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Fix for BUG#16710.

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The bug was due to a missed case in the detection of whether an index
can be used for loose scan. More precisely, the range optimizer chose
to use loose index scan for queries for which the condition(s) over
an index key part could not be pushed to the index together with the
loose scan.

As a result, loose index scan was selecting the first row in the
index with a given GROUP BY prefix, and was applying the WHERE
clause after that, while it should have inspected all rows with
the given prefix, and apply the WHERE clause to all of them.

The fix detects and skips such cases.


mysql-test/r/group_min_max.result:
  Added test for BUG#16710.
mysql-test/t/group_min_max.test:
  Added test for BUG#16710.
sql/item.cc:
  Added new method [Item | Item_field]::find_item_in_field_list_processor.
sql/item.h:
  Added new method [Item | Item_field]::find_item_in_field_list_processor.
sql/opt_range.cc:
  Handle the case when there is no MIN/MAX aggregate function, and a
  keypart of the index being considered, that is after the GROUP BY
  prefix, is used in the WHERE clause and the condition where it is
  used cannot be pushed to the index.
  If this is the case, we rule out this index.
This commit is contained in:
unknown
2006-03-31 12:34:28 +03:00
parent 82f645531c
commit a01d48f92e
5 changed files with 78 additions and 1 deletions
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9
mysql-test/r/group_min_max.result
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@ -1954,6 +1954,15 @@ id select_type table type possible_keys key key_len ref rows Extra
explain select sum(ord(a1)) from t1 where (a1 > 'a') group by a1,a2,b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index idx_t1_0,idx_t1_1,idx_t1_2 idx_t1_1 163 NULL 128 Using where; Using index
explain select distinct(a1) from t1 where ord(a2) = 98;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL idx_t1_1 163 NULL 128 Using where; Using index
select distinct(a1) from t1 where ord(a2) = 98;
a1
a
b
c
d
explain select a1 from t1 where a2 = 'b' group by a1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL idx_t1_1 130 NULL 5 Using where; Using index for group-by