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MDEV-17325 NULL-ability problems with LEAST() in combination with NO_ZERO_DATE and NO_ZERO_IN_DATE

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This commit is contained in:
Alexander Barkov
2018-09-29 21:20:24 +04:00
parent ad8e02ac45
commit 23740441d8
4 changed files with 284 additions and 0 deletions
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91
sql/sql_type.cc
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@ -3480,6 +3480,97 @@ bool Type_handler::
}
bool Type_handler_temporal_result::
Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
Item **items, uint nitems) const
{
bool rc= Type_handler::Item_func_min_max_fix_attributes(thd, func,
items, nitems);
if (rc || func->maybe_null)
return rc;
/*
LEAST/GREATES(non-temporal, temporal) can return NULL.
CAST functions Item_{time|datetime|date}_typecast always set maybe_full
to true. Here we try to detect nullability more thoroughly.
Perhaps CAST functions should also reuse this idea eventually.
*/
const Type_handler *hf= func->type_handler();
for (uint i= 0; i < nitems; i++)
{
/*
If items[i] does not need conversion to the current temporal data
type, then we trust items[i]->maybe_null, which was already ORred
to func->maybe_null in the argument loop in fix_fields().
If items[i] requires conversion to the current temporal data type,
then conversion can fail and return NULL even for NOT NULL items.
*/
const Type_handler *ha= items[i]->type_handler();
if (hf == ha)
continue; // No conversion.
if (ha->cmp_type() != TIME_RESULT)
{
func->maybe_null= true; // Conversion from non-temporal is not safe
break;
}
timestamp_type tf= hf->mysql_timestamp_type();
timestamp_type ta= ha->mysql_timestamp_type();
if (tf == ta ||
(tf == MYSQL_TIMESTAMP_DATETIME && ta == MYSQL_TIMESTAMP_DATE))
{
/*
If handlers have the same mysql_timestamp_type(),
then conversion is NULL safe. Conversion from DATE to DATETIME
is also safe. This branch includes data type pairs:
Function return type Argument type Comment
-------------------- ------------- -------------
TIMESTAMP TIMESTAMP no conversion
TIMESTAMP DATETIME not possible
TIMESTAMP DATE not possible
DATETIME DATETIME no conversion
DATETIME TIMESTAMP safe conversion
DATETIME DATE safe conversion
DATE DATE no conversion
TIME TIME no conversion
Note, a function cannot return TIMESTAMP if it has non-TIMESTAMP
arguments (it would return DATETIME in such case).
*/
DBUG_ASSERT(hf->field_type() != MYSQL_TYPE_TIMESTAMP || tf == ta);
continue;
}
/*
Here we have the following data type pairs that did not match
the condition above:
Function return type Argument type Comment
-------------------- ------------- -------
TIMESTAMP TIME Not possible
DATETIME TIME depends on OLD_MODE_ZERO_DATE_TIME_CAST
DATE TIMESTAMP Not possible
DATE DATETIME Not possible
DATE TIME Not possible
TIME TIMESTAMP Not possible
TIME DATETIME Not possible
TIME DATE Not possible
Most pairs are not possible, because the function data type
would be DATETIME (according to LEAST/GREATEST aggregation rules).
Conversion to DATETIME from TIME is not safe when
OLD_MODE_ZERO_DATE_TIME_CAST is set:
- negative TIME values cannot be converted to not-NULL DATETIME values
- TIME values can produce DATETIME values that do not pass
NO_ZERO_DATE and NO_ZERO_IN_DATE tests.
*/
DBUG_ASSERT(hf->field_type() == MYSQL_TYPE_DATETIME);
if (!(thd->variables.old_behavior & OLD_MODE_ZERO_DATE_TIME_CAST))
continue;
func->maybe_null= true;
break;
}
return rc;
}
bool Type_handler_real_result::
Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
Item **items, uint nitems) const