[CASSANDRA-15910] Add multi-partition key commands

• Type: Improvement
• Status: Triage Needed
• Priority: Normal
• Resolution: Unresolved
• Labels: query read
• Platform: All
• Assignee: Unassigned
• Reporter: Andres de la Peña
• Created: 01/Jul/20 16:14
• Updated: 01/Jul/20 16:22

Description

As it's mentioned in this TODO comment that was introduced in CASSANDRA-8272, replica filtering protection would benefit from a ReadCommand implementation able to internally read the rows identified by a group of primary keys residing in different partitions.

It would be different from SinglePartitionReadCommand.Group in that it wouldn't need to be split in per-partition commands when sending it to a replica. We could call it MultiPartitionReadCommand, for example.

Such command would also be beneficial for the performance of regular IN CQL queries, since it would reduce the traffic between the coordinator and the replicas by grouping the queries sent to a replica.

An alternative way of getting that performance gain could be modifying how the current SinglePartitionReadCommand.Group is executed on the StorageProxy so, instead of sending each of its internal SinglePartitionReadCommand s to the replicas, we could split it in smaller Group commands targeted to specific replicas, if that makes sense.

Issue Links

• is related to: CASSANDRA-8272 2ndary indexes can return stale data
• is related to: CASSANDRA-15907 Operational Improvements & Hardening for Replica Filtering Protection