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From "Alexander Paschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IGNITE-6024) SQL: execute DML statements on the server when possible
Date Wed, 11 Oct 2017 10:33:00 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-6024?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16200080#comment-16200080
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Alexander Paschenko commented on IGNITE-6024:
---------------------------------------------

[~isapego], OK, let's let that be.

> SQL: execute DML statements on the server when possible
> -------------------------------------------------------
>
>                 Key: IGNITE-6024
>                 URL: https://issues.apache.org/jira/browse/IGNITE-6024
>             Project: Ignite
>          Issue Type: Task
>          Components: sql
>    Affects Versions: 2.1
>            Reporter: Vladimir Ozerov
>            Assignee: Sergey Kalashnikov
>              Labels: important, performance
>             Fix For: 2.3
>
>
> Currently we execute DML statements as follows:
> 1) Get query result set to the client
> 2) Construct entry processors and send them to servers in batches
> This approach is inefficient as it causes a lot of unnecessary network communication
 Instead, we should execute DML statements directly on server nodes when it is possible.
> Implementation considerations:
> 1) Determine set of queries which could be processed in this way. E.g., {{LIMIT/OFFSET}},
{{GROUP BY}}, {{ORDER BY}}, {{DISTINCT}}, etc. are out of question - they must go through
the client anyway. Probably {{skipMergeTable}} flag is a good starting point (good, not precise!)
> 2) Send request to every server and execute local DML right there
> 3) No failover support at the moment - throw "partial update" exception if topology is
unstable
> 4) Handle partition reservation carefully
> 5) Transactions: we still have single coordinator - this is a client. When MVCC and TX
SQL is ready, client will assign proper counters to server requests.



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