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https://issues.apache.org/jira/browse/IGNITE-6085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16255155#comment-16255155
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Roman Kondakov commented on IGNITE-6085:
----------------------------------------
This problem occurs only with the OR condition in ON clause. If you change
condition to AND this query works well. The problem could be in the method
{code:java}
public void createIndexConditions(Session session, TableFilter filter) {
if (andOrType == AND) {
left.createIndexConditions(session, filter);
right.createIndexConditions(session, filter);
}
}
{code}
in ConditionAndOr class. I asked a question about it in H2/issues:
https://github.com/h2database/h2database/issues/670. Waiting for a response now.
> SQL: JOIN with multiple conditions is extremely slow
> ----------------------------------------------------
>
> Key: IGNITE-6085
> URL: https://issues.apache.org/jira/browse/IGNITE-6085
> Project: Ignite
> Issue Type: Task
> Components: sql
> Affects Versions: 2.1
> Reporter: Vladimir Ozerov
> Assignee: Roman Kondakov
> Labels: performance
> Fix For: 2.4
>
>
> Consider the following query:
> {code}
> SELECT ... FROM A a
> INNER JOIN B b ON b.id = a.foreign_id1 OR b.id = a.foreign_id2
> {code}
> In this case H2 cannot use indexes on {{foreign_id1}} or {{foreign_id2}}
> columns and query execution takes extraordinary time. Known workaround for a
> problem is to apply multiple JOINs, e.g.:
> {code}
> SELECT ... FROM A a
> LEFT OUTER JOIN B b1 ON b1.id = a.foreign_id1
> LEFT OUTER JOIN B b2 ON b2.id = a.foreign_id2
> WHERE b1.id IS NOT NULL AND b2.id IS NOT NULL
> {code}
> On a single real-world scenario it improved exeution time by a factor of 500
> (from 4s to 80ms).
> Something is terribly wrong here. Probably, H2 cannot perform necessary query
> re-write, or cannot understand how to use index. Let's find a way to fix that.
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