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From "Vladimir Ozerov (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (IGNITE-6877) Improve behaviour for non-correlated subqueries
Date Mon, 18 Feb 2019 07:15:01 GMT

     [ https://issues.apache.org/jira/browse/IGNITE-6877?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Vladimir Ozerov resolved IGNITE-6877.
    Resolution: Won't Fix  (was: Fixed)

> 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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