Fix for BUG#49481 and BUG#49482 reverted.

PB2 run uncovered issue that needs further analysis.

mysql-test/suite/rpl/r/rpl_myisam_null_values.result

-stop slave;
-drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
-reset master;
-reset slave;
-drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
-start slave;
-CREATE TABLE t1 (c1 BIT, c2 INT);
-INSERT INTO `t1` VALUES ( 1, 1 );
-UPDATE t1 SET c1=NULL where c2=1;
-Comparing tables master:test.t1 and slave:test.t1
-DELETE FROM t1 WHERE c2=1 LIMIT 1;
-Comparing tables master:test.t1 and slave:test.t1
-DROP TABLE t1;
-CREATE TABLE t1 (c1 CHAR);
-INSERT INTO t1 ( c1 ) VALUES ( 'w' ) ;
-SELECT * FROM t1;
-c1
-w
-# should trigger switch to row due to LIMIT
-UPDATE t1 SET c1=NULL WHERE c1='w' LIMIT 2;
-Comparing tables master:test.t1 and slave:test.t1
-DELETE FROM t1 LIMIT 2;
-Comparing tables master:test.t1 and slave:test.t1
-DROP TABLE t1;

mysql-test/suite/rpl/t/rpl_myisam_null_values.test

-# BUG#49481: RBR: MyISAM and bit fields may cause slave to stop on delete cant find record
-# BUG#49482: RBR: Replication may break on deletes when MyISAM tables + char field are used
-
--- source include/master-slave.inc
--- source include/have_binlog_format_mixed_or_row.inc
-
--- connection master
-CREATE TABLE t1 (c1 BIT, c2 INT);
-INSERT INTO `t1` VALUES ( 1, 1 );
-UPDATE t1 SET c1=NULL where c2=1;
--- sync_slave_with_master
-
--- let $diff_table_1=master:test.t1
--- let $diff_table_2=slave:test.t1
--- source include/diff_tables.inc
-
--- connection master
-DELETE FROM t1 WHERE c2=1 LIMIT 1;
--- sync_slave_with_master
-
--- let $diff_table_1=master:test.t1
--- let $diff_table_2=slave:test.t1
--- source include/diff_tables.inc
-
--- connection master
-DROP TABLE t1;
--- sync_slave_with_master
-
--- connection master
-
-CREATE TABLE t1 (c1 CHAR);
-
-INSERT INTO t1 ( c1 ) VALUES ( 'w' ) ;
-SELECT * FROM t1;
--- echo # should trigger switch to row due to LIMIT
-UPDATE t1 SET c1=NULL WHERE c1='w' LIMIT 2;
--- sync_slave_with_master
-
--- let $diff_table_1=master:test.t1
--- let $diff_table_2=slave:test.t1
--- source include/diff_tables.inc
-
--- connection master
-DELETE FROM t1 LIMIT 2;
--- sync_slave_with_master
-
--- let $diff_table_1=master:test.t1
--- let $diff_table_2=slave:test.t1
--- source include/diff_tables.inc
-
--- connection master
-DROP TABLE t1;
--- sync_slave_with_master

sql/log_event.cc

@@ -8724,24 +8724,6 @@ static bool record_compare(TABLE *table)
     }
   }
 
-  /**
-    Check if we are using MyISAM.
-
-    If this is a myisam table, then we cannot do a memcmp
-    right away because some NULL fields can still contain 
-    an old value in the row - they are not shown to the user
-    because the null bit is set, however, the contents are
-    not cleared. As such, plain memory comparison cannot be 
-    assured to work. See: BUG#49482 and BUG#49481.
-
-    On top of this, we do not store field contents for null 
-    fields in the binlog, so this is extra important when
-    comparing records fetched from binlog and from storage
-    engine.
-  */
-  if (table->file->ht->db_type == DB_TYPE_MYISAM)
-    goto record_compare_field_by_field;
-
   if (table->s->blob_fields + table->s->varchar_fields == 0)
   {
     result= cmp_record(table,record[1]);
@@ -8757,33 +8739,14 @@ static bool record_compare(TABLE *table)
     goto record_compare_exit;
   }
 
-record_compare_field_by_field:
-
   /* Compare updated fields */
   for (Field **ptr=table->field ; *ptr ; ptr++)
   {
-    Field *f= *ptr;
-
-    /* if just one of the fields is null then there is no match */
-    if ((f->is_null_in_record(table->record[0])) ==
-         !(f->is_null_in_record(table->record[1])))
+    if ((*ptr)->cmp_binary_offset(table->s->rec_buff_length))
     {
       result= TRUE;
       goto record_compare_exit;
     }
-
-    /* if both fields are not null then we can compare */
-    if (!(f->is_null_in_record(table->record[0])) &&
-        !(f->is_null_in_record(table->record[1])))
-    {
-      if (f->cmp_binary_offset(table->s->rec_buff_length))
-      {
-        result= TRUE;
-        goto record_compare_exit;
-      }
-    }
-
-    /* if both fields are null then there is a match. compare next field */
   }
 
 record_compare_exit:

sql/log_event_old.cc

@@ -351,24 +351,6 @@ static bool record_compare(TABLE *table)
     }
   }
 
-  /**  
-    Check if we are using MyISAM.
-
-    If this is a myisam table, then we cannot do a memcmp
-    right away because some NULL fields can still contain 
-    an old value in the row - they are not shown to the user
-    because the null bit is set, however, the contents are
-    not cleared. As such, plain memory comparison cannot be 
-    assured to work. See: BUG#49482 and BUG#49481.
-
-    On top of this, we do not store field contents for null 
-    fields in the binlog, so this is extra important when
-    comparing records fetched from binlog and from storage
-    engine.
-  */
-  if (table->file->ht->db_type == DB_TYPE_MYISAM)
-    goto record_compare_field_by_field;
-
   if (table->s->blob_fields + table->s->varchar_fields == 0)
   {
     result= cmp_record(table,record[1]);
@@ -384,35 +366,16 @@ static bool record_compare(TABLE *table)
     goto record_compare_exit;
   }
 
-record_compare_field_by_field:
-
   /* Compare updated fields */
   for (Field **ptr=table->field ; *ptr ; ptr++)
   {
-    Field *f= *ptr;
-
-    /* if just one of the fields is null then there is no match */
-    if ((f->is_null_in_record(table->record[0])) ==
-         !(f->is_null_in_record(table->record[1])))
-    {
-      result= TRUE;
-      goto record_compare_exit;
-    }
-
-    /* if both fields are not null then we can compare */
-    if (!(f->is_null_in_record(table->record[0])) &&
-        !(f->is_null_in_record(table->record[1])))
-    {
-      if (f->cmp_binary_offset(table->s->rec_buff_length))
+    if ((*ptr)->cmp_binary_offset(table->s->rec_buff_length))
     {
       result= TRUE;
       goto record_compare_exit;
     }
   }
 
-    /* if both fields are null then there is a match. compare next field */
-  }
-
 record_compare_exit:
   /*
     Restore the saved bytes.