unpack_row: set the correct fields in has_value_set for online alter

mysql-test/main/alter_table_online_debug.result

@@ -1312,6 +1312,40 @@ insert into t select repeat('a',130000);
 set debug_sync= "now signal end";
 connection default;
 drop table t;
+#
+# Test that correct fields are marked as explicit:
+# Drop a, reorder b, add new column with default.
+#
+create table t (a int primary key, b int) engine=innodb;
+insert into t values (1, 1), (2, 2), (3, 3);
+set debug_sync= "alter_table_copy_end signal copy wait_for goon";
+alter table t drop primary key, drop a,
+change b c bigint,
+add x longblob default 123456;
+connection con1;
+set debug_sync= "now wait_for copy";
+update t set b = 5 where a = 1;
+update t set b = NULL where a = 1;
+select * from t;
+a	b
+1	NULL
+2	2
+3	3
+update t set a = 100 where a = 1;
+update t set b = -10 where a = 100;
+select * from t;
+a	b
+2	2
+3	3
+100	-10
+set debug_sync= "now signal goon";
+connection default;
+select * from t;
+c	x
+-10	123456
+2	123456
+3	123456
+drop table t;
 set debug_sync= reset;
 disconnect con1;
 disconnect con2;

mysql-test/main/alter_table_online_debug.test

@@ -1498,6 +1498,35 @@ set debug_sync= "now signal end";
 --reap
 drop table t;
 
+--echo #
+--echo # Test that correct fields are marked as explicit:
+--echo # Drop a, reorder b, add new column with default.
+--echo #
+create table t (a int primary key, b int) engine=innodb;
+insert into t values (1, 1), (2, 2), (3, 3);
+
+set debug_sync= "alter_table_copy_end signal copy wait_for goon";
+send alter table t drop primary key, drop a,
+                   change b c bigint,
+                   add x longblob default 123456;
+
+--connection con1
+set debug_sync= "now wait_for copy";
+
+update t set b = 5 where a = 1;
+update t set b = NULL where a = 1;
+select * from t;
+update t set a = 100 where a = 1;
+update t set b = -10 where a = 100;
+select * from t;
+
+set debug_sync= "now signal goon";
+
+--connection default
+--reap
+select * from t;
+drop table t;
+
 
 set debug_sync= reset;
 --disconnect con1

sql/rpl_record.cc

@@ -254,7 +254,8 @@ int unpack_row(const rpl_group_info *rgi, TABLE *table, uint const colcnt,
      */
     if (bitmap_is_set(cols, (uint)(field_ptr -  begin_ptr)))
     {
-      (*field_ptr)->set_has_explicit_value();
+      if (!rpl_data.is_online_alter())
+        (*field_ptr)->set_has_explicit_value();
       if ((null_mask & 0xFF) == 0)
       {
         DBUG_ASSERT(null_ptr < row_data + master_null_byte_count);
@@ -376,6 +377,7 @@ int unpack_row(const rpl_group_info *rgi, TABLE *table, uint const colcnt,
     for (const auto *copy=rpl_data.copy_fields;
          copy != rpl_data.copy_fields_end; copy++)
     {
+      copy->to_field->set_has_explicit_value();
       copy->do_copy(copy);
     }
   }