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https://issues.apache.org/jira/browse/CALCITE-1920?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16112394#comment-16112394
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Julian Hyde commented on CALCITE-1920:
--------------------------------------
It might be worth writing a test case to make sure that you get the behavior
you want in, say, RelOptRulesTest. I can see that converting
{code}SELECT * FROM t1 JOIN (SELECT DISTINCT k FROM t2) USING (k){code}
to
{code}SELECT * FROM t1 JOIN (SELECT DISTINCT k FROM t2 WHERE k IS NOT NULL)
USING (k){code}
might improve the query significantly.
> Add IS_NOT_NULL predicate on not-nullable equi-join keys
> --------------------------------------------------------
>
> Key: CALCITE-1920
> URL: https://issues.apache.org/jira/browse/CALCITE-1920
> Project: Calcite
> Issue Type: Improvement
> Affects Versions: 1.13.0
> Reporter: Ted Xu
> Assignee: Julian Hyde
>
> In equi-joins, if the join keys are not-nullable according to join type, we
> can assign a IS_NOT_NULL predicate to reduce input. For example, query:
> {code:sql}
> select * from src1 join src2 on src1.id = src2.id
> {code}
> can be rewrite to
> {code:sql}
> select * from
> (select * from src1 where src1.id is not null) src1
> join
> (select * from src2 where src2.id is not null) src2
> on src1.id = src2.id
> {code}
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