Joe McDonnell created IMPALA-13179: -------------------------------------- Summary: Disable tuple caching when using non-deterministic functions Key: IMPALA-13179 URL: https://issues.apache.org/jira/browse/IMPALA-13179 Project: IMPALA Issue Type: Bug Components: Frontend Affects Versions: Impala 4.5.0 Reporter: Joe McDonnell
Some functions are non-deterministic, so tuple caching needs to detect those functions and avoid caching at locations that are non-deterministic. There are two different pieces: # Correctness: If the key is constant but the results can be variable, then that is a correctness issue. That can happen for genuinely random functions like uuid(). It can happen when timestamp functions like now() are evaluated at runtime. # Performance: The frontend does constant-folding of functions that don't vary during executions, so something like now() might be replaced by a hard-coded integer. This means that the key contains something that varies frequently. That can be a performance issue, because we can be caching things that cannot be reused. This doesn't have the same correctness issue. This ticket is focused on correctness piece. If uuid()/now()/etc are referenced and would be evaluated at runtime, the location should be ineligible for tuple caching. -- This message was sent by Atlassian Jira (v8.20.10#820010) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org