MDEV-30333 Wrong result with not_null_range_scan and LEFT JOIN with e…

…mpty table

There was a bug in JOIN::make_notnull_conds_for_range_scans() when
clearing TABLE->tmp_set, which was used to mark fields that could not be
null.

This function was only used if 'not_null_range_scan=on' is set.

The effect was that tmp_set contained a 'random value' and this caused
the optimizer to think that some fields could not be null.
FLUSH TABLES clears tmp_set and because of this things worked temporarily.

Fixed by clearing tmp_set properly.

mysql-test/main/empty_table.result

@@ -16,3 +16,61 @@ ERROR 42S02: Table 'test.t2' doesn't exist
 show status like "Empty_queries";
 Variable_name	Value
 Empty_queries	2
+# End of 4.1 tests
+#
+# MDEV-30333 Wrong result with not_null_range_scan and LEFT JOIN with empty table
+#
+set @save_optimizer_switch=@@optimizer_switch;
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 (b) VALUES (1),(2);
+CREATE TABLE t2 (c INT) ENGINE=MyISAM;
+SET optimizer_switch= 'not_null_range_scan=off';
+explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t2	system	NULL	NULL	NULL	NULL	0	0.00	Const row not found
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Using filesort
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` is null order by `test`.`t1`.`b`
+SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+b
+1
+2
+SET optimizer_switch = 'not_null_range_scan=on';
+explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t2	system	NULL	NULL	NULL	NULL	0	0.00	Const row not found
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Using filesort
+Warnings:
+Note	1003	select `test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` is null order by `test`.`t1`.`b`
+SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+b
+1
+2
+flush tables;
+SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+b
+1
+2
+drop table t1,t2;
+# Second test in MDEV-30333
+CREATE TABLE t1 (a int, b varchar(10)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (69,'foo'),(71,'bar');
+CREATE TABLE t2 (c int) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+CREATE TABLE t3 (d int, e int, KEY(e)) ENGINE=MyISAM;
+SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
+a	b	c	d	e
+69	foo	1	NULL	NULL
+71	bar	1	NULL	NULL
+69	foo	2	NULL	NULL
+71	bar	2	NULL	NULL
+SET optimizer_switch = 'not_null_range_scan=on';
+SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
+a	b	c	d	e
+69	foo	1	NULL	NULL
+71	bar	1	NULL	NULL
+69	foo	2	NULL	NULL
+71	bar	2	NULL	NULL
+DROP TABLE t1, t2, t3;
+set @@optimizer_switch=@save_optimizer_switch;
+End of 10.5 tests

mysql-test/main/empty_table.test

@@ -21,4 +21,38 @@ drop table t1;
 select * from t2;
 show status like "Empty_queries";
 
-# End of 4.1 tests
+--echo # End of 4.1 tests
+
+--echo #
+--echo # MDEV-30333 Wrong result with not_null_range_scan and LEFT JOIN with empty table
+--echo #
+
+set @save_optimizer_switch=@@optimizer_switch;
+CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
+INSERT INTO t1 (b) VALUES (1),(2);
+CREATE TABLE t2 (c INT) ENGINE=MyISAM;
+SET optimizer_switch= 'not_null_range_scan=off'; # Default
+explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+SET optimizer_switch = 'not_null_range_scan=on';
+explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+flush tables;
+SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
+drop table t1,t2;
+
+--echo # Second test in MDEV-30333
+
+CREATE TABLE t1 (a int, b varchar(10)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (69,'foo'),(71,'bar');
+CREATE TABLE t2 (c int) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(2);
+CREATE TABLE t3 (d int, e int, KEY(e)) ENGINE=MyISAM;
+SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
+SET optimizer_switch = 'not_null_range_scan=on';
+SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
+DROP TABLE t1, t2, t3;
+set @@optimizer_switch=@save_optimizer_switch;
+
+--echo End of 10.5 tests
+

sql/sql_select.cc

@@ -29683,7 +29683,6 @@ void JOIN::make_notnull_conds_for_range_scans()
 {
   DBUG_ENTER("JOIN::make_notnull_conds_for_range_scans");
 
-
   if (impossible_where ||
       !optimizer_flag(thd, OPTIMIZER_SWITCH_NOT_NULL_RANGE_SCAN))
   {
@@ -29769,21 +29768,20 @@ bool build_notnull_conds_for_range_scans(JOIN *join, Item *cond,
                                          table_map allowed)
 {
   THD *thd= join->thd;
-
   DBUG_ENTER("build_notnull_conds_for_range_scans");
 
   for (JOIN_TAB *s= join->join_tab;
        s < join->join_tab + join->table_count ; s++)
   {
     /* Clear all needed bitmaps to mark found fields */
     if ((allowed & s->table->map) &&
-        !(s->table->map && join->const_table_map))
+        !(s->table->map & join->const_table_map))
       bitmap_clear_all(&s->table->tmp_set);
   }
 
   /*
     Find all null-rejected fields assuming that cond is null-rejected and
-    only  formulas over tables from 'allowed' are to be taken into account
+    only formulas over tables from 'allowed' are to be taken into account
   */
   if (cond->find_not_null_fields(allowed))
     DBUG_RETURN(true);