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MDEV-32868 SELECT NULL,NULL IN (SUBQUERY) returns 0 instead of NULL #4550

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MDEV-32868 SELECT NULL,NULL IN (SUBQUERY) returns 0 instead of NULL #4550

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MDEV-32868 SELECT NULL,NULL IN (SUBQUERY) returns 0 instead of NULL
Olernov Jan 16, 2026
3811b51
MDEV-32868 Cleanup (no change of logic)
Olernov Jan 27, 2026
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47 changes: 47 additions & 0 deletions mysql-test/main/subselect_nulls.result
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Original file line number Diff line number Diff line change
Expand Up @@ -154,3 +154,50 @@ drop table t1, t2;
#
# End of 10.10 tests
#
#
# MDEV-32868 SELECT NULL,NULL IN (SUBQUERY) returns 0 instead of NULL
#
create table t1 (a int);
insert into t1 values (1);
create table t2 (a int, b int);
insert into t2 values (null, null);
# Scalar subquery returning NULLs as left part of IN
# All NULLs on left, no match possible -> NULL (subquery has rows)
select (select null, null) in (select 1, 2 from t1) from t1;
(select null, null) in (select 1, 2 from t1)
NULL
# One NULL on left, other column matches -> NULL
select (select null, 2) in (select 1, 2 from t1) from t1;
(select null, 2) in (select 1, 2 from t1)
NULL
# One NULL on left, other column doesn't match -> FALSE
select (select null, 3) in (select 1, 2 from t1) from t1;
(select null, 3) in (select 1, 2 from t1)
0
# Table with NULLs as left part
select (select * from t2) in (select 1, 2 from t1) from t1;
(select * from t2) in (select 1, 2 from t1)
NULL
# Exact match -> TRUE
select (select 1, 2) in (select 1, 2 from t1) from t1;
(select 1, 2) in (select 1, 2 from t1)
1
# No match, no NULLs -> FALSE
select (select 3, 4) in (select 1, 2 from t1) from t1;
(select 3, 4) in (select 1, 2 from t1)
0
# Right side has NULLs
create table t3 (a int, b int);
insert into t3 values (1, null), (null, 2);
# Left matches one column, right has NULL in other -> NULL
select (select 1, 2) in (select * from t3) from t1;
(select 1, 2) in (select * from t3)
NULL
# Both sides have NULLs -> NULL
select (select null, 2) in (select * from t3) from t1;
(select null, 2) in (select * from t3)
NULL
drop table t1, t2, t3;
#
# End of 10.11 tests
#
45 changes: 45 additions & 0 deletions mysql-test/main/subselect_nulls.test
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Expand Up @@ -127,3 +127,48 @@ drop table t1, t2;
--echo #
--echo # End of 10.10 tests
--echo #

--echo #
--echo # MDEV-32868 SELECT NULL,NULL IN (SUBQUERY) returns 0 instead of NULL
--echo #

create table t1 (a int);
insert into t1 values (1);

create table t2 (a int, b int);
insert into t2 values (null, null);

--echo # Scalar subquery returning NULLs as left part of IN
--echo # All NULLs on left, no match possible -> NULL (subquery has rows)
select (select null, null) in (select 1, 2 from t1) from t1;

--echo # One NULL on left, other column matches -> NULL
select (select null, 2) in (select 1, 2 from t1) from t1;

--echo # One NULL on left, other column doesn't match -> FALSE
select (select null, 3) in (select 1, 2 from t1) from t1;

--echo # Table with NULLs as left part
select (select * from t2) in (select 1, 2 from t1) from t1;

--echo # Exact match -> TRUE
select (select 1, 2) in (select 1, 2 from t1) from t1;

--echo # No match, no NULLs -> FALSE
select (select 3, 4) in (select 1, 2 from t1) from t1;

--echo # Right side has NULLs
create table t3 (a int, b int);
insert into t3 values (1, null), (null, 2);

--echo # Left matches one column, right has NULL in other -> NULL
select (select 1, 2) in (select * from t3) from t1;

--echo # Both sides have NULLs -> NULL
select (select null, 2) in (select * from t3) from t1;

drop table t1, t2, t3;

--echo #
--echo # End of 10.11 tests
--echo #
12 changes: 6 additions & 6 deletions sql/sql_select.cc
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Expand Up @@ -13307,12 +13307,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
{
Json_writer_object trace_const_cond(thd);
trace_const_cond.add("condition_on_constant_tables", const_cond);
if (const_cond->is_expensive())
{
trace_const_cond.add("evaluated", "false")
.add("cause", "expensive cond");
}
else
if (const_cond->can_eval_in_optimize())
{
bool const_cond_result;
{
Expand All @@ -13328,6 +13323,11 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
DBUG_RETURN(1);
}
}
else
{
trace_const_cond.add("evaluated", "false")
.add("cause", "expensive cond");
}
join->exec_const_cond= const_cond;
}

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