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Sahil Takiar commented on IMPALA-9225: -------------------------------------- Nice work on this! > Retryable queries should spool all results before returning any to the client > ----------------------------------------------------------------------------- > > Key: IMPALA-9225 > URL: https://issues.apache.org/jira/browse/IMPALA-9225 > Project: IMPALA > Issue Type: Sub-task > Reporter: Sahil Takiar > Assignee: Quanlong Huang > Priority: Critical > Fix For: Impala 4.0 > > > If query retries are enabled, a query should not return any results to the > client until all results are spooled. The issue is that once a query starts > returning results, retrying the query becomes increasingly complex and is not > supported in the initial version of IMPALA-9124. Retrying a query while > returning results could cause incorrect results, especially for > non-deterministic queries (e.g. when the results are not ordered). > Since a query can fail anytime while results are being produced, transparent > retries are most effective if they can be done during any point of query > execution. > The one edge case is what happens if all query results cannot be contained in > the allocated result spooling memory (including unpinned memory). In this > case, retries for the query should be transparently disabled. > We should consider making this configurable, in case it leads to performance > degradation. Although, I'm inclined to turn the flag on by default (e.g. > always spool all returns before returning them), otherwise (depending on the > query) query retries won't always be helpful. -- This message was sent by Atlassian Jira (v8.3.4#803005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org