Hi Tor,
I'm afraid you're fixing the symptom instead of the problem.
Consider your test case:
SELECT 1 FROM t1 WHERE b < (SELECT CAST(a as date) FROM t1 GROUP BY a);
The problem seems to be this
1) Item_cache_datetime is created for item "cast (a as date)".
This is first evaluated by calling val_str() due to
Item_cache_datetime::result_type() == STRING_RESULT
#0 Item_cache_datetime::val_str (this=0x1ad3178, str=0x1af79f8)
at /mysql/mysql-5.5/sql/item.cc:7526
#1 0x00000000007f078f in Item_singlerow_subselect::val_str (this=0x1af79e8,
str=0x1af79f8)
at /mysql/mysql-5.5/sql/item_subselect.cc:605
#2 0x00000000007840d4 in Item::save_in_field (this=0x1af79e8,
field=0x1af8310, no_conversions=true)
at /mysql/mysql-5.5/sql/item.cc:5385
#3 0x000000000077796a in Item::save_in_field_no_warnings (this=0x1af79e8,
field=0x1af8310, no_conversions=true)
at /mysql/mysql-5.5/sql/item.cc:1062
2) The Item_cache_datetime above is compared to column b, which is of type INT.
stored_field_cmp_to_item() decides that STRING and INT comparisons should be
performed by using REAL. By calling Item_cache_datetime::val_real(),
Item_copy_string::val_int() is called:
#0 Item_copy_string::val_int (this=0x1ad5f08)
at /mysql/mysql-5.5/sql/item.cc:3596
#1 0x000000000056d611 in Item::val_int_result (this=0x1ad5f08)
at /mysql/mysql-5.5/sql/item.h:845
#2 0x000000000078ac98 in Item_cache_datetime::cache_value_int (this=0x1ad3178)
at /mysql/mysql-5.5/sql/item.cc:7477
#3 0x000000000078b3c7 in Item_cache_datetime::val_real (this=0x1ad3178)
at /mysql/mysql-5.5/sql/item.cc:7601
#4 0x00000000007f0605 in Item_singlerow_subselect::val_real (this=0x1af7a78)
at /mysql/mysql-5.5/sql/item_subselect.cc:576
#5 0x000000000078a586 in stored_field_cmp_to_item (thd=0x1a36dd0,
But Item_copy_string::val_int() uses my_strntoll() to convert the String
"2011-05-13" to an int. This does not work because my_strntoll() stops
processing when it encounters "-", so the resulting int is 2011 instead
of the expected 20110513. In addition, the call to cache_value_int() sets
str_value_cached=FALSE.
3) When Item_cache_datetime::val_str() is later called, str_value_cached=FALSE.
It tries to convert 2011 to a string using number_to_datetime(). This fails.
--
Jørgen Løland | Senior Software Engineer | +47 73842138
Oracle MySQL
Trondheim, Norway
