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Fix for #58422: Incorrect result when OUTER JOIN'ing with an empty table.

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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*).
This commit is contained in:
Ole John Aske
2011-01-13 11:42:48 +01:00
parent e17c9279ee
commit 970c3fb244
3 changed files with 136 additions and 2 deletions
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64
mysql-test/r/select.result
View File

@@ -4867,6 +4867,70 @@ SELECT 1 FROM t1 ORDER BY a COLLATE latin1_german2_ci;
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);
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
#
# Bug#54515: Crash in opt_range.cc::get_best_group_min_max on

70
mysql-test/t/select.test
View File

@@ -4123,6 +4123,76 @@ SELECT 1 FROM t1 ORDER BY a COLLATE latin1_german2_ci;
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
--echo #

4
sql/sql_select.cc
View File

@@ -12040,7 +12040,7 @@ join_read_const_table(JOIN_TAB *tab, POSITION *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);
}
}
@@ -12061,7 +12061,7 @@ join_read_const_table(JOIN_TAB *tab, POSITION *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);
}
}