Remove rec_get_nth_def_field()

The function had only one caller.

storage/innobase/include/rem0rec.h

@@ -822,31 +822,6 @@ inline bool rec_is_delete_marked(const rec_t* rec, ulint comp)
 		== REC_INFO_DELETED_FLAG;
 }
 
-/** Get the nth field from an index.
-@param[in]	rec	index record
-@param[in]	index	index
-@param[in]	offsets	rec_get_offsets(rec, index)
-@param[in]	n	field number
-@param[out]	len	length of the field in bytes, or UNIV_SQL_NULL
-@return a read-only copy of the index field */
-inline
-const byte*
-rec_get_nth_def_field(
-	const rec_t*		rec,
-	const dict_index_t*	index,
-	const ulint*		offsets,
-	ulint			n,
-	ulint*			len)
-{
-	ut_ad(rec_offs_validate(rec, index, offsets));
-	if (rec_offs_n_fields(offsets) > n
-	    && !rec_offs_nth_default(offsets, n)) {
-		return rec_get_nth_field(rec, offsets, n, len);
-	}
-
-	return index->instant_field_value(n - 1, len);
-}
-
 /** Get the nth field from an index.
 @param[in]	rec	index record
 @param[in]	index	index

storage/innobase/trx/trx0rec.cc

@@ -1122,9 +1122,17 @@ trx_undo_page_report_modify(
 
 				if (rec_is_alter_metadata(rec, index)) {
 					ut_ad(update->is_alter_metadata());
-					field = rec_get_nth_def_field(
-						rec, index, offsets, pos,
-						&flen);
+
+					field = rec_offs_n_fields(offsets)
+						> pos
+						&& !rec_offs_nth_default(
+							offsets, pos)
+						? rec_get_nth_field(
+							rec, offsets,
+							pos, &flen)
+						: index->instant_field_value(
+							pos - 1, &flen);
+
 					if (pos == index->first_user_field()) {
 						ut_ad(rec_offs_nth_extern(
 							offsets, pos));