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MDEV-40698 ROLLUP query returns incorrect result with empty result set #5542

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MDEV-40698 ROLLUP query returns incorrect result with empty result set #5542

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54 changes: 54 additions & 0 deletions mysql-test/main/mdev_40698.result
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Original file line number Diff line number Diff line change
@@ -0,0 +1,54 @@
#
# MDEV-40698: ROLLUP query returns incorrect result with empty result set
#
CREATE TABLE t0(a INT, b INT, c INT);
SELECT *, COUNT(0) FROM t0 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0)
NULL NULL NULL 0
SELECT *, COUNT(0) FROM t0 WHERE 1=0 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0)
NULL NULL NULL 0
SELECT *, COUNT(0), ROW_NUMBER() OVER () FROM t0 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0) ROW_NUMBER() OVER ()
NULL NULL NULL 0 1
SELECT 1 IN (SELECT a FROM t0 WHERE a>0 GROUP BY a WITH ROLLUP);
1 IN (SELECT a FROM t0 WHERE a>0 GROUP BY a WITH ROLLUP)
NULL
INSERT INTO t0 VALUES (0, 0, 0),(0, 0, 0);
SELECT *, COUNT(0) FROM t0 WHERE a > 0 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0)
NULL NULL NULL 0
SELECT EXISTS (SELECT t0.a FROM t0 x WHERE 1=0 GROUP BY x.a WITH ROLLUP) AS e
FROM t0;
e
1
1
SELECT DISTINCT a FROM t0 GROUP BY a, b WITH ROLLUP;
a
0
NULL
CREATE TABLE t1 (a INT, b INT, c INT) ENGINE=InnoDB;
SELECT *, COUNT(0) FROM t1 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0)
NULL NULL NULL 0
SELECT *, COUNT(0) FROM t1 WHERE 1=0 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0)
NULL NULL NULL 0
SELECT *, COUNT(0), ROW_NUMBER() OVER () FROM t1 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0) ROW_NUMBER() OVER ()
NULL NULL NULL 0 1
INSERT INTO t1 VALUES (0, 0, 0),(0, 0, 0);
SELECT *, COUNT(0) FROM t1 WHERE a > 0 GROUP BY a, b, c WITH ROLLUP;
a b c COUNT(0)
NULL NULL NULL 0
SELECT EXISTS (SELECT t1.a FROM t1 x WHERE 1=0 GROUP BY x.a WITH ROLLUP) AS e
FROM t1;
e
1
1
SELECT DISTINCT a FROM t1 GROUP BY a, b WITH ROLLUP;
a
0
NULL
DROP TABLE t0, t1;
# End of 10.11 tests
30 changes: 30 additions & 0 deletions mysql-test/main/mdev_40698.test
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@@ -0,0 +1,30 @@
--source include/have_innodb.inc

Comment thread
jaeheonshim marked this conversation as resolved.
--echo #
--echo # MDEV-40698: ROLLUP query returns incorrect result with empty result set
--echo #

CREATE TABLE t0(a INT, b INT, c INT);
SELECT *, COUNT(0) FROM t0 GROUP BY a, b, c WITH ROLLUP;
SELECT *, COUNT(0) FROM t0 WHERE 1=0 GROUP BY a, b, c WITH ROLLUP;
SELECT *, COUNT(0), ROW_NUMBER() OVER () FROM t0 GROUP BY a, b, c WITH ROLLUP;
SELECT 1 IN (SELECT a FROM t0 WHERE a>0 GROUP BY a WITH ROLLUP);
INSERT INTO t0 VALUES (0, 0, 0),(0, 0, 0);
SELECT *, COUNT(0) FROM t0 WHERE a > 0 GROUP BY a, b, c WITH ROLLUP;
SELECT EXISTS (SELECT t0.a FROM t0 x WHERE 1=0 GROUP BY x.a WITH ROLLUP) AS e
FROM t0;
SELECT DISTINCT a FROM t0 GROUP BY a, b WITH ROLLUP;

CREATE TABLE t1 (a INT, b INT, c INT) ENGINE=InnoDB;
SELECT *, COUNT(0) FROM t1 GROUP BY a, b, c WITH ROLLUP;
SELECT *, COUNT(0) FROM t1 WHERE 1=0 GROUP BY a, b, c WITH ROLLUP;
SELECT *, COUNT(0), ROW_NUMBER() OVER () FROM t1 GROUP BY a, b, c WITH ROLLUP;
INSERT INTO t1 VALUES (0, 0, 0),(0, 0, 0);
SELECT *, COUNT(0) FROM t1 WHERE a > 0 GROUP BY a, b, c WITH ROLLUP;
SELECT EXISTS (SELECT t1.a FROM t1 x WHERE 1=0 GROUP BY x.a WITH ROLLUP) AS e
FROM t1;
SELECT DISTINCT a FROM t1 GROUP BY a, b WITH ROLLUP;

DROP TABLE t0, t1;

--echo # End of 10.11 tests

@grooverdan grooverdan Aug 16, 2026

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just single line on End of x tests.

Can the tests be appended to mysql-test/main/olap.test instead of a new file.

@jaeheonshim jaeheonshim Aug 17, 2026

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I initially had it that way, but the olap tests don't include innodb and I wasn't sure about including it for the whole file just for these tests

1 change: 1 addition & 0 deletions mysql-test/main/ps_error.result
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ EXECUTE stmt;
ERROR 22007: Truncated incorrect DOUBLE value: 'foo'
SELECT a FROM t1 GROUP BY NULL WITH ROLLUP;
a
NULL
DROP TABLE t1;
SET sql_mode=DEFAULT;
SET SQL_MODE= 'STRICT_ALL_TABLES';
Expand Down
1 change: 1 addition & 0 deletions mysql-test/main/win.result
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Original file line number Diff line number Diff line change
Expand Up @@ -3503,6 +3503,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
select distinct 1, row_number() over (order by 1) from t1 where a=0 group by a with rollup;
1 row_number() over (order by 1)
1 1
drop table t1;
explain
SELECT DISTINCT BIT_OR(100) OVER () FROM dual
Expand Down
1 change: 1 addition & 0 deletions mysql-test/suite/encryption/r/tempfiles_encrypted.result
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Expand Up @@ -3509,6 +3509,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
select distinct 1, row_number() over (order by 1) from t1 where a=0 group by a with rollup;
1 row_number() over (order by 1)
1 1
drop table t1;
explain
SELECT DISTINCT BIT_OR(100) OVER () FROM dual
Expand Down
2 changes: 1 addition & 1 deletion sql/opt_subselect.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -6805,7 +6805,7 @@ bool JOIN::choose_tableless_subquery_plan()
*/
if (zero_result_cause)
{
if (!implicit_grouping)
if (!implicit_grouping && select_lex->olap != ROLLUP_TYPE)
{
/*
Both group by queries and non-group by queries without aggregate
Expand Down
18 changes: 14 additions & 4 deletions sql/sql_select.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -16610,6 +16610,10 @@ return_zero_rows(JOIN *join, select_result *result, List<TABLE_LIST> *tables,
join->thd->set_examined_row_count(0);
join->thd->limit_found_rows= 0;
}
else
{
join->thd->limit_found_rows= send_row ? 1 : 0;
}

if (!(result->send_result_set_metadata(*fields,
Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF)))
Expand Down Expand Up @@ -24496,6 +24500,7 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab, bool end_of_records)
join->fields.
*/
List<Item> *fields= join_tab ? (join_tab-1)->fields : join->fields;
bool empty_set_send_rollup_total= false;
DBUG_ENTER("end_send_group");

if (!join->items3.is_null() && !join->set_group_rpa)
Expand All @@ -24511,7 +24516,8 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab, bool end_of_records)

if (!join->group_sent &&
(join->first_record ||
(end_of_records && !join->group && !join->group_optimized_away)))
join->need_empty_set_row(end_of_records,
&empty_set_send_rollup_total)))
{
table_map cleared_tables= (table_map) 0;
if (join->procedure)
Expand Down Expand Up @@ -24567,7 +24573,8 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab, bool end_of_records)
join->send_records++;
join->group_sent= true;
}
if (unlikely(join->rollup.state != ROLLUP::STATE_NONE && error <= 0))
if (unlikely(join->rollup.state != ROLLUP::STATE_NONE &&
!empty_set_send_rollup_total && error <= 0))
{
if (join->rollup_send_data((uint) (idx+1)))
error= 1;
Expand Down Expand Up @@ -24888,13 +24895,15 @@ end_write_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
{
TABLE *table= join_tab->table;
int idx= -1;
bool empty_set_send_rollup_total= false;
DBUG_ENTER("end_write_group");

join->accepted_rows++;
if (!join->first_record || end_of_records ||
(idx=test_if_group_changed(join->group_fields)) >= 0)
{
if (join->first_record || (end_of_records && !join->group))
if (join->first_record ||
join->need_empty_set_row(end_of_records, &empty_set_send_rollup_total))
{
table_map cleared_tables= (table_map) 0;
if (join->procedure)
Expand All @@ -24919,7 +24928,8 @@ end_write_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
error, 0, NULL))
DBUG_RETURN(NESTED_LOOP_ERROR);
}
if (unlikely(join->rollup.state != ROLLUP::STATE_NONE))
if (unlikely(join->rollup.state != ROLLUP::STATE_NONE &&
!empty_set_send_rollup_total))
{
if (unlikely(join->rollup_write_data((uint) (idx+1),
join_tab->tmp_table_param,
Expand Down
19 changes: 17 additions & 2 deletions sql/sql_select.h
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Expand Up @@ -1746,12 +1746,27 @@ class JOIN :public Sql_alloc
void cleanup(bool full);
void clear(table_map *cleared_tables);
void inline clear_sum_funcs();
bool need_empty_set_row(bool end_of_records,
bool *empty_set_send_rollup_total) const
{
*empty_set_send_rollup_total=
end_of_records && !first_record && rollup.state != ROLLUP::STATE_NONE;
return (end_of_records && !first_record && !group &&
!group_optimized_away) ||

@mariadb-RexJohnston mariadb-RexJohnston Aug 17, 2026

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this is a new condition. Do we need this?

@jaeheonshim jaeheonshim Aug 17, 2026

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It's mainly for code cleanliness. Previously the need_empty_set_row condition was present directly in the if statement in end_send_group/end_write_group. But I figured with the extra condition for empty_set_rollup_total, which needs to be referenced again later, the code would start having many duplicated expressions.

@mariadb-RexJohnston mariadb-RexJohnston Aug 17, 2026

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sorry, i meant group_optimized_away. It's likely not an issue, i was curious.

@jaeheonshim jaeheonshim Aug 17, 2026

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ohh i see. actually I am curious too because group_optimized_away was included in the conditional in end_send_group but not end_write_group. But I believe it should be included in both to be consistent with send_row_on_empty_set

*empty_set_send_rollup_total;
}
bool send_row_on_empty_set()
{
return (do_send_rows && implicit_grouping && !group_optimized_away &&
return (do_send_rows &&
(select_lex->olap == ROLLUP_TYPE ||
(implicit_grouping && !group_optimized_away)) &&
having_value != Item::COND_FALSE);
}
bool empty_result() { return (zero_result_cause && !implicit_grouping); }
bool empty_result()
{
return (zero_result_cause && !implicit_grouping &&
select_lex->olap != ROLLUP_TYPE);
}
bool change_result(select_result *new_result, select_result *old_result);
bool is_top_level_join() const
{
Expand Down