[CASSANDRA-12910] SASI: calculatePrimary() always returns null

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 3.11.0
• Component/s: Feature/SASI
• Severity: Low
• Assignee: Corentin Chary
• Reporter: Corentin Chary

Authors

Corentin Chary

Reviewers

Alex Petrov

• Created: 14/Nov/16 08:06
• Updated: 16/Apr/19 09:30
• Resolved: 07/Dec/16 15:54

Description

While investigating performance issues with SASI (https://github.com/criteo/biggraphite/issues/174 if you want to know more) I ended finding calculatePrimary() in QueryController.java which apparently should return the "primary index".

It lacks documentation, and I'm unsure what the "primary index" should be, but apparently this function never returns one because primaryIndexes.size() is always 0.

https://github.com/apache/cassandra/blob/81f6c784ce967fadb6ed7f58de1328e713eaf53c/src/java/org/apache/cassandra/index/sasi/plan/QueryController.java#L237

I'm unsure if the proper fix is checking if the collection is empty or reversing the operator (selecting the index with higher cardinality versus the one with lower cardinality).