branches/zip: row_ext_create(), row_ext_lookup(): Clarify that the

column numbers are relative to the InnoDB table object, or numbers
returned by dict_col_get_no().  This will have to be ensured in
all calling code.

include/row0ext.h

@@ -22,7 +22,9 @@ row_ext_create(
 				/* out,own: column prefix cache */
 	ulint		n_ext,	/* in: number of externally stored columns */
 	const ulint*	ext,	/* in: col_no's of externally stored columns
-				in the clustered index record */
+				in the InnoDB table object, as reported by
+				dict_col_get_no(); NOT relative to the records
+				in the clustered index */
 	ulint		zip_size,/* compressed page size, or 0 */
 	mem_heap_t*	heap);	/* in: heap where created */
 
@@ -49,8 +51,10 @@ row_ext_lookup(
 				/* out: column prefix, or NULL if
 				the column is not stored externally */
 	row_ext_t*	ext,	/* in/out: column prefix cache */
-	ulint		col,	/* in: column number
-				in the clustered index record */
+	ulint		col,	/* in: column number in the InnoDB
+				table object, as reported by
+				dict_col_get_no(); NOT relative to the
+				records in the clustered index */
 	const byte*	field,	/* in: locally stored part of the column */
 	ulint		f_len,	/* in: length of field, in bytes */
 	ulint*		len);	/* out: length of prefix, in bytes,

include/row0ext.ic

@@ -31,7 +31,9 @@ row_ext_create(
 				/* out,own: column prefix cache */
 	ulint		n_ext,	/* in: number of externally stored columns */
 	const ulint*	ext,	/* in: col_no's of externally stored columns
-				in the clustered index record */
+				in the InnoDB table object, as reported by
+				dict_col_get_no(); NOT relative to the records
+				in the clustered index */
 	ulint		zip_size,/* compressed page size, or 0 */
 	mem_heap_t*	heap)	/* in: heap where created */
 {
@@ -91,8 +93,10 @@ row_ext_lookup(
 				/* out: column prefix, or NULL if
 				the column is not stored externally */
 	row_ext_t*	ext,	/* in/out: column prefix cache */
-	ulint		col,	/* in: column number
-				in the clustered index record */
+	ulint		col,	/* in: column number in the InnoDB
+				table object, as reported by
+				dict_col_get_no(); NOT relative to the
+				records in the clustered index */
 	const byte*	field,	/* in: locally stored part of the column */
 	ulint		f_len,	/* in: length of field, in bytes */
 	ulint*		len)	/* out: length of prefix, in bytes,