Fix innodb.instant_alter_crash

row_undo_mod_parse_undo_rec(): Handle both types of metadata records.

row_upd_index_replace_metadata(): Correctly process DB_TRX_ID,DB_ROLL_PTR,
and assert that a new value for the metadata BLOB is present.

storage/innobase/row/row0umod.cc

@@ -1237,17 +1237,21 @@ row_undo_mod_parse_undo_rec(
 	ut_ad(!node->ref->info_bits);
 
 	if (node->update->info_bits & REC_INFO_MIN_REC_FLAG) {
-		/* This must be an undo log record for a subsequent
-		instant ALTER TABLE, extending the metadata record. */
-		ut_ad(clust_index->is_instant());
-		if (node->update->info_bits != REC_INFO_MIN_REC_FLAG) {
+		if ((node->update->info_bits & ~REC_INFO_DELETED_FLAG)
+		    != REC_INFO_MIN_REC_FLAG) {
 			ut_ad(!"wrong info_bits in undo log record");
 			goto close_table;
 		}
-		// FIXME: Could be REC_INFO_METADATA_ALTER as well?
-		node->update->info_bits = REC_INFO_METADATA_ADD;
-		const_cast<dtuple_t*>(node->ref)->info_bits
-			= REC_INFO_METADATA_ADD;
+		/* This must be an undo log record for a subsequent
+		instant ALTER TABLE, extending the metadata record. */
+		ut_ad(clust_index->is_instant());
+		ut_ad(clust_index->table->instant
+		      || !(node->update->info_bits & REC_INFO_DELETED_FLAG));
+		const_cast<dtuple_t*>(node->ref)->info_bits =
+			node->update->info_bits = (node->update->info_bits
+						   & REC_INFO_DELETED_FLAG)
+			? REC_INFO_METADATA_ALTER
+			: REC_INFO_METADATA_ADD;
 	}
 
 	if (!row_undo_search_clust_to_pcur(node)) {

storage/innobase/row/row0upd.cc

@@ -1341,15 +1341,17 @@ row_upd_index_replace_metadata(
 	ut_ad(entry->n_fields == ulint(index->n_fields) + 1);
 	const page_size_t& page_size = dict_table_page_size(index->table);
 	const ulint first = index->first_user_field();
+	ut_d(bool found_mblob = false);
 
 	for (ulint i = upd_get_n_fields(update); i--; ) {
 		const upd_field_t* uf = upd_get_nth_field(update, i);
 		ut_ad(!upd_fld_is_virtual_col(uf));
-		ut_ad(uf->field_no >= first);
+		ut_ad(uf->field_no >= first - 2);
 		ulint f = uf->field_no;
 		dfield_t* dfield = dtuple_get_nth_field(entry, f);
 
-		if (f-- == first) {
+		if (f == first) {
+			ut_d(found_mblob = true);
 			ut_ad(!dfield_is_ext(&uf->new_val));
 			ut_ad(!dfield_is_null(&uf->new_val));
 			ut_ad(dfield_is_ext(dfield));
@@ -1359,10 +1361,13 @@ row_upd_index_replace_metadata(
 			continue;
 		}
 
+		f -= f > first;
 		const dict_field_t* field = dict_index_get_nth_field(index, f);
 		row_upd_index_replace_new_col_val(dfield, field, field->col,
 						  uf, heap, page_size);
 	}
+
+	ut_ad(found_mblob);
 }
 
 /** Apply an update vector to an index entry.