Re-run fix-fields on condition if table was reopened in HANDLERREAD

sql/sql_base.cc:
  Added more comments
sql/sql_handler.cc:
  Re-run fix-fields on condition if table was reopened

sql/sql_base.cc

@@ -1012,10 +1012,20 @@ TABLE *find_locked_table(THD *thd, const char *db,const char *table_name)
 
 
 /****************************************************************************
-** Reopen an table because the definition has changed. The date file for the
-** table is already closed.
-** Returns 0 if ok.
-** If table can't be reopened, the entry is unchanged.
+  Reopen an table because the definition has changed. The date file for the
+  table is already closed.
+
+  SYNOPSIS
+    reopen_table()
+    table		Table to be opened
+    locked		1 if we have already a lock on LOCK_open
+
+  NOTES
+    table->query_id will be 0 if table was reopened
+
+  RETURN
+    0  ok
+    1  error ('table' is unchanged if table couldn't be reopened)
 ****************************************************************************/
 
 bool reopen_table(TABLE *table,bool locked)
@@ -1085,8 +1095,10 @@ bool reopen_table(TABLE *table,bool locked)
     (*field)->table_name=table->table_name;
   }
   for (key=0 ; key < table->keys ; key++)
+  {
     for (part=0 ; part < table->key_info[key].usable_key_parts ; part++)
       table->key_info[key].key_part[part].field->table= table;
+  }
   VOID(pthread_cond_broadcast(&COND_refresh));
   error=0;
 

sql/sql_handler.cc

@@ -437,9 +437,14 @@ int mysql_ha_read(THD *thd, TABLE_LIST *tables,
   if (!lock)
     goto err0; // mysql_lock_tables() printed error message already
 
-  if (cond && ((!cond->fixed &&
-              cond->fix_fields(thd, tables, &cond)) || cond->check_cols(1)))
-    goto err0;
+  if (cond)
+  {
+    if (table->query_id != thd->query_id)
+      cond->cleanup();                          // File was reopened
+    if ((!cond->fixed &&
+         cond->fix_fields(thd, tables, &cond)) || cond->check_cols(1))
+      goto err0;
+  }
 
   if (keyname)
   {