Bug#53812: assert row/row0umod.c line 660 in txn rollback after crash recovery

row_undo_mod_upd_exist_sec(): Tolerate a failure to build the index entry
for a DYNAMIC or COMPRESSED table during crash recovery.

storage/innodb_plugin/row/row0umod.c

@@ -657,33 +657,63 @@ row_undo_mod_upd_exist_sec(
 			/* Build the newest version of the index entry */
 			entry = row_build_index_entry(node->row, node->ext,
 						      index, heap);
-			ut_a(entry);
+			if (UNIV_UNLIKELY(!entry)) {
+				/* The server must have crashed in
+				row_upd_clust_rec_by_insert(), in
+				row_ins_index_entry_low() before
+				btr_store_big_rec_extern_fields()
+				has written the externally stored columns
+				(BLOBs) of the new clustered index entry. */
+
+				/* The table must be in DYNAMIC or COMPRESSED
+				format.  REDUNDANT and COMPACT formats
+				store a local 768-byte prefix of each
+				externally stored column. */
+				ut_a(dict_table_get_format(index->table)
+				     >= DICT_TF_FORMAT_ZIP);
+
+				/* This is only legitimate when
+				rolling back an incomplete transaction
+				after crash recovery. */
+				ut_a(thr_get_trx(thr)->is_recovered);
+
+				/* The server must have crashed before
+				completing the insert of the new
+				clustered index entry and before
+				inserting to the secondary indexes.
+				Because node->row was not yet written
+				to this index, we can ignore it.  But
+				we must restore node->undo_row. */
+			} else {
 				/* NOTE that if we updated the fields of a
 				delete-marked secondary index record so that
 				alphabetically they stayed the same, e.g.,
-			'abc' -> 'aBc', we cannot return to the original
-			values because we do not know them. But this should
-			not cause problems because in row0sel.c, in queries
-			we always retrieve the clustered index record or an
-			earlier version of it, if the secondary index record
-			through which we do the search is delete-marked. */
-
-			err = row_undo_mod_del_mark_or_remove_sec(node, thr,
-								  index,
-								  entry);
+				'abc' -> 'aBc', we cannot return to the
+				original values because we do not know them.
+				But this should not cause problems because
+				in row0sel.c, in queries we always retrieve
+				the clustered index record or an earlier
+				version of it, if the secondary index record
+				through which we do the search is
+				delete-marked. */
+
+				err = row_undo_mod_del_mark_or_remove_sec(
+					node, thr, index, entry);
 				if (err != DB_SUCCESS) {
 					mem_heap_free(heap);
 
 					return(err);
 				}
 
+				mem_heap_empty(heap);
+			}
+
 			/* We may have to update the delete mark in the
 			secondary index record of the previous version of
 			the row. We also need to update the fields of
 			the secondary index record if we updated its fields
 			but alphabetically they stayed the same, e.g.,
 			'abc' -> 'aBc'. */
-			mem_heap_empty(heap);
 			entry = row_build_index_entry(node->undo_row,
 						      node->undo_ext,
 						      index, heap);