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https://issues.apache.org/jira/browse/IOTDB-4005?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yuan Tian reassigned IOTDB-4005:
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Assignee: Alima777 (was: Yuan Tian)
> Parallel the FragmentInstance execution
> ---------------------------------------
>
> Key: IOTDB-4005
> URL: https://issues.apache.org/jira/browse/IOTDB-4005
> Project: Apache IoTDB
> Issue Type: Improvement
> Components: Core/Query
> Reporter: Yuan Tian
> Assignee: Alima777
> Priority: Major
>
> Previously, we accelerate raw query data without value filter by split each
> sensor's scan execution into a thread pool, in this way, we can accelerate
> the decompress and decode phase in query processing.
> In current mpp, we only run one fragmentInstance in one thread, so all
> sensors in that FragmentInstance will only scan, decompress and decode one by
> one which cause the query performance won't reach the previous level.
> We need to rethink about how to parallel our FragmentInstance, and meanwhile
> we should also take memory control into account, the previous version may
> cause OOM problem while there exists too many sensors in one query.
> We should also take deadlock into account while doing memory controlling, in
> case of one sensor occupying all the remaining usable memory, another sensor
> can never get more memory, but the whole query must wait for each sensor
> returning at least one TsBlock.
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