4 files changed, 113 insertions, 0 deletions
diff --git a/mysql-test/r/multi_update_tiny_hash.result b/mysql-test/r/multi_update_tiny_hash.result
new file mode 100644
index 00000000000..d8983123aac
--- /dev/null
+++ b/mysql-test/r/multi_update_tiny_hash.result
@@ -0,0 +1,45 @@
+drop table if exists t1, t2;
+#
+# Bug #36676: multiupdate using LEFT JOIN updates only
+#             first row or fails with an error:
+#  ERROR 1022 (23000): Can't write; duplicate key in table ''
+#
+
+#
+# Multiupdate creates MyISAM temporary table without MEMORY table
+#
+CREATE TABLE t1 (ID INT);
+CREATE TABLE t2 (ID INT,
+s1 TEXT, s2 TEXT, s3 VARCHAR(10), s4 TEXT, s5 VARCHAR(10));
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (1,'test', 'test', 'test', 'test', 'test'),
+(2,'test', 'test', 'test', 'test', 'test');
+SELECT * FROM t1 LEFT JOIN t2 USING(ID);
+ID	s1	s2	s3	s4	s5
+1	test	test	test	test	test
+2	test	test	test	test	test
+UPDATE t1 LEFT JOIN t2 USING(ID) SET s1 = 'changed';
+UPDATE t1 JOIN t2 USING(ID) SET s2 = 'changed';
+UPDATE t1 LEFT JOIN t2 USING(ID) SET s3 = 'changed';
+UPDATE t1 LEFT JOIN t2 USING(ID) SET s4 = 'changed', s5 = 'changed';
+SELECT * FROM t1 LEFT JOIN t2 USING(ID);
+ID	s1	s2	s3	s4	s5
+1	changed	changed	changed	changed	changed
+2	changed	changed	changed	changed	changed
+DROP TABLE t1, t2;
+#
+# Multiupdate creates temporary MyISAM table from MEMORY table
+#
+CREATE TABLE t1 (id INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
+CREATE TABLE t2 (id INT, s1 CHAR(255));
+INSERT INTO t1 VALUES (0), (0), (0), (0), (0), (0), (0), (0);
+INSERT INTO t1 (SELECT 0 FROM t1);
+INSERT INTO t1 (SELECT 0 FROM t1);
+INSERT INTO t1 (SELECT 0 FROM t1);
+INSERT INTO t2 (SELECT ID, 'a' FROM t1);
+UPDATE t1 LEFT JOIN t2 USING(id) SET s1 = 'b';
+SELECT DISTINCT s1 FROM t1 LEFT JOIN t2 USING(id);
+s1
+b
+DROP TABLE t1, t2;
+# End of 5.0 tests
diff --git a/mysql-test/t/multi_update_tiny_hash-master.opt b/mysql-test/t/multi_update_tiny_hash-master.opt
new file mode 100644
index 00000000000..d81cc55090d
--- /dev/null
+++ b/mysql-test/t/multi_update_tiny_hash-master.opt
@@ -0,0 +1 @@
+--set-variable=max_heap_table_size=16384
diff --git a/mysql-test/t/multi_update_tiny_hash.test b/mysql-test/t/multi_update_tiny_hash.test
new file mode 100644
index 00000000000..10d469fb076
--- /dev/null
+++ b/mysql-test/t/multi_update_tiny_hash.test
@@ -0,0 +1,61 @@
+#
+# Test of update statement that uses many tables,
+# --max_heap_table_size=1
+#
+
+--disable_warnings
+drop table if exists t1, t2;
+--enable_warnings
+
+--echo #
+--echo # Bug #36676: multiupdate using LEFT JOIN updates only
+--echo #             first row or fails with an error:
+--echo #  ERROR 1022 (23000): Can't write; duplicate key in table ''
+--echo #
+
+--echo
+
+--echo #
+--echo # Multiupdate creates MyISAM temporary table without MEMORY table
+--echo #
+
+CREATE TABLE t1 (ID INT);
+CREATE TABLE t2 (ID INT,
+  s1 TEXT, s2 TEXT, s3 VARCHAR(10), s4 TEXT, s5 VARCHAR(10));
+
+INSERT INTO t1 VALUES (1),(2);
+INSERT INTO t2 VALUES (1,'test', 'test', 'test', 'test', 'test'),
+                      (2,'test', 'test', 'test', 'test', 'test');
+
+SELECT * FROM t1 LEFT JOIN t2 USING(ID);
+UPDATE t1 LEFT JOIN t2 USING(ID) SET s1 = 'changed';
+UPDATE t1 JOIN t2 USING(ID) SET s2 = 'changed';
+UPDATE t1 LEFT JOIN t2 USING(ID) SET s3 = 'changed';
+UPDATE t1 LEFT JOIN t2 USING(ID) SET s4 = 'changed', s5 = 'changed';
+SELECT * FROM t1 LEFT JOIN t2 USING(ID); 
+
+DROP TABLE t1, t2;
+
+--echo #
+--echo # Multiupdate creates temporary MyISAM table from MEMORY table
+--echo #
+
+CREATE TABLE t1 (id INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
+CREATE TABLE t2 (id INT, s1 CHAR(255));
+
+# insert [1..64] into table `t1`
+INSERT INTO t1 VALUES (0), (0), (0), (0), (0), (0), (0), (0);
+INSERT INTO t1 (SELECT 0 FROM t1);
+INSERT INTO t1 (SELECT 0 FROM t1);
+INSERT INTO t1 (SELECT 0 FROM t1);
+
+INSERT INTO t2 (SELECT ID, 'a' FROM t1);
+
+UPDATE t1 LEFT JOIN t2 USING(id) SET s1 = 'b';
+
+SELECT DISTINCT s1 FROM t1 LEFT JOIN t2 USING(id);
+
+DROP TABLE t1, t2;
+
+
+--echo # End of 5.0 tests
diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index a8238141f25..6830564111b 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -1440,6 +1440,12 @@ bool multi_update::send_data(List<Item> &not_used_values)
           tbl->file->position(tbl->record[0]);
         memcpy((char*) tmp_table->field[field_num]->ptr,
                (char*) tbl->file->ref, tbl->file->ref_length);
+        /*
+         For outer joins a rowid field may have no NOT_NULL_FLAG,
+         so we have to reset NULL bit for this field.
+         (set_notnull() resets NULL bit only if available).
+        */
+        tmp_table->field[field_num]->set_notnull();
         field_num++;
       } while ((tbl= tbl_it++));