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From "Vladimir Ozerov (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (IGNITE-8596) SQL: remove unnecessary index lookups when query parallelism is enabled
Date Tue, 29 Jan 2019 08:23:00 GMT

     [ https://issues.apache.org/jira/browse/IGNITE-8596?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vladimir Ozerov updated IGNITE-8596:
------------------------------------
    Labels: performance  (was: iep-24 performance)

> 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: Improvement
>          Components: sql
>    Affects Versions: 2.5
>            Reporter: Vladimir Ozerov
>            Assignee: Andrew Mashenkov
>            Priority: Major
>              Labels: performance
>             Fix For: 2.8
>
>
> 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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