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Bug #30715: Assertion failed: item_field->field->real_maybe_null(),

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file .\opt_sum.cc, line
The optimizer pre-calculates the MIN/MAX values for queries like
 SELECT MIN(kp_k) WHERE kp_1 = const AND ... AND kp_k-1 = const
when there is a key over kp_1...kp_k
In doing so it was not checking correctly nullability and 
there was a superfluous assert(). 
Fixed by making sure that the field can be null before checking and
taking out the wrong assert().
.
Introduced a correct check for nullability 
The MIN(field) can return NULL when all the row values in the group
are NULL-able or if there were no rows.
Fixed the assertion to reflect the case when there are no rows.


mysql-test/r/func_group.result:
  Bug #30715: test case
mysql-test/t/func_group.test:
  Bug #30715: test case
sql/opt_sum.cc:
  Bug #30715: correct nullability check for MIN/MAX pre-calculation over index.
This commit is contained in:
unknown
2007-10-24 11:15:08 +03:00
parent 62a7e160bc
commit e2433cbcaa
3 changed files with 19 additions and 5 deletions
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5
mysql-test/r/func_group.result
View File

@ -1387,4 +1387,9 @@ SELECT 1 FROM t1 GROUP BY (SELECT SLEEP(0) FROM t1 ORDER BY AVG(DISTINCT a) );
1
1
DROP TABLE t1;
CREATE TABLE t1 (a int, b date NOT NULL, KEY k1 (a,b));
SELECT MIN(b) FROM t1 WHERE a=1 AND b>'2007-08-01';
MIN(b)
NULL
DROP TABLE t1;
End of 5.0 tests

9
mysql-test/t/func_group.test
View File

@ -873,5 +873,14 @@ SELECT 1 FROM t1 GROUP BY (SELECT SLEEP(0) FROM t1 ORDER BY AVG(DISTINCT a) );
DROP TABLE t1;
#
# Bug #30715: Assertion failed: item_field->field->real_maybe_null(), file
# .\opt_sum.cc, line
#
CREATE TABLE t1 (a int, b date NOT NULL, KEY k1 (a,b));
SELECT MIN(b) FROM t1 WHERE a=1 AND b>'2007-08-01';
DROP TABLE t1;
###
--echo End of 5.0 tests

4
sql/opt_sum.cc
View File

@ -249,7 +249,8 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
Check if case 1 from above holds. If it does, we should read
the skipped tuple.
*/
if (ref.key_buff[prefix_len] == 1 &&
if (item_field->field->real_maybe_null() &&
ref.key_buff[prefix_len] == 1 &&
/*
Last keypart (i.e. the argument to MIN) is set to NULL by
find_key_for_maxmin only if all other keyparts are bound
@ -260,7 +261,6 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
(error == HA_ERR_KEY_NOT_FOUND ||
key_cmp_if_same(table, ref.key_buff, ref.key, prefix_len)))
{
DBUG_ASSERT(item_field->field->real_maybe_null());
error= table->file->index_read(table->record[0], ref.key_buff,
ref.key_length,
HA_READ_KEY_EXACT);