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https://issues.apache.org/jira/browse/IMPALA-13276?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Fang-Yu Rao updated IMPALA-13276:
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Summary: Revise the documentation of query option
'RUNTIME_FILTER_WAIT_TIME_MS' (was: Revise the description of the query option
of 'RUNTIME_FILTER_WAIT_TIME_MS')
> Revise the documentation of query option 'RUNTIME_FILTER_WAIT_TIME_MS'
> ----------------------------------------------------------------------
>
> Key: IMPALA-13276
> URL: https://issues.apache.org/jira/browse/IMPALA-13276
> Project: IMPALA
> Issue Type: Task
> Components: Docs
> Reporter: Fang-Yu Rao
> Assignee: Fang-Yu Rao
> Priority: Major
>
> The documentation of the query option 'RUNTIME_FILTER_WAIT_TIME_MS' at
> [https://github.com/apache/impala/blob/master/docs/topics/impala_runtime_filter_wait_time_ms.xml#L37-L43]
> as provided in the following describes the meaning of this query option.
> {code:java}
> The <codeph>RUNTIME_FILTER_WAIT_TIME_MS</codeph> query option
> adjusts the settings for the runtime filtering feature.
> It specifies a time in milliseconds that each scan node waits for
> runtime filters to be produced by other plan fragments.
> {code}
>
> However the description above is not entirely accurate in that the wait time
> is with respect to the time when a runtime filter was registered (within
> [QueryState::InitFilterBank()|https://github.com/apache/impala/blob/master/be/src/runtime/query-state.cc#L381])
> instead of the time when a scan node is calling
> [ScanNode::WaitForRuntimeFilters()|https://github.com/apache/impala/blob/master/be/src/exec/scan-node.cc#L212].
> For instance if a scan node started so late that when
> ScanNode::WaitForRuntimeFilters() was called, the amount of time passed since
> the registration of this runtime filter was already greater than the value of
> 'RUNTIME_FILTER_WAIT_TIME_MS', this scan node would not be waiting for the
> runtime filter. Refer to
> [https://github.com/apache/impala/blob/master/be/src/runtime/runtime-filter.cc#L86-L87]
> for further details.
> {code:java}
> bool RuntimeFilter::WaitForArrival(int32_t timeout_ms) const {
> unique_lock<mutex> l(arrival_mutex_);
> while (arrival_time_.Load() == 0) {
> int64_t ms_since_registration = MonotonicMillis() - registration_time_;
> int64_t ms_remaining = timeout_ms - ms_since_registration;
> if (ms_remaining <= 0) break;
> if (injection_delay_ > 0) SleepForMs(injection_delay_);
> arrival_cv_.WaitFor(l, ms_remaining * MICROS_PER_MILLI);
> }
> return arrival_time_.Load() != 0;
> }
> {code}
> We should revise the documentation to make it a bit clearer.
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