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From "Vladimir Ozerov (JIRA)" <j...@apache.org>
Subject [jira] [Created] (IGNITE-6024) SQL: execute DML statements on the server when possible
Date Thu, 10 Aug 2017 09:06:00 GMT
Vladimir Ozerov created IGNITE-6024:
---------------------------------------

             Summary: 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: Improvement
          Components: sql
    Affects Versions: 2.1
            Reporter: Vladimir Ozerov
             Fix For: 2.2


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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