Bug #44139: Table scan when NULL appears in IN clause

SELECT ... WHERE ... IN (NULL, ...) does full table scan,
even if the same query without the NULL uses efficient range scan.

The bugfix for the bug 18360 introduced an optimization:
if
  1) all right-hand arguments of the IN function are constants
  2) result types of all right argument items are compatible
     enough to use the same single comparison function to
     compare all of them to the left argument,

then

  we can convert the right-hand list of constant items to an array
  of equally-typed constant values for the further
  QUICK index access etc. (see Item_func_in::fix_length_and_dec()).

The Item_null constant item objects have STRING_RESULT
result types, so, as far as Item_func_in::fix_length_and_dec()
is aware of NULLs in the right list, this improvement efficiently
optimizes IN function calls with a mixed right list of NULLs and
string constants. However, the optimization doesn't affect mixed
lists of NULLs and integers, floats etc., because there is no
unique common comparator.


New optimization has been added to ignore the result type
of NULL constants in the static analysis of mixed right-hand lists.
This is safe, because at the execution phase we care about
presence of NULLs anyway.

1. The collect_cmp_types() function has been modified to optionally
   ignore NULL constants in the item list.
2. NULL-skipping code of the Item_func_in::fix_length_and_dec()
   function has been modified to work not only with in_string
   vectors but with in_vectors of other types.


mysql-test/r/func_in.result:
  Added test case for the bug #44139.
mysql-test/t/func_in.test:
  Added test case for the bug #44139.
sql/item_cmpfunc.cc:
  Bug #44139: Table scan when NULL appears in IN clause
  
  1. The collect_cmp_types() function has been modified to optionally
     ignore NULL constants in the item list.
  2. NULL-skipping code of the Item_func_in::fix_length_and_dec()
     function has been modified to work not only with in_string
     vectors but with in_vectors of other types.

mysql-test/r/func_in.result

@@ -608,4 +608,146 @@ SELECT SUM( DISTINCT e ) FROM t1 GROUP BY b,c,d HAVING (b,c,d) IN
 ((AVG( 1 ), 1 + c, 1 + d), (AVG( 1 ), 2 + c, 2 + d));
 SUM( DISTINCT e )
 DROP TABLE t1;
+#
+# Bug #44139: Table scan when NULL appears in IN clause
+#
+CREATE TABLE t1 (
+c_int INT NOT NULL,
+c_decimal DECIMAL(5,2) NOT NULL,
+c_float FLOAT(5, 2) NOT NULL,
+c_bit BIT(10) NOT NULL,
+c_date DATE NOT NULL, 
+c_datetime DATETIME NOT NULL,
+c_timestamp TIMESTAMP NOT NULL,
+c_time TIME NOT NULL,
+c_year YEAR NOT NULL,
+c_char CHAR(10) NOT NULL,
+INDEX(c_int), INDEX(c_decimal), INDEX(c_float), INDEX(c_bit), INDEX(c_date),
+INDEX(c_datetime), INDEX(c_timestamp), INDEX(c_time), INDEX(c_year),
+INDEX(c_char));
+INSERT INTO t1 (c_int) VALUES (1), (2), (3), (4), (5);
+INSERT INTO t1 (c_int) SELECT 0 FROM t1;
+INSERT INTO t1 (c_int) SELECT 0 FROM t1;
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_int	c_int	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL, 1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_int	c_int	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_int	c_int	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (1, NULL, 2, NULL, 3, NULL);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_int	c_int	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_decimal	c_decimal	3	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL, 1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_decimal	c_decimal	3	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_float	c_float	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL, 1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_float	c_float	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_bit	c_bit	2	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL, 1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_bit	c_bit	2	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_date 
+IN ('2009-09-01', '2009-09-02', '2009-09-03');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_date	c_date	3	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_date
+IN (NULL, '2009-09-01', '2009-09-02', '2009-09-03');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_date	c_date	3	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_date IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_date IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_datetime
+IN ('2009-09-01 00:00:01', '2009-09-02 00:00:01', '2009-09-03 00:00:01');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_datetime	c_datetime	8	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_datetime
+IN (NULL, '2009-09-01 00:00:01', '2009-09-02 00:00:01', '2009-09-03 00:00:01');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_datetime	c_datetime	8	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_datetime IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_datetime IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp
+IN ('2009-09-01 00:00:01', '2009-09-01 00:00:02', '2009-09-01 00:00:03');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_timestamp	c_timestamp	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp
+IN (NULL, '2009-09-01 00:00:01', '2009-09-01 00:00:02', '2009-09-01 00:00:03');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_timestamp	c_timestamp	4	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_year	c_year	1	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL, 1, 2, 3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_year	c_year	1	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL, NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_char IN ('1', '2', '3');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_char	c_char	10	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL, '1', '2', '3');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	c_char	c_char	10	NULL	3	Using where
+EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL);
+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
+EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL, NULL);
+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
+DROP TABLE t1;
+#
 End of 5.1 tests

mysql-test/t/func_in.test

@@ -456,4 +456,89 @@ SELECT SUM( DISTINCT e ) FROM t1 GROUP BY b,c,d HAVING (b,c,d) IN
   ((AVG( 1 ), 1 + c, 1 + d), (AVG( 1 ), 2 + c, 2 + d));
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #44139: Table scan when NULL appears in IN clause
+--echo #
+
+--disable_warnings
+
+CREATE TABLE t1 (
+  c_int INT NOT NULL,
+  c_decimal DECIMAL(5,2) NOT NULL,
+  c_float FLOAT(5, 2) NOT NULL,
+  c_bit BIT(10) NOT NULL,
+  c_date DATE NOT NULL, 
+  c_datetime DATETIME NOT NULL,
+  c_timestamp TIMESTAMP NOT NULL,
+  c_time TIME NOT NULL,
+  c_year YEAR NOT NULL,
+  c_char CHAR(10) NOT NULL,
+  INDEX(c_int), INDEX(c_decimal), INDEX(c_float), INDEX(c_bit), INDEX(c_date),
+  INDEX(c_datetime), INDEX(c_timestamp), INDEX(c_time), INDEX(c_year),
+  INDEX(c_char));
+
+INSERT INTO t1 (c_int) VALUES (1), (2), (3), (4), (5);
+INSERT INTO t1 (c_int) SELECT 0 FROM t1;
+INSERT INTO t1 (c_int) SELECT 0 FROM t1;
+
+--enable_warnings
+
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL, 1, 2, 3);
+
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (1, NULL, 2, NULL, 3, NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_int IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL, 1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_decimal IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL, 1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_float IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL, 1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_bit IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_date 
+  IN ('2009-09-01', '2009-09-02', '2009-09-03');
+EXPLAIN SELECT * FROM t1 WHERE c_date
+  IN (NULL, '2009-09-01', '2009-09-02', '2009-09-03');
+EXPLAIN SELECT * FROM t1 WHERE c_date IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_date IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_datetime
+  IN ('2009-09-01 00:00:01', '2009-09-02 00:00:01', '2009-09-03 00:00:01');
+EXPLAIN SELECT * FROM t1 WHERE c_datetime
+  IN (NULL, '2009-09-01 00:00:01', '2009-09-02 00:00:01', '2009-09-03 00:00:01');
+EXPLAIN SELECT * FROM t1 WHERE c_datetime IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_datetime IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp
+  IN ('2009-09-01 00:00:01', '2009-09-01 00:00:02', '2009-09-01 00:00:03');
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp
+  IN (NULL, '2009-09-01 00:00:01', '2009-09-01 00:00:02', '2009-09-01 00:00:03');
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_timestamp IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL, 1, 2, 3);
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_year IN (NULL, NULL);
+
+EXPLAIN SELECT * FROM t1 WHERE c_char IN ('1', '2', '3');
+EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL, '1', '2', '3');
+EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL);
+EXPLAIN SELECT * FROM t1 WHERE c_char IN (NULL, NULL);
+
+DROP TABLE t1;
+
+--echo #
+
 --echo End of 5.1 tests

sql/item_cmpfunc.cc

@@ -189,6 +189,7 @@ enum_field_types agg_field_type(Item **items, uint nitems)
     collect_cmp_types()
       items             Array of items to collect types from
       nitems            Number of items in the array
+      skip_nulls        Don't collect types of NULL items if TRUE
 
   DESCRIPTION
     This function collects different result types for comparison of the first
@@ -199,7 +200,7 @@ enum_field_types agg_field_type(Item **items, uint nitems)
     Bitmap of collected types - otherwise
 */
 
-static uint collect_cmp_types(Item **items, uint nitems)
+static uint collect_cmp_types(Item **items, uint nitems, bool skip_nulls= FALSE)
 {
   uint i;
   uint found_types;
@@ -208,6 +209,8 @@ static uint collect_cmp_types(Item **items, uint nitems)
   found_types= 0;
   for (i= 1; i < nitems ; i++)
   {
+    if (skip_nulls && items[i]->type() == Item::NULL_ITEM)
+      continue; // Skip NULL constant items
     if ((left_result == ROW_RESULT || 
          items[i]->result_type() == ROW_RESULT) &&
         cmp_row_type(items[0], items[i]))
@@ -215,6 +218,12 @@ static uint collect_cmp_types(Item **items, uint nitems)
     found_types|= 1<< (uint)item_cmp_type(left_result,
                                            items[i]->result_type());
   }
+  /*
+   Even if all right-hand items are NULLs and we are skipping them all, we need
+   at least one type bit in the found_type bitmask.
+  */
+  if (skip_nulls && !found_types)
+    found_types= 1 << (uint)left_result;
   return found_types;
 }
 
@@ -3515,7 +3524,7 @@ void Item_func_in::fix_length_and_dec()
   uint type_cnt= 0, i;
   Item_result cmp_type= STRING_RESULT;
   left_result_type= args[0]->result_type();
-  if (!(found_types= collect_cmp_types(args, arg_count)))
+  if (!(found_types= collect_cmp_types(args, arg_count, true)))
     return;
   
   for (arg= args + 1, arg_end= args + arg_count; arg != arg_end ; arg++)
@@ -3693,9 +3702,11 @@ void Item_func_in::fix_length_and_dec()
       uint j=0;
       for (uint i=1 ; i < arg_count ; i++)
       {
-	array->set(j,args[i]);
 	if (!args[i]->null_value)			// Skip NULL values
+        {
+          array->set(j,args[i]);
 	  j++;
+        }
 	else
 	  have_null= 1;
       }