Fix LP BUG#613029

Analysis:
There are two code paths through which JOIN::exec may produce
an all-NULL row for an empty result set. One goes via the
function return_zero_rows(), when query processing detectes
early that the where clause is false, the other one is via
do_select() in the case of join execution.

In the case of do_select(), the problem was that the executioner
didn't set TABLE::null_row to 1. As result when sending the only
result row, the evaluation of each field didn't detect that all
non-aggregated fields are NULL, because Field::is_null returned
true, after checking that field->table->null_row was false.

Given that the each non-aggregated field was not considered NULL,
select_result::send_data sent whatever was in the buffer of each
field. However, since there was no actual data in the field buffer,
send_data() accessed and sent whatever junk was in the field's
data buffer.

Solution:
Similar to the analogous case in return_zero_rows() mark all
tables that their current row is NULL before sending the
artificailly created NULL row.

mysql-test/r/subselect4.result

@@ -1133,3 +1133,55 @@ SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM
 f1	f2
 set @@optimizer_switch=@save_optimizer_switch;
 drop table t1,t2;
+#
+# LP BUG#613029 Wrong result with materialization and semijoin, and
+# valgrind warnings in Protocol::net_store_data with materialization
+# for implicit grouping
+#
+CREATE TABLE t1 (
+pk int(11) NOT NULL AUTO_INCREMENT,
+f2 int(11) NOT NULL,
+f3 varchar(1) NOT NULL,
+PRIMARY KEY (pk),
+KEY f2 (f2));
+INSERT INTO t1 VALUES (1,9,'x');
+INSERT INTO t1 VALUES (2,5,'g');
+CREATE TABLE t2 (
+pk int(11) NOT NULL AUTO_INCREMENT,
+f2 int(11) NOT NULL,
+f3 varchar(1) NOT NULL,
+PRIMARY KEY (pk),
+KEY f2 (f2));
+INSERT INTO t2 VALUES (1,7,'p');
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch='materialization=off,semijoin=off';
+EXPLAIN
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+2	DEPENDENT SUBQUERY	t1	index_subquery	f2	f2	4	func	2	Using index
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+f3	MAX(t1.f2)
+NULL	NULL
+set @@optimizer_switch='materialization=on,semijoin=off';
+EXPLAIN
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	system	PRIMARY	NULL	NULL	NULL	1	
+1	PRIMARY	t1	const	PRIMARY	PRIMARY	4	const	1	
+2	SUBQUERY	t1	index	NULL	f2	4	NULL	2	Using index
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+f3	MAX(t1.f2)
+NULL	NULL
+TODO: add a test case for semijoin when the wrong result is fixed
+set @@optimizer_switch='materialization=off,semijoin=on';
+set @@optimizer_switch=@save_optimizer_switch;
+drop table t1, t2;

mysql-test/t/subselect4.test

@@ -906,3 +906,60 @@ SELECT * FROM t1 WHERE (2, 0) NOT IN (SELECT min(f3)+f3, min(f4)+f3+max(f4) FROM
 set @@optimizer_switch=@save_optimizer_switch;
 
 drop table t1,t2;
+
+--echo #
+--echo # LP BUG#613029 Wrong result with materialization and semijoin, and
+--echo # valgrind warnings in Protocol::net_store_data with materialization
+--echo # for implicit grouping
+--echo #
+
+CREATE TABLE t1 (
+  pk int(11) NOT NULL AUTO_INCREMENT,
+  f2 int(11) NOT NULL,
+  f3 varchar(1) NOT NULL,
+  PRIMARY KEY (pk),
+  KEY f2 (f2));
+
+INSERT INTO t1 VALUES (1,9,'x');
+INSERT INTO t1 VALUES (2,5,'g');
+
+CREATE TABLE t2 (
+  pk int(11) NOT NULL AUTO_INCREMENT,
+  f2 int(11) NOT NULL,
+  f3 varchar(1) NOT NULL,
+  PRIMARY KEY (pk),
+  KEY f2 (f2));
+
+INSERT INTO t2 VALUES (1,7,'p');
+
+set @save_optimizer_switch=@@optimizer_switch;
+
+set @@optimizer_switch='materialization=off,semijoin=off';
+
+EXPLAIN
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+
+set @@optimizer_switch='materialization=on,semijoin=off';
+
+EXPLAIN
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+
+SELECT t1.f3, MAX(t1.f2)
+FROM t1, t2
+WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
+
+-- echo TODO: add a test case for semijoin when the wrong result is fixed
+-- echo set @@optimizer_switch='materialization=off,semijoin=on';
+
+
+set @@optimizer_switch=@save_optimizer_switch;
+
+drop table t1, t2;

sql/sql_select.cc

@@ -13452,6 +13452,13 @@ do_select(JOIN *join,List<Item> *fields,TABLE *table,Procedure *procedure)
       {
         List<Item> *columns_list= (procedure ? &join->procedure_fields_list :
                                    fields);
+        /*
+          With implicit grouping all fields of special row produced for an
+          empty result are NULL. See return_zero_rows() for the same behavior.
+        */
+        for (TABLE_LIST *table= join->select_lex->leaf_tables;
+             table; table= table->next_leaf)
+          mark_as_null_row(table->table);
         rc= join->result->send_data(*columns_list);
       }
     }

sql/sql_select.h

@@ -954,8 +954,8 @@ class JOIN :public Sql_alloc
   bool init_save_join_tab();
   bool send_row_on_empty_set()
   {
-    return (do_send_rows && tmp_table_param.sum_func_count != 0 &&
-	    !group_list && having_value != Item::COND_FALSE);
+    return (do_send_rows && implicit_grouping &&
+            having_value != Item::COND_FALSE);
   }
   bool change_result(select_result *result);
   bool is_top_level_join() const