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Commit 221ce922 authored by Ole John Aske's avatar Ole John Aske
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Fix for bug#59308: Incorrect result for SELECT DISTINCT <col>... ORDER BY <col> DESC. 

      
Also fix bug#59110: Memory leak of QUICK_SELECT_I allocated memory.
Includes Jørgen Lølands review comments.
      
Root cause of these bugs are that test_if_skip_sort_order() decided to
revert the 'skip_sort_order' descision (and use filesort) after the
query plan has been updated to reflect a 'skip' of the sort order.
      
This might happen in 'check_reverse_order:' if we have a 
select->quick which could not be made descending by appending 
a QUICK_SELECT_DESC. ().
      
The original 'save_quick' was then restored after the QEP has been modified,
which caused:
      
  - An incorrect 'precomputed_group_by= TRUE' may have been set, 
    and not reverted, as part of the already modifified QEP (Bug#59308)
  - A 'select->quick' might have been created which we fail to delete (bug#59110).
      
This fix is a refactorication of test_if_skip_sort_order() where all logic
related to modification of QEP (controlled by argument 'bool no_changes'), is
moved to the end of test_if_skip_sort_order(), and done after *all* 'test_if_skip'
checks has been performed - including the 'check_reverse_order:' checks.
      
The refactorication above contains now intentional changes to the logic which 
has been moved to the end of the function.
      
Furthermore, a smaller part of the fix address the handling of the 
select->quick objects which may already exists when we call 
'test_if_skip_sort_order()' (save_quick) -and
new select->quick's created during test_if_skip_sort_order():
      
  - Before new select->quick may be created by calling ::test_quick_select(), we
    set 'select->quick= 0' to avoid that ::test_quick_select() prematurely
    delete the save_quick's. (After this call we may have both a 'save_quick' 
    and 'select->quick')
      
  - All returns from ::test_if_skip_sort_order() where we may have both a
    'save_quick' and a 'select->quick' has been changed to goto's to the
    exit points 'skiped_sort_order:' or 'need_filesort:' where we
    decide which of the QUICK_SELECT's to keep, and delete the other.
parent e29b40f8
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Showing with 177 additions and 88 deletions
mysql-test/r/order_by.result
View file @ 221ce922
......@@ -1638,4 +1638,29 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL a 8 NULL 10 Using index; Using temporary; Using filesort
1 SIMPLE t2 eq_ref PRIMARY PRIMARY 4 test.t1.b 1 Using where
DROP TABLE t1, t2;
#
# Bug #59110: Memory leak of QUICK_SELECT_I allocated memory
# and
# Bug #59308: Incorrect result for
SELECT DISTINCT <col>... ORDER BY <col> DESC
# Use Valgrind to detect #59110!
#
CREATE TABLE t1 (a INT,KEY (a));
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
EXPLAIN SELECT DISTINCT a,1 FROM t1 WHERE a <> 1 ORDER BY a DESC;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index a a 5 NULL 10 Using where; Using index; Using filesort
SELECT DISTINCT a,1 FROM t1 WHERE a <> 1 ORDER BY a DESC;
a 1
10 1
9 1
8 1
7 1
6 1
5 1
4 1
3 1
2 1
DROP TABLE t1;
End of 5.1 tests
mysql-test/t/order_by.test
View file @ 221ce922
......@@ -1492,4 +1492,21 @@ LIMIT 2;
DROP TABLE t1, t2;
--echo #
--echo # Bug #59110: Memory leak of QUICK_SELECT_I allocated memory
--echo # and
--echo # Bug #59308: Incorrect result for
--echo SELECT DISTINCT <col>... ORDER BY <col> DESC
--echo
--echo # Use Valgrind to detect #59110!
--echo #
CREATE TABLE t1 (a INT,KEY (a));
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
EXPLAIN SELECT DISTINCT a,1 FROM t1 WHERE a <> 1 ORDER BY a DESC;
SELECT DISTINCT a,1 FROM t1 WHERE a <> 1 ORDER BY a DESC;
DROP TABLE t1;
--echo End of 5.1 tests
sql/sql_select.cc
View file @ 221ce922
......@@ -13364,12 +13364,14 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
{
int ref_key;
uint ref_key_parts;
int order_direction;
int order_direction= 0;
uint used_key_parts;
TABLE *table=tab->table;
SQL_SELECT *select=tab->select;
key_map usable_keys;
QUICK_SELECT_I *save_quick= 0;
int best_key= -1;
DBUG_ENTER("test_if_skip_sort_order");
LINT_INIT(ref_key_parts);
......@@ -13473,13 +13475,14 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
new_ref_key_map.clear_all(); // Force the creation of quick select
new_ref_key_map.set_bit(new_ref_key); // only for new_ref_key.
select->quick= 0;
if (select->test_quick_select(tab->join->thd, new_ref_key_map, 0,
(tab->join->select_options &
OPTION_FOUND_ROWS) ?
HA_POS_ERROR :
tab->join->unit->select_limit_cnt,0) <=
0)
DBUG_RETURN(0);
goto use_filesort;
}
ref_key= new_ref_key;
}
......@@ -13504,7 +13507,6 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
int best_key_direction= 0;
ha_rows best_records= 0;
double read_time;
int best_key= -1;
bool is_best_covering= FALSE;
double fanout= 1;
JOIN *join= tab->join;
......@@ -13681,72 +13683,21 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
tab->join->tables > tab->join->const_tables + 1) &&
((unsigned) best_key != table->s->primary_key ||
!table->file->primary_key_is_clustered()))
DBUG_RETURN(0);
goto use_filesort;
if (best_key >= 0)
{
bool quick_created= FALSE;
if (table->quick_keys.is_set(best_key) && best_key != ref_key)
{
key_map map;
map.clear_all(); // Force the creation of quick select
map.set_bit(best_key); // only best_key.
quick_created=
select->test_quick_select(join->thd, map, 0,
join->select_options & OPTION_FOUND_ROWS ?
HA_POS_ERROR :
join->unit->select_limit_cnt,
0) > 0;
}
if (!no_changes)
{
/*
If ref_key used index tree reading only ('Using index' in EXPLAIN),
and best_key doesn't, then revert the decision.
*/
if (!table->covering_keys.is_set(best_key))
table->set_keyread(FALSE);
if (!quick_created)
{
tab->index= best_key;
tab->read_first_record= best_key_direction > 0 ?
join_read_first:join_read_last;
tab->type=JT_NEXT; // Read with index_first(), index_next()
if (select && select->quick)
{
delete select->quick;
select->quick= 0;
}
if (table->covering_keys.is_set(best_key))
table->set_keyread(TRUE);
table->file->ha_index_or_rnd_end();
if (join->select_options & SELECT_DESCRIBE)
{
tab->ref.key= -1;
tab->ref.key_parts= 0;
if (select_limit < table_records)
tab->limit= select_limit;
}
}
else if (tab->type != JT_ALL)
{
/*
We're about to use a quick access to the table.
We need to change the access method so as the quick access
method is actually used.
*/
DBUG_ASSERT(tab->select->quick);
tab->type=JT_ALL;
tab->use_quick=1;
tab->ref.key= -1;
tab->ref.key_parts=0; // Don't use ref key.
tab->read_first_record= join_init_read_record;
if (tab->is_using_loose_index_scan())
join->tmp_table_param.precomputed_group_by= TRUE;
/*
TODO: update the number of records in join->best_positions[tablenr]
*/
}
select->quick= 0;
select->test_quick_select(join->thd, map, 0,
join->select_options & OPTION_FOUND_ROWS ?
HA_POS_ERROR :
join->unit->select_limit_cnt,
0);
}
order_direction= best_key_direction;
/*
......@@ -13759,10 +13710,12 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
saved_best_key_parts : best_key_parts;
}
else
DBUG_RETURN(0);
goto use_filesort;
}
check_reverse_order:
DBUG_ASSERT(order_direction != 0);
if (order_direction == -1) // If ORDER BY ... DESC
{
if (select && select->quick)
......@@ -13771,9 +13724,10 @@ check_reverse_order:
Don't reverse the sort order, if it's already done.
(In some cases test_if_order_by_key() can be called multiple times
*/
if (!select->quick->reverse_sorted())
if (select->quick->reverse_sorted())
goto skipped_filesort;
else
{
QUICK_SELECT_DESC *tmp;
int quick_type= select->quick->get_type();
if (quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_MERGE ||
quick_type == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT ||
......@@ -13781,39 +13735,132 @@ check_reverse_order:
quick_type == QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX)
{
tab->limit= 0;
select->quick= save_quick;
DBUG_RETURN(0); // Use filesort
goto use_filesort; // Use filesort
}
/* ORDER BY range_key DESC */
tmp= new QUICK_SELECT_DESC((QUICK_RANGE_SELECT*)(select->quick),
used_key_parts);
if (!tmp || tmp->error)
{
delete tmp;
select->quick= save_quick;
tab->limit= 0;
DBUG_RETURN(0); // Reverse sort not supported
}
select->quick=tmp;
}
}
else if (tab->type != JT_NEXT && tab->type != JT_REF_OR_NULL &&
tab->ref.key >= 0 && tab->ref.key_parts <= used_key_parts)
}
/*
Update query plan with access pattern for doing
ordered access according to what we have decided
above.
*/
if (!no_changes) // We are allowed to update QEP
{
if (best_key >= 0)
{
/*
SELECT * FROM t1 WHERE a=1 ORDER BY a DESC,b DESC
bool quick_created=
(select && select->quick && select->quick!=save_quick);
Use a traversal function that starts by reading the last row
with key part (A) and then traverse the index backwards.
/*
If ref_key used index tree reading only ('Using index' in EXPLAIN),
and best_key doesn't, then revert the decision.
*/
tab->read_first_record= join_read_last_key;
tab->read_record.read_record= join_read_prev_same;
if (!table->covering_keys.is_set(best_key))
table->set_keyread(FALSE);
if (!quick_created)
{
if (select) // Throw any existing quick select
select->quick= 0; // Cleanup either reset to save_quick,
// or 'delete save_quick'
tab->index= best_key;
tab->read_first_record= order_direction > 0 ?
join_read_first:join_read_last;
tab->type=JT_NEXT; // Read with index_first(), index_next()
if (table->covering_keys.is_set(best_key))
table->set_keyread(TRUE);
table->file->ha_index_or_rnd_end();
if (tab->join->select_options & SELECT_DESCRIBE)
{
tab->ref.key= -1;
tab->ref.key_parts= 0;
if (select_limit < table->file->stats.records)
tab->limit= select_limit;
}
}
else if (tab->type != JT_ALL)
{
/*
We're about to use a quick access to the table.
We need to change the access method so as the quick access
method is actually used.
*/
DBUG_ASSERT(tab->select->quick);
tab->type=JT_ALL;
tab->use_quick=1;
tab->ref.key= -1;
tab->ref.key_parts=0; // Don't use ref key.
tab->read_first_record= join_init_read_record;
if (tab->is_using_loose_index_scan())
tab->join->tmp_table_param.precomputed_group_by= TRUE;
/*
TODO: update the number of records in join->best_positions[tablenr]
*/
}
} // best_key >= 0
if (order_direction == -1) // If ORDER BY ... DESC
{
if (select && select->quick)
{
QUICK_SELECT_DESC *tmp;
/* ORDER BY range_key DESC */
tmp= new QUICK_SELECT_DESC((QUICK_RANGE_SELECT*)(select->quick),
used_key_parts);
if (tmp && select->quick == save_quick)
save_quick= 0; // ::QUICK_SELECT_DESC consumed it
if (!tmp || tmp->error)
{
delete tmp;
tab->limit= 0;
goto use_filesort; // Reverse sort failed -> filesort
}
select->quick= tmp;
}
else if (tab->type != JT_NEXT && tab->type != JT_REF_OR_NULL &&
tab->ref.key >= 0 && tab->ref.key_parts <= used_key_parts)
{
/*
SELECT * FROM t1 WHERE a=1 ORDER BY a DESC,b DESC
Use a traversal function that starts by reading the last row
with key part (A) and then traverse the index backwards.
*/
tab->read_first_record= join_read_last_key;
tab->read_record.read_record= join_read_prev_same;
}
}
else if (select && select->quick)
select->quick->sorted= 1;
} // QEP has been modified
/*
Cleanup:
We may have both a 'select->quick' and 'save_quick' (original)
at this point. Delete the one that we wan't use.
*/
skipped_filesort:
// Keep current (ordered) select->quick
if (select && save_quick != select->quick)
{
delete save_quick;
save_quick= NULL;
}
else if (select && select->quick)
select->quick->sorted= 1;
DBUG_RETURN(1);
use_filesort:
// Restore original save_quick
if (select && select->quick != save_quick)
{
delete select->quick;
select->quick= save_quick;
}
DBUG_RETURN(0);
}
......
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