Hi Ole John,
thank you for fixing this bug.
The fix is approved.
Please see one suggestion for simplification of testing.
On 07.12.10 12.50, Ole John Aske wrote:
> #At file:///net/fimafeng09/export/home/tmp/oleja/mysql/mysql-5.1/ based on
> revid:georgi.kodinov@stripped
>
> 3477 Ole John Aske 2010-12-07
> Fix for bug#58422: Incorrect result when OUTER JOIN'ing with an empty table
>
> Fixed incorrect checks in join_read_const_table() for when to
> accept a non-existing, or empty const-row as a part of the const'ified
> set of tables.
>
> Intention of this test is to only accept NULL-rows if this table is outer
> joined
> into the resultset. (In case of an inner-join we can conclude at this point
> that
> resultset will be empty, end we want to return 'error' to signal this.)
>
> Initially 'maybe_null' is set to the same value as 'outer_join' in
> setup_table_map(), mysql_priv.h ~line 2424. Later simplify_joins() will
> attemp to replace outer joins by inner join whenever possible. This
> will cause 'outer_join' to be updated. However, 'maybe_null' is *not* updated
> to reflect this rewrite as this field is used to currectly set the
> 'nullability'
> property for the columns in the resultset.
>
> We should therefore change join_read_const_table() to check the 'outer_join'
> property instead of 'maybe_null', as this correctly reflect the nullability
> of
> the *execution plan* (not *resultset*).
>
> modified:
> mysql-test/r/select.result
> mysql-test/t/select.test
> sql/sql_select.cc
> === modified file 'mysql-test/r/select.result'
> --- a/mysql-test/r/select.result 2010-06-24 08:00:48 +0000
> +++ b/mysql-test/r/select.result 2010-12-07 11:50:00 +0000
> @@ -4797,4 +4797,68 @@ SELECT 1 FROM t1 ORDER BY a COLLATE lati
> 1
> 1
> DROP TABLE t1;
> +#
> +# Bug #58422: Incorrect result when OUTER JOIN'ing
> +# with an empty table
> +#
> +CREATE TABLE t_empty(pk INT PRIMARY KEY, i INT) ENGINE = MYISAM;
> +CREATE TABLE t1(pk INT PRIMARY KEY, i INT) ENGINE = MYISAM;
> +INSERT INTO t1 VALUES (1,1), (2,2), (3,3);
> +CREATE TABLE t2(pk INT PRIMARY KEY, i INT) ENGINE = MYISAM;
> +INSERT INTO t2 VALUES (1,1), (2,2), (3,3);
You may write the below queries as follows for a shorter test specification:
let $query=
SELECT * FROM ...;
eval explain $query;
eval $query;
> +EXPLAIN
> +SELECT *
> +FROM
> +t1
> +LEFT OUTER JOIN
> +(t2 INNER JOIN t_empty ON TRUE)
> +ON t1.pk=t2.pk
> +WHERE t2.pk<> 2;
> +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 *
> +FROM
> +t1
> +LEFT OUTER JOIN
> +(t2 INNER JOIN t_empty ON TRUE)
> +ON t1.pk=t2.pk
> +WHERE t2.pk<> 2;
> +pk i pk i pk i
> +EXPLAIN
> +SELECT *
> +FROM
> +t1
> +LEFT OUTER JOIN
> +(t2 CROSS JOIN t_empty)
> +ON t1.pk=t2.pk
> +WHERE t2.pk<> 2;
> +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 *
> +FROM
> +t1
> +LEFT OUTER JOIN
> +(t2 CROSS JOIN t_empty)
> +ON t1.pk=t2.pk
> +WHERE t2.pk<> 2;
> +pk i pk i pk i
> +EXPLAIN
> +SELECT *
> +FROM
> +t1
> +LEFT OUTER JOIN
> +(t2 INNER JOIN t_empty ON t_empty.i=t2.i)
> +ON t1.pk=t2.pk
> +WHERE t2.pk<> 2;
> +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 *
> +FROM
> +t1
> +LEFT OUTER JOIN
> +(t2 INNER JOIN t_empty ON t_empty.i=t2.i)
> +ON t1.pk=t2.pk
> +WHERE t2.pk<> 2;
> +pk i pk i pk i
> +DROP TABLE t1,t2,t_empty;
> End of 5.1 tests
>
> === modified file 'mysql-test/t/select.test'
> --- a/mysql-test/t/select.test 2010-06-24 17:13:08 +0000
> +++ b/mysql-test/t/select.test 2010-12-07 11:50:00 +0000
> @@ -4088,4 +4088,74 @@ SELECT 1 FROM t1 ORDER BY a COLLATE lati
> DROP TABLE t1;
>
>
> +
> +--echo #
> +--echo # Bug #58422: Incorrect result when OUTER JOIN'ing
> +--echo # with an empty table
> +--echo #
> +
> +CREATE TABLE t_empty(pk INT PRIMARY KEY, i INT) ENGINE = MYISAM;
> +CREATE TABLE t1(pk INT PRIMARY KEY, i INT) ENGINE = MYISAM;
> +INSERT INTO t1 VALUES (1,1), (2,2), (3,3);
> +CREATE TABLE t2(pk INT PRIMARY KEY, i INT) ENGINE = MYISAM;
> +INSERT INTO t2 VALUES (1,1), (2,2), (3,3);
> +
> +EXPLAIN
> +SELECT *
> + FROM
> + t1
> + LEFT OUTER JOIN
> + (t2 INNER JOIN t_empty ON TRUE)
> + ON t1.pk=t2.pk
> + WHERE t2.pk<> 2;
> +
> +SELECT *
> + FROM
> + t1
> + LEFT OUTER JOIN
> + (t2 INNER JOIN t_empty ON TRUE)
> + ON t1.pk=t2.pk
> + WHERE t2.pk<> 2;
> +
> +
> +EXPLAIN
> +SELECT *
> + FROM
> + t1
> + LEFT OUTER JOIN
> + (t2 CROSS JOIN t_empty)
> + ON t1.pk=t2.pk
> + WHERE t2.pk<> 2;
> +
> +SELECT *
> + FROM
> + t1
> + LEFT OUTER JOIN
> + (t2 CROSS JOIN t_empty)
> + ON t1.pk=t2.pk
> + WHERE t2.pk<> 2;
> +
> +
> +EXPLAIN
> +SELECT *
> + FROM
> + t1
> + LEFT OUTER JOIN
> + (t2 INNER JOIN t_empty ON t_empty.i=t2.i)
> + ON t1.pk=t2.pk
> + WHERE t2.pk<> 2;
> +
> +SELECT *
> + FROM
> + t1
> + LEFT OUTER JOIN
> + (t2 INNER JOIN t_empty ON t_empty.i=t2.i)
> + ON t1.pk=t2.pk
> + WHERE t2.pk<> 2;
> +
> +
> +
> +DROP TABLE t1,t2,t_empty;
> +
> +
> --echo End of 5.1 tests
>
> === modified file 'sql/sql_select.cc'
> --- a/sql/sql_select.cc 2010-10-29 08:23:06 +0000
> +++ b/sql/sql_select.cc 2010-12-07 11:50:00 +0000
> @@ -11787,7 +11787,7 @@ join_read_const_table(JOIN_TAB *tab, POS
> /* Mark for EXPLAIN that the row was not found */
> pos->records_read=0.0;
> pos->ref_depend_map= 0;
> - if (!table->maybe_null || error> 0)
> + if (!table->pos_in_table_list->outer_join || error> 0)
> DBUG_RETURN(error);
> }
> }
> @@ -11808,7 +11808,7 @@ join_read_const_table(JOIN_TAB *tab, POS
> /* Mark for EXPLAIN that the row was not found */
> pos->records_read=0.0;
> pos->ref_depend_map= 0;
> - if (!table->maybe_null || error> 0)
> + if (!table->pos_in_table_list->outer_join || error> 0)
> DBUG_RETURN(error);
> }
> }
Thanks,
Roy
