[FLINK-12820] Support ignoring null fields when writing to Cassandra

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.8.0
• Fix Version/s: 1.9.0
• Component/s: Connectors / Cassandra
• Labels: pull-request-available
• Assignee: Unassigned
• Reporter: Ozan Cicekci
• Created: 12/Jun/19 12:19
• Updated: 05/Jul/19 07:01
• Resolved: 05/Jul/19 07:01

Description

Currently, records which have null fields are written to their corresponding columns in Cassandra as null. Writing null is basically a 'delete' for Cassandra, it's useful if nulls should correspond to deletes in the data model, but nulls can also indicate a missing data or partial column update. In that case, we end up overwriting columns of existing record on Cassandra with nulls. 

 

I believe it's already possible to ignore null values for POJO's with mapper options, as documented here:

https://ci.apache.org/projects/flink/flink-docs-stable/dev/connectors/cassandra.html#cassandra-sink-example-for-streaming-pojo-data-type

 

But this is not possible when using scala tuples or case classes. Perhaps with a Cassandra sink configuration flag, null values can be unset using below option for tuples and case classes.

https://docs.datastax.com/en/drivers/java/3.0/com/datastax/driver/core/BoundStatement.html#unset-int-

 

Here is the equivalent configuration in spark-cassandra-connector;

https://github.com/datastax/spark-cassandra-connector/blob/master/doc/5_saving.md#globally-treating-all-nulls-as-unset

Issue Links

• links to: GitHub Pull Request #8714