[jira] [Resolved] (OPTIQ-367) PushFilterPastJoinRule should strengthen join type

["Julian Hyde (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/OPTIQ-367?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde resolved OPTIQ-367.
-------------------------------

    Resolution: Fixed

Fixed in http://git-wip-us.apache.org/repos/asf/incubator-optiq/commit/201d5917.

> PushFilterPastJoinRule should strengthen join type
> --------------------------------------------------
>
>                 Key: OPTIQ-367
>                 URL: https://issues.apache.org/jira/browse/OPTIQ-367
>             Project: Optiq
>          Issue Type: Bug
>            Reporter: Julian Hyde
>            Assignee: Julian Hyde
>
> PushFilterPashJoinRule can already convert a filter on a join into a join. (For example, 'FROM emp JOIN dept ON TRUE WHERE emp.deptno = emp.deptno' into 'FROM emp JOIN dept ON emp.deptno = dept.deptno'.)
> But if the filter is strong -- i.e. it is guaranteed to return false if one of its input values is NULL -- then we can upgrade the join type. For example,
> {code}
> FROM emp FULL JOIN dept WHERE emp.age > 30
> {code}
> becomes
> {code}
> FROM emp LEFT JOIN dept WHERE emp.age > 30
> {code}
> The condition is strong on emp.age, and emp.age comes from the left, so that if a null row is generated on the left the condition will fail. Therefore we can strengthen the join type to LEFT, which only generates nulls on the right.
> I also want to work on the kind of queries produced by EXISTS/IN rewrite; for example, the query in RelOptRulesTest.testSemiJoinRule
> {code}
>     FilterRel(condition=[IS TRUE($3)])
>       JoinRel(condition=[=($0, $2)], joinType=[left])
>         TableAccessRel(table=[[CATALOG, SALES, DEPT]])
>         AggregateRel(group=[{0}], agg#0=[MIN($1)])
>           ...
> {code}
> should become
> {code}
>     JoinRel(condition=[=($0, $2) AND IS TRUE($3)], joinType=[inner])
>       TableAccessRel(table=[[CATALOG, SALES, DEPT]])
>       AggregateRel(group=[{0}], agg#0=[MIN($1)])
>         ...
> {code}



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