diff --git a/sql/sql_class.h b/sql/sql_class.h
index 6bbcca65166..fa63cd90976 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -492,7 +492,10 @@ public:
   CHANGED_TABLE_LIST * changed_table_dup(TABLE *table);
 };
 
-
+/*
+  Used to hold information about file and file structure in exchainge 
+  via non-DB file (...INTO OUTFILE..., ...LOAD DATA...)
+*/
 class sql_exchange :public Sql_alloc
 {
 public:
diff --git a/sql/table.h b/sql/table.h
index 16a42cd58a4..209333c24b7 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -112,7 +112,7 @@ struct st_table {
   char		*table_name,*real_name,*path;
   uint		key_length;		/* Length of key */
   uint		tablenr,used_fields,null_bytes;
-  table_map	map;
+  table_map	map;                    /* ID bit of table (1,2,4,8,16...) */
   ulong		version,flush_version;
   uchar		*null_flags;
   IO_CACHE	*io_cache;			/* If sorted trough file*/
@@ -141,13 +141,14 @@ typedef struct st_table_list {
   uint32        db_length, real_name_length;
   Item		*on_expr;			/* Used with outer join */
   struct st_table_list *natural_join;		/* natural join on this table*/
-  List<String>	*use_index,*ignore_index;
+  /* ... join ... USE INDEX ... IGNORE INDEX */
+  List<String>	*use_index,*ignore_index; 
   TABLE		*table;
   GRANT_INFO	grant;
   thr_lock_type lock_type;
   uint		outer_join;			/* Which join type */
   bool		straight;			/* optimize with prev table */
-  bool          updating;     /* for replicate-do/ignore table */
+  bool          updating;                   /* for replicate-do/ignore table */
   bool		shared;				/* Used twice in union */
 } TABLE_LIST;