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https://issues.apache.org/jira/browse/IGNITE-8596?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Mashenkov reassigned IGNITE-8596:
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Assignee: Andrew Mashenkov
> SQL: remove unnecessary index lookups when query parallelism is enabled
> -----------------------------------------------------------------------
>
> Key: IGNITE-8596
> URL: https://issues.apache.org/jira/browse/IGNITE-8596
> Project: Ignite
> Issue Type: Task
> Components: sql
> Affects Versions: 2.5
> Reporter: Vladimir Ozerov
> Assignee: Andrew Mashenkov
> Priority: Major
> Labels: performance
> Fix For: 2.7
>
>
> See
> {{org.apache.ignite.internal.processors.query.h2.twostep.GridMapQueryExecutor#onQueryRequest}}
> method. If table is segmented, we will submit as many SQL requests as much
> segments. But consider a case when target cache partition(s) is already
> defined by user or derived through partition pruning. In this case most of
> segments will not contain useful information and return empty result set. At
> the same time these queries may impose index or data page scans, thus
> consuming resources without a reason.
> To mitigate the problem we should not submit SQL requests to segments we are
> not interested in.
> Note that it is not sufficient to simply skip SQL requests on mapper, because
> reducer expects separate response for every message. We should fix both local
> mapper logic as well as protocol.
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