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https://issues.apache.org/jira/browse/IGNITE-6877?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16879385#comment-16879385
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Denis Mekhanikov commented on IGNITE-6877:
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No other tickets for this issue have been created yet, but the problem is still
present. So, I'm for keeping the ticket open.
Feel free to close as a duplicate, when another one is created.
> Improve behaviour for non-correlated subqueries
> -----------------------------------------------
>
> Key: IGNITE-6877
> URL: https://issues.apache.org/jira/browse/IGNITE-6877
> Project: Ignite
> Issue Type: Improvement
> Components: sql
> Affects Versions: 2.3
> Reporter: Alin Andrei Corodescu
> Priority: Minor
>
> Ignite behaves poorly in terms of performance when given queries which
> contain IN or = operators followed by a non-correlated subquery. My guess is
> that the query is actually run for each row of the table in order to test the
> condition.
> A possible solution is to store the results of the subquery in a temporary
> table, and use it from there.
> A workaround at the moment is to use joins instead of IN or = operators, but
> this makes the query much more complicated.
> Example:
> SELECT name
> FROM Employees
> WHERE age IN (SELECT age FROM Customers)
> The performance of this query is very slow for small amounts of data (about
> 20 seconds for 4000 rows in each table last time I tried)
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