From 970c3fb244d07e019fb86dc660fcdd94e2174c82 Mon Sep 17 00:00:00 2001 From: Ole John Aske Date: Thu, 13 Jan 2011 11:42:48 +0100 Subject: [PATCH] Fix for #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*). --- mysql-test/r/select.result | 64 ++++++++++++++++++++++++++++++++++ mysql-test/t/select.test | 70 ++++++++++++++++++++++++++++++++++++++ sql/sql_select.cc | 4 +-- 3 files changed, 136 insertions(+), 2 deletions(-) diff --git a/mysql-test/r/select.result b/mysql-test/r/select.result index a345a2ae6aa..af0ef29bb53 100644 --- a/mysql-test/r/select.result +++ b/mysql-test/r/select.result @@ -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 diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test index 3ed7213e8d7..043b03e4686 100644 --- a/mysql-test/t/select.test +++ b/mysql-test/t/select.test @@ -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 # diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 26216225c3f..fdce2510df4 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -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); } }