[bugfix] Issue: #64 replication regression with RBR and partition tables

This patch is ported from MySQL upstream (commit id: 9414c7).

Bug#25687813 REPLICATION REGRESSION WITH RBR AND PARTITIONED TABLES

PROBLEM
-------

While applying update the slave is trying to initialize all partitions
before reading from rnd_pos() call. This is done for each row update
because of which the performance is getting effected.

FIX
---

Initialize only the partition on which rnd_pos() is called.

sql/ha_partition.cc

@@ -4981,14 +4981,11 @@ int ha_partition::rnd_pos(uchar * buf, uchar *pos)
 int ha_partition::rnd_pos_by_record(uchar *record)
 {
   DBUG_ENTER("ha_partition::rnd_pos_by_record");
-
   if (unlikely(get_part_for_delete(record, m_rec0, m_part_info, &m_last_part)))
     DBUG_RETURN(1);
-
-  DBUG_RETURN(handler::rnd_pos_by_record(record));
+  DBUG_RETURN(m_file[m_last_part]->rnd_pos_by_record(record));
 }
 
-
 /****************************************************************************
                 MODULE index scan
 ****************************************************************************/

sql/handler.h

@@ -2457,10 +2457,19 @@ class handler :public Sql_alloc
   */
   virtual int rnd_pos_by_record(uchar *record)
     {
+      int error;
       DBUG_ASSERT(table_flags() & HA_PRIMARY_KEY_REQUIRED_FOR_POSITION);
+
+      error = ha_rnd_init(false);
+      if (error != 0)
+          return error;
+
       position(record);
-      return ha_rnd_pos(record, ref);
+      error = ha_rnd_pos(record, ref);
+      ha_rnd_end();
+      return error;
     }
+
   virtual int read_first_row(uchar *buf, uint primary_key);
   /**
     The following function is only needed for tables that may be temporary

sql/log_event.cc

@@ -10655,12 +10655,7 @@ int Rows_log_event::do_index_scan_and_update(Relay_log_info const *rli)
     if (m_table->file->inited && (error= m_table->file->ha_index_end()))
       goto end;
 
-    if ((error= m_table->file->ha_rnd_init(FALSE)))
-      goto end;
-
     error= m_table->file->rnd_pos_by_record(m_table->record[0]);
-
-    m_table->file->ha_rnd_end();
     if (error)
     {
       DBUG_PRINT("info",("rnd_pos returns error %d",error));