[jira] [Created] (IGNITE-8596) SQL: remove unnecessary index lookups when query parallelism is enabled

[Anton Vinogradov (Jira)]

Vladimir Ozerov created IGNITE-8596:
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             Summary: 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
             Fix For: 2.6


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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