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Bug #42760: Select doesn't return desired results when we have null values

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Part 2 : 
There was a special optimization on the ref access method for 
ORDER BY ... DESC that was set without actually looking on the type of the 
selected index for ORDER BY.
Fixed the SELECT ... ORDER BY .. DESC (it uses a different code path compared
to the ASC that has been fixed with the previous fix).
This commit is contained in:
Georgi Kodinov 2009-12-07 16:38:56 +02:00
parent 36e019c933
commit bd308d1256
3 changed files with 19 additions and 1 deletions
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9
mysql-test/r/order_by.result
View File

@ -1111,5 +1111,14 @@ id select_type table type possible_keys key key_len ref rows Extra
SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c;
col
1
# Must use ref-or-null on the a_c index
EXPLAIN
SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c DESC;
id select_type table type possible_keys key key_len ref rows Extra
x x x ref_or_null a_c,a x x x x x
# Must return 1 row
SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c DESC;
col
1
DROP TABLE t1;
End of 5.0 tests

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

@ -778,6 +778,15 @@ SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c;
--echo # Must return 1 row
SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c;
# part 2 of the problem : DESC test cases
--echo # Must use ref-or-null on the a_c index
--replace_column 1 x 2 x 3 x 6 x 7 x 8 x 9 x 10 x
EXPLAIN
SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c DESC;
--echo # Must return 1 row
SELECT 1 AS col FROM t1 WHERE a=2 AND (c=10 OR c IS NULL) ORDER BY c DESC;
DROP TABLE t1;

2
sql/sql_select.cc
View File

@ -12824,7 +12824,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
}
DBUG_RETURN(1);
}
if (tab->ref.key_parts <= used_key_parts)
if (tab->ref.key_parts <= used_key_parts && tab->type == JT_REF)
{
/*
SELECT * FROM t1 WHERE a=1 ORDER BY a DESC,b DESC