Behavioral Changes in Impala

Behavioral changes denote a marked change in behavior from the previously released version to this version of Apache Impala.

Summary:

Impala now unregisters timed-out queries promptly to free memory, retaining error messages for clients that return later.

Previous behavior:

Timed-out queries remained registered until the session closed, keeping memory occupied and sometimes leaving failed queries in an active state if not explicitly closed.

New behavior:

Timed-out queries are unregistered immediately to free memory, while error messages are kept in a new structure so clients can still receive an error message if they return later.

Apache Jira: IMPALA-12602