Cleanup unused READ_RECORD::index

sql/records.h

@@ -58,7 +58,6 @@ struct READ_RECORD
   SQL_SELECT *select;
   uint cache_records;
   uint ref_length,struct_length,reclength,rec_cache_size,error_offset;
-  uint index;
   uchar *ref_pos;				/* pointer to form->refpos */
   uchar *record;
   uchar *rec_buf;                /* to read field values  after filesort */

sql/sql_select.cc

@@ -20392,7 +20392,6 @@ join_read_first(JOIN_TAB *tab)
   tab->table->status=0;
   tab->read_record.read_record_func= join_read_next;
   tab->read_record.table=table;
-  tab->read_record.index=tab->index;
   tab->read_record.record=table->record[0];
   if (!table->file->inited)
     error= table->file->ha_index_init(tab->index, tab->sorted);
@@ -20433,7 +20432,6 @@ join_read_last(JOIN_TAB *tab)
   tab->table->status=0;
   tab->read_record.read_record_func= join_read_prev;
   tab->read_record.table=table;
-  tab->read_record.index=tab->index;
   tab->read_record.record=table->record[0];
   if (!table->file->inited)
     error= table->file->ha_index_init(tab->index, 1);