Item_outer_ref in the subquery. Item_field object is
processed as a normal field and the reference to it is saved in the
ref_pointer_array. Thus the Item_outer_ref is always references the correct
field. The original field is substituted for a reference in the
Item_field::fix_outer_field() function.

New function called fix_inner_refs() is added to fix fields referenced from
inner selects and to fix references (Item_ref objects) to these fields.

The new Item_outer_ref class is a descendant of the Item_direct_ref class.
It additionally stores a reference to the original field and designed to
behave more like a field.
This commit is contained in:
evgen@moonbone.local
2007-02-21 23:00:32 +03:00
parent 674868dabf
commit 9a233742b8
11 changed files with 290 additions and 41 deletions
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83
sql/sql_select.cc
View File

@ -268,6 +268,70 @@ bool handle_select(THD *thd, LEX *lex, select_result *result,
}
/*
Fix fields referenced from inner selects.
SYNOPSIS
fix_inner_refs()
thd Thread handle
all_fields List of all fields used in select
select Current select
ref_pointer_array Array of references to Items used in current select
DESCRIPTION
The function fixes fields referenced from inner selects and
also fixes references (Item_ref objects) to these fields. Each field
is fixed as a usual hidden field of the current select - it is added
to the all_fields list and the pointer to it is saved in the
ref_pointer_array if latter is provided.
After the field has been fixed we proceed with fixing references
(Item_ref objects) to this field from inner subqueries. If the
ref_pointer_array is provided then Item_ref objects is set to
reference element in that array with the pointer to the field.
RETURN
TRUE an error occured
FALSE ok
*/
bool
fix_inner_refs(THD *thd, List<Item> &all_fields, SELECT_LEX *select,
Item **ref_pointer_array)
{
Item_outer_ref *ref;
bool res= FALSE;
List_iterator<Item_outer_ref> ref_it(select->inner_refs_list);
while ((ref= ref_it++))
{
Item_field *item= ref->outer_field;
/*
TODO: this field item already might be present in the select list.
In this case instead of adding new field item we could use an
existing one. The change will lead to less operations for copying fields,
smaller temporary tables and less data passed through filesort.
*/
if (ref_pointer_array)
{
int el= all_fields.elements;
ref_pointer_array[el]= (Item*)item;
/* Add the field item to the select list of the current select. */
all_fields.push_front((Item*)item);
/*
If it's needed reset each Item_ref item that refers this field with
a new reference taken from ref_pointer_array.
*/
ref->ref= ref_pointer_array + el;
}
if (!ref->fixed && ref->fix_fields(thd, 0))
{
res= TRUE;
break;
}
thd->used_tables|= item->used_tables();
}
return res;
}
/*
Function to setup clauses without sum functions
*/
@ -395,6 +459,10 @@ JOIN::prepare(Item ***rref_pointer_array,
if (having && having->with_sum_func)
having->split_sum_func2(thd, ref_pointer_array, all_fields,
&having, TRUE);
if (select_lex->inner_refs_list.elements &&
fix_inner_refs(thd, all_fields, select_lex, ref_pointer_array))
DBUG_RETURN(-1);
if (select_lex->inner_sum_func_list)
{
Item_sum *end=select_lex->inner_sum_func_list;
@ -5133,13 +5201,15 @@ get_store_key(THD *thd, KEYUSE *keyuse, table_map used_tables,
key_part->length,
keyuse->val);
}
else if (keyuse->val->type() == Item::FIELD_ITEM)
else if (keyuse->val->type() == Item::FIELD_ITEM ||
(keyuse->val->type() == Item::REF_ITEM &&
((Item_ref*)keyuse->val)->ref_type() == Item_ref::OUTER_REF) )
return new store_key_field(thd,
key_part->field,
key_buff + maybe_null,
maybe_null ? key_buff : 0,
key_part->length,
((Item_field*) keyuse->val)->field,
((Item_field*) keyuse->val->real_item())->field,
keyuse->val->full_name());
return new store_key_item(thd,
key_part->field,
@ -8697,7 +8767,8 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
type they needed to be handled separately.
*/
if ((type= item->field_type()) == MYSQL_TYPE_DATETIME ||
type == MYSQL_TYPE_TIME || type == MYSQL_TYPE_DATE)
type == MYSQL_TYPE_TIME || type == MYSQL_TYPE_DATE ||
type == MYSQL_TYPE_TIMESTAMP)
new_field= item->tmp_table_field_from_field_type(table);
/*
Make sure that the blob fits into a Field_varstring which has
@ -8804,8 +8875,7 @@ Field *create_tmp_field(THD *thd, TABLE *table,Item *item, Item::Type type,
Item *orig_item= 0;
if (type != Item::FIELD_ITEM &&
item->real_item()->type() == Item::FIELD_ITEM &&
!((Item_ref *) item)->depended_from)
item->real_item()->type() == Item::FIELD_ITEM)
{
orig_item= item;
item= item->real_item();
@ -13465,8 +13535,7 @@ count_field_types(TMP_TABLE_PARAM *param, List<Item> &fields,
{
Item::Type type=field->type();
Item::Type real_type= field->real_item()->type();
if (type == Item::FIELD_ITEM || (real_type == Item::FIELD_ITEM &&
!((Item_ref *) field)->depended_from))
if (real_type == Item::FIELD_ITEM)
param->field_count++;
else if (real_type == Item::SUM_FUNC_ITEM)
{