In some failure scenarios, the data update for the base table may not be synchronized to the secondary index in time. If the failure time is long, this part of the update for the secondary index may even be lost, so how should we fix this part? What about inconsistent data?
nodetool repair to repair the keyspace, will the base table and secondary indexes(or materialized views) be repaired at the same time?
Repairing the keyspace will indeed repair both base tables and views/indexes and this might be enough to fix all inconsistencies. Note that this repair will not fix inconsistencies where a view/index update was completely lost and this is not present on any of the view/index replicas. To fix these kind of inconsistencies we would need a base-table ↔ view/index repair, which goes over each base table row and ensures the corresponding view/index row is correct. We did have proposals on how to fix it but nothing materialized out of it yet. Currently the only option for fixing such inconsistencies is to drop the view/index and re-create it from scratch.