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https://issues.apache.org/jira/browse/IMPALA-14271?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Work on IMPALA-14271 started by Joe McDonnell.
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> Tuple caching gets stuck waiting for a runtime filter that will never arrive
> ----------------------------------------------------------------------------
>
> Key: IMPALA-14271
> URL: https://issues.apache.org/jira/browse/IMPALA-14271
> Project: IMPALA
> Issue Type: Task
> Components: Backend, Frontend
> Affects Versions: Impala 5.0.0
> Reporter: Joe McDonnell
> Assignee: Joe McDonnell
> Priority: Major
>
> In benchmarking with the cost based placement, for a couple queries, some
> fragments get stuck waiting for runtime filters. In particular, Q5 for TPC-H
> and Q61 for TPC-DS get stuck. They time out of the wait after 5 seconds,
> which this is a significant performance regression.
> The runtime filters that they are waiting for are remote, so they pass
> through the coordinator. The problem is that if the query returns results
> quickly, the coordinator will transition from EXECUTING to RETURNED_RESULTS.
> The code that is processing the runtime filter on the coordinator in
> Coordinator::UpdateFilter() will bail out if the query is no longer executing:
> {noformat}
> if (!IsExecuting()) {
> LOG(INFO) << "Filter update received for non-executing query with id: "
> << PrintId(query_id());
> return;
> }{noformat}
> The fragment that is waiting on the runtime filter won't receive it, so it
> waits until it hits the runtime filter wait time or the query is cancelled.
> The problem is that this doesn't happen until seconds later.
> One solution for this is to reapply the core logic from IMPALA-6984 (i.e.
> reverting IMPALA-10047). That immediately sends a cancel when the query
> transitions to RETURNED_RESULTS.
> This should only be a problem if all fragment instances hit the tuple cache.
> If one fragment instance does not, then the query won't transition to
> RETURNED_RESULTS before the runtime filter is processed, because the fragment
> instance still needs the hash table.
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